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Publications of Prof. Dr.-Ing. habil. Volker Schulze

Peer-reviewed articles in journals

[ 1 ] Fleischer, J.; Löhe, D.; Kotschenreuther, J.; Schulze, V.; Deuchert, M. & Halvadjiysky, G. (2007), "Fertigungsverfahren in der Mikrotechnik", wt Werkstattstechnik online, no. 11, pp. 847-851.
Abstract:
Die zunehmende Miniaturisierung von Bauteilen führt zu großen Herausforderungen bei der Strukturierung von Mikrowerkzeugen. Mikrofräsen, Mikrofunkenerosion (EDM - Electrical Discharge Machining)und Laserablation sind in der Mikrotechnik geeignete Verfahren zur flexiblen Fertigung von Abformwerkzeugen für das Mikropulverspritzgießen aus hochfesten und verschleißbeständigen Werkstoffen. Je nach Zielsetzung liefert das einzelne oder eine Kombination mehrerer Verfahren die optimale Strategie zur bestmöglichen Oberflächenqualität.


[ 2 ] Fleischer, J.; Schulze, V.; Kotschenreuther, J.; Deuchert, M.; Löhe, D. & Zum Gahr, K. H. (2008), "Mechanical structuring, surface treatment and tribological characterization of steel mould inserts for micro powder injection moulding", Microsystem Technologies, pp. 1-7.
Abstract:
Manufacturing of ceramic and metallic micro components in micro powder injection moulding (ìPIM) requires mould inserts offering high wear resistance and a sufficient demoulding behaviour. Within the frame of this research ìPIM mould inserts made from low and high alloyed tool steel were structured by micro milling and finished by micro peening and ultrasonic wet peening. Influence of surface condition on wear and demoulding behaviour of the steels in ìPIM with ceramic feedstock was characterized using a laboratory tribotester simulating powder injection moulding and a specially adapted static friction tester. Results indicate that performance of mould inserts in micro powder injection moulding depends not only on hardness, surface condition and homogeneity of the mould insert materials but also is strongly influenced by the characteristics of the feedstock, like composition of the binder or amount and hardness of the ceramic particles.


[ 3 ] Schulze, V.; Michna, J.; Pabst, R. & Hauer, T. (2009), "Thermische Belastung beim Stirnplanfräsen", wt Werkstattstechnik online, no. 4, pp. 281-286.
Abstract:
Der Fachaufsatz beschreibt eine Methode zur Quantifizierung der thermischen Belastung bei der Trockenbearbeitung von EN-GJL-250 wie sie am Institut für Produktionstechnik (wbk) der Universität Karlsru he (TH) Anwendung findet. Im Fokus der Versuche steht die mathematische Beschreibung der Wärmestromdichte beim Gleichlauf-, Gegenlauf- und Querlauffräsen. Ziel der Forschungstätigkeit ist die Einbindung der Ergebnisse in ein mathematisches Modell als Eingangsgröße für Simulationsprogramme.
This paper describes an approach for quantifying the thermal impact during dry processing of EN-GJL-250 at the Institute of Production Scien ce (wbk) at the University of Karlsruhe. The experiments are focus ing on the mathematical specification of the heat flux during up-cut , down-cut and transversal milling. This project aims involving the results in a mathematical model as an input parameter for simulati on tools.


[ 4 ] Schulze, V.; Haupt, S. & Weber, P. (2009), "Hybrid machining of microstructures using a combination of electricaldischarge machining milling and laser ablation", Journal of Vacuum Science & Technology B (JVST B) - Microelectronics and Nanometer Structures, vol. 27, pp. 1327-1329.
Abstract:
Using laser beam machining with ultrashort laser pulses, microstructures in the micrometer region can be manufactured in virtually all materials, regardless of their mechanical properties. However, machining times are slow if good surface qualities are required. Micro electrical discharge machining (EDM) is also capable of removing material nearly without process forces, but with a higher processing speed if structure sizes exceed a certain value. With the combination of both processes, specific advantages can be realized while disadvantages can be partially eliminated. Therefore, a hybrid machine tool was developed that combines the two processes of ultrashort pulsed laser ablation and EDM milling. No reclamping is necessary. In this study, the limitations and challenges of the single processes are investigated. After that, the novel hybrid machine tool is presented, along with strategies for the efficient and economic manufacturing of microstructures in materials that are difficult to machine by conventional processes.


[ 5 ] Schulze, V.; Michna, J. & Pabst, R. (2010), "Mathematische Modellierung des Wärmeeintrags beim Fräsen", wt Werkstattstechnik online, no. 1, pp. 62-66.
Abstract:
In diesem Fachaufsatz wird ein mathematisches Modell zur Beschreibung des Wärmeeintrags in das Bauteil bei der trockenen Fräsbearbeitung vorgestellt. Das auf einem Potenzansatz basierende Modell berücksichtigt die Parameter Schnittgeschwindigkeit, Vorschub, Schnitttiefe, Eingriffsbreite, Schneideckenradius und Spanwinkel. Ziel der Forschungstätigkeit ist die Nutzung des Modells zur Generierung von Eingangsdaten für die Simulation des thermo-mechanischen Verhaltens komplexer Bauteile bei ihrer Herstellung.
This paper presents a mathematical model describing the heat input into the work-piece for dry milling. The model is based on a power law approach and reflects the parameters cutting speed, feed, cutting depth, cutting width, radius of the cutting edge and cutting angle. The aim of the research is to use the model for the generation of input data for the simulation of the thermo-mechanical behavior of complex work-pieces during their production.


[ 6 ] Schulze, V.; Weber, P.; Deuchert, M.; Haupt, S.; Ruhs, C. & Kienzler, A. (2010), "Limits and challenges of manufacturing micro molds", International Journal of Nanomanufacturing, vol. 6, pp. 176-189.
Abstract:
Due to the ongoing miniaturisation in industrial sectors like automotive, electronics or medical, the development of new manufacturing processes which are suitable for micro system technologies gains more and more importance. The miniaturisation of components leads to challenges in the manufacturing of micro parts. One application area is the manufacturing of moulds for the micro powder injection moulding (ìPIM) process. This process requires good surface qualities and a sufficient demoulding behaviour of the moulds. Micro milling, micro electrical discharge machining (ìEDM) and micro laser beam machining (ìLBM) are appropriate processes for the manufacturing of micro structures in different materials. Abrasive micro peening can be used for further precision treatment. Depending on the desired structure a single process or the combination of several processes has to be chosen to obtain superior surface qualities of the moulds. This paper deals with challenges and limits of the manufacturing processes among others exemplified on a gearwheel mould.


[ 7 ] Lanza, G.; Schulze, V.; Stockey, S.; Chlipala, M. & Peters, J. (2010), "Detection of shape deviations and measurement errorsby a point cloud analysis", Production Engineering - Research and Development, no. 6, pp. 599-605.
Abstract:
For the enhancement of technical workpiece surfaces with even larger dimensions, the application of microstructures on the surface is an appropriate way to improve the fitness for use without changing the properties of the basic material. Considering the extremely small dimensions of approximately 5–20 μm of the applied microstructure, the quality assurance faces new challenges related to the obtainment and evaluation of measurement data. This article presents an approach for the automated detection of shape deviations of a microstructure, as well as the detection of measurement errors during an optical or tactile measurement. The explained algorithm is based on the analysis of the measurement points within a point cloud by observing the distances between the single points. To illustrate the disturbance in the measurement point cloud every point is evaluated by an adaptive weighting function. The weighting of each measurement point can then be visualized by plotting the whole point cloud according to a corresponding color scale. The suitability of the point cloud analysis is demonstrated by the examples of a shape deviation (artificial groove) and a measurement error, occurred by measurement via confocal microscopy.


[ 8 ] Schulze, V.; Becke, C.; Weidenmann, K. A. & Dietrich, S. (2011), "Machining Strategies for Hole Making in Composites with Minimal Workpiece Damage by Directing the Process Forces Inwards", Journal of Materials Processing Technology, vol. 211, pp. 329-338.
Abstract:
Mechanical machining of fiber reinforced plastics has been subject to research for many years. Especially drilling with its resulting workpiece damage such as spalling or delamination still is critical. Approaches to reduce damage usually aim at reducing axial thrust forces and thus reduce the damage-causing effects. In this article two milling strategies for hole making with standard tools are presented, which actively direct process forces toward the center of the workpiece when machining the outer layers: a three-axial combined process of circular and spiral milling as well as a five-axial process called wobble milling. Better machining results are expected, as the material may act as its own back-up, thus reducing especially surface damages. Basic considerations and calculations regarding the direction of the theoretical process forces in dependence on the tool movement are given. Machining experiments have been performed on short glass fiber reinforced polyester and the resulting workpiece damage has been evaluated to assess the potential of the new strategies. Additionally some computer tomography scans have been obtained to qualitatively assess the machined surfaces. The experimental results support the presented idea: machining damage can be significantly reduced by machining strategies which direct the process forces inwards as compared to the reference process of circular milling. The results also indicate that the damage decreases with an increasing ratio of process forces which are directed toward the center of the workpiece.


[ 9 ] Schulze, V.; Becke, C. & Pabst, R. (2011), "Specific machining forces and resultant force vectors for machining of reinforced plastics", CIRP Annals - Manufacturing Technology, vol. 60, pp. 69-72.
Abstract:
When machining fiber reinforced plastics, the machining forces may induce workpiece damage if they exceed the workpiece is anisotropic strength values. Knowledge of the resultant force vectors is therefore important to allow optimization of tool geometry and machining strategy. This article deals with experimentally obtained machining forces on short glass fiber reinforced polyester. Specific cutting, passive and axial forces have been determined for varied parameters of cutting velocity, cutting depth, cutting edge rounding and tool inclination. Generic multivariate regression models have been calculated, which, implemented in a kinematic simulation, allow calculation of machining forces (and direction) for arbitrary milling operations.


[ 10 ] Schulze, V.; Weber, P. & Ruhs, C. (2012), "Increase of process reliability in the micro-machining processes EDM-milling and laser ablation using on-machine sensors", Journal of Materials Processing Technology, vol. 212, no. 3, pp. 625-632.
Abstract:
In micro production micro electric discharge machining (µEDM) and laser ablation are two established manufacturing methods. Due to the thermal material removal mechanism there are some challenges to provide the needed process reliability. In both cases it is important to ensure a precise manufacturing process by the correct positioning of the tool, e.g. the laser spot, relative to the work piece and the measurement and elimination of geometrical deviations. Using the EDM-milling process to manufacture small cavities a deviation of the manufactured depth and a waviness of the surface may appear if the compensation of the tool wear does not work correctly. A confocal white-light sensor can be used to measure the surface of the machined cavity after the EDM process. An on-machine system provides the possibility to rework the work piece without unclamping it. Combining these two procedures in an automatic working quality loop the accuracy of the manufactured depth can be improved down to a maximum deviation of less than 2 µm. Regarding the laser ablation process using ultra short pulsed Nd:YAG lasers problems arise if the focal plane is not on the surface of the work piece. Due to the manufacturing in layers occurring deviations in the surface remain until the end of the machining process. In this work an acoustical sensor is used to provide a correctly adjusted focal plane at the beginning of the first manufacturing step. Acoustic emissions are detected during the ablation process. A signal analysis of the airborne sound spectrum emitted by the process enables specific conclusions about the focal position of the laser beam. Based on this correlation an acoustic focus positioning is built up and tested on a ceramic work piece. The focal plane can then be adjusted automatically before the ablation.


[ 11 ] Helu, M.; Behmann, B.; Meier, H.; Dornfeld, D.; Lanza, G. & Schulze, V. (2012), "Impact of green machining strategies on achieved surface quality", CIRP Annals, pp. 55-58.
Abstract:
Green machining strategies can affect several aspects of a manufacturing system including part quality, which must remain sufficient to ensure the product's value. Improved part quality can also reduce life cycle environmental impacts through increased resource efficiency, which adds a further consideration. This paper quantifies the impact of these strategies on the achieved surface quality of turned titanium in the context of various resource costs including electrical energy, tool wear, and service costs. The results suggest that the final surface quality is most influenced by the finish cut(s) and feed rate. Part functionality is also an important consideration for resource efficiency.


[ 12 ] Lanza, G.; Fleischer, J.; Schulze, V.; Appel, D.; Behmann, B. & Bertsch, D. (2012), "Life Cycle Performance in der Produktionstechnik", wt Werkstattstechnik online, vol. 7, pp. 513-517.
Abstract:
Für produzierende Unternehmen an Hochlohnstandorten ist eine Kostenbetrachtung über Lebenszyklen entscheidend. Dies stellt sowohl Betreiber als auch Hersteller von Produktionsanlagen vor Herausforderungen. Am Institut für Produktionstechnik (wbk) des Karlsruher Instituts für Technologie (KIT) wurde der Forschungsschwerpunkt Life Cycle Performance (LCP) etabliert, welcher auf die Bewertung, Optimierung und Gestaltung von zuverlässigen und effizienten Systemen über den gesamten Lebenszyklus abzielt.


[ 13 ] Schulze, V.; Ambrosy, F. & Zanger, F. (2012), "Spanender Endbearbeitungsprozess zur Modifizierung der Randzonenzustände", Konstruktion - Zeitschrift für Produktentwicklung und Ingenieur-Werkstoffe, pp. 14-16.
Abstract:
Endbearbeitungsprozesse sind heute primär auf das Erreichen der in den Bauteilzeichnungen festgelegten Maße und Oberflächenrauheiten ausgerichtet. Die gezielte Fertigung von Randzonen, welche ein optimiertes tribologisches Verhalten im Betrieb ermöglichen, stellt bisher kein Optimierungsziel dar. Die Bildung dieser triboinduzierten Grenzschichten beginnt jedoch schon während der Fertigung. Der Endbearbeitungsprozess führt sowohl zu Änderungen der Topografie als auch zu Modifikationen der strukturellen Zusammensetzung des oberflächennahen Werkstoffvolumens. Bei optimierter Fertigung können so gezielt bereits im letzten Bearbeitungsschritt nanokristalline Randschichten erzeugt werden, welche das Reibungs- und Verschleißverhalten günstig beeinflussen.


[ 14 ] Kümmel, J.; Poser, K.; Zanger, F.; Michna, J. & Schulze, V. (2013), "Surface layer states of worn uncoated and TiN-coated WC/Co-cemented carbide cutting tools after dry plain turning of carbon steel", Advances in Tribology, pp. 1-10. http://dx.doi.org/10.1155/2013/519686
Abstract:
Analyzing wearmechanisms and developments of surface layers inWC/Co-cemented carbide cutting inserts is of great importance for metal-cutting manufacturing. By knowing relevant processes within the surface layers of cutting tools during machining the choice of machining parameters can be influenced to get less wear and high tool life of the cutting tool. Tool wear obviously influences tool life and surface integrity of the workpiece (residual stresses, surface quality, work hardening, etc.), so the choice of optimised process parameters is of great relevance. Vapour-deposited coatings onWC/Co-cemented carbide cutting inserts are known to improve machining performance and tool life, but the mechanisms behind these improvements are not fully understood. The interaction between commercial TiN-coated and uncoated WC/Co-cemented carbide cutting inserts and a normalised SAE 1045 steel workpiece was investigated during a dry plain turning operation with constant material removal under varied machining parameters. Tool wear was assessed by light-optical microscopy, scanning electron microscopy (SEM), and EDX analysis.The state of surface layer was investigated by metallographic sectioning. Microstructural changes and material transfer due to tribological processes in the cutting zone were examined by SEM and EDX analyses.


[ 15 ] Schulze, V.; Michna, J.; Zanger, F.; Faltin, C.; Maas, U. & Schneider, J. (2013), "Influence of cutting parameters, tool coatings and friction on the process heat in cutting processes and phase transformations in workpiece surface layers", HTM Journal of Heat Treatment and Materials, vol. 68, pp. 22-31.
Abstract:
The surface states and thus the functionality of machined workpieces are influenced by parameters of the process and the cutting tool. Depending on these variables different mechanical and thermal loads lead to changing characteristics of components. This paper presents a 2D-FE-cutting simulation model predicting machining induced phase transformations of workpiece surface layers for the steel 42CrMo4 (AISI 4140) considering detailed friction modeling between tool and workpiece, based on tribological experiments. The cutting simulation model was developed using the commercial software ABAQUS. Friction and phase transformations are implemented using specific user subroutines. The model calculates the process of austenization and the transformed volume fraction of the phases ferrite/perlite, bainite and martensite. Additional thermo dynamical simulations of the heat transfer using the code INSFLA are performed. The simulated temperatures, cutting forces and phase transformations are compared to orthogonal cutting experiments.


[ 16 ] Fleischer, J.; Schulze, V. & Kotschenreuther, J. (2009), "Extension of cutting force formulae for microcutting", CIRP Journal of Manufacturing Science and Technology, pp. 75-80.
Abstract:
During scaling of cutting processes size-effects occur due to not similarly scalable input parameters, e.g. ratio of cutting edge radius to depth of cut. These effects not foreseen by conventional similarity mechanics result in altered behaviour regarding cutting forces, sensitivity for various parameters, chip formation, surface texture and surface layer. This paper identifies effects associatedwith the transition frommacro to microcutting by means of a turning process. Different available models for macroprocesses have been analysed and one has been extended by a term for the cutting edge radius. This results in a significantly better prediction of the acting forces and an enhanced understanding of the process.


[ 17 ] Cuba Ramos, A.; Autenrieth, H.; Strauß, T.; Deuchert, M.; Hoffmeister, J. & Schulze, V. (2012), "Characterization of the transition from ploughing to cutting in micro machiningand evaluation of the minimum thickness of cut", Journal of Materials Processing Technology, vol. 212, pp. 594-600.
Abstract:
When the machining process is miniaturized two process mechanisms, ploughing and chip formation, are essential and a critical cutting thickness needs to be exceeded so that not only ploughing will occur but chips will also be formed. The ploughing effect thereby influences the chip formation process, workpiece surface roughness, burr formation and residual stress state after processing and is therefore of great interest. In order to optimize the machining process a better understanding of the minimum thickness of cut is crucial. The changes in surface topography along the cutting track occurring during machining with a constant feed rate of the cutting tool were analyzed. The influence of the built-up edge phenomena on the micro machining process was investigated for normalized AISI 1045 using confocal white light microscopy and scanning electron microscopy. Furthermore the sin2 -method was applied in order to study the residual stress state in the workpiece surface induced by the machining process. Both surface layer properties investigated, surface roughness and residual stresses, show a characteristic transition indicating a Change in the dominating process mechanisms. Based on these results a model is developed to determine the minimum thickness of cut. The Minimum thickness of cut is found to significantly decrease with higher cutting velocities and to moderately increase with higher cutting edge radii. In addition a propagation of error for the values obtained with the model was performed, proving the quality of the model developed.


[ 18 ] Ambrosy, F.; Zanger, F. & Schulze, V. (2015), "FEM-simulation of machining induced nanocrystalline surface layers in steel surfaces prepared for tribological applications ", CIRP Annals - Manufacturing Technology, vol. 64, no. 1, pp. 69-72. http://dx.doi.org/10.1016/j.cirp.2015.04.063
Abstract:
A formation of nanocrystalline grains due to dynamic recrystallization within the workpiece surface layer (AISI4140) resulting from machining has proven to be suitable for obtaining improved tribological and fatigue behaviour. In the work presented an optimization of the machining process is carried out with cutting simulations using a continuous remeshing method and describing surface layer generation. The simulations describe the influence of process parameters and tool geometry on evolution of grain size distributions within the subsurface and affected depth after this thermo-mechanical processing. The validation is performed by experimental analyses based on cutting technology and focused ion beam technique.


[ 19 ] Matuschka, B.; Granser, T.; Rohde, M.; Schulze, V. & Seifert, H. (2015), "Alternative Herstellung von elektrischen Leitern in der Mikrotechnik", wt Werkstattstechnik online, vol. 11, pp. 800-804.
Abstract:
Dieser Fachartikel beschäftigt sich mit der Aufbringung von elektrischen Leiterbahnen aus Aktivlot auf Keramikkörper. In Versuchen konnte eine Befüllung von Kavitäten in Oxidkeramikkörpern mit Aktivlot erzielt werden. Anschließend wurde der Zusammenhang des Volumenanteils der Legierungskomponenten mit dem spez. Widerstand untersucht. Dies bietet die Grundlage für weitere Untersuchungen, den elektrischen Widerstand des Lots für die Anwendung als Leiterbahnmaterial zu optimieren.


[ 20 ] Schulze, V.; Meier, H.; Strauß, T. & Gibmeier, J. (2012), "High Speed Broaching of Case Hardening Steel SAE 5120", Procedia CIRP 1, pp. 431-436.
Abstract:
To achieve knowledge of the effects of broaching to the component and the influence to subsequent process steps, broaching experiments have been carried out on case hardening steel SAE 5120 using different tools and cutting speeds up to 50 m/min with use of cooling lubricant and in dry machining. The process forces were analyzed and the resulting surface was examined using Xray diffraction and roughness testers. High cutting speeds lead to low cutting forces but high residual stresses. An influence of the varied parameters and machining conditions to the surface quality was not detected.


[ 21 ] Schulze, V.; Zanger, F. & Ambrosy, F. (2013), "Quantitative Microstructural Analysis of Nanocrystalline Surface Layer Induced by a Modified Cutting Process", Advanced Materials Research, vol. 769, pp. 109-115. 10.4028/www.scientific.net/AMR.769.109
Abstract:
Present work analyzes the influence of process and modified geometry parameters of an orthogonal final machining process (finishing) on the nanocrystalline surface layers generation by quantitative microstructural analysis. Thereby, AISI 4140 (German Steel 42CrMo4) in a state quenched and tempered at 450°C is used as workpiece material. Metallic materials used in technical applications are polycrystalline in nature and are composed of a large number of grains which are separated by grain boundaries. The grain size has a strong influence on the mechanical material properties. Metallic parts with a severe nanocrystalline grain refinement in the near-surface area show many beneficial properties. Such surface layers considerably influence the friction and wear characteristics of the workpiece in a subsequent usage as design elements working under tribological loads due to their extreme superplastic properties. The tribologically induced surface layers formation already starts during the manufacturing of the components, by leading to a change of workpiece material near the surface. Particularly when the depth of cut h becomes of the same order as the cutting edge radius rß, the ploughing process becomes increasingly important and strongly influences the chip formation process. The plastic zone depth within the surface layer is especially influenced by the design of the microgeometry of the cutting tools and increases almost linearly with the ratio of cutting edge radius rß to depth of cut h. The plastic zone is hereby approximately of the same order of magnitude as the cutting edge radius rß. Parameters that are studied and taken into account in the manufacturing process are cutting edge radius rß, depth of cut h and cutting velocity vc. Variations of cutting depth h are performed in a range of 30 to 100 µm and variations of cutting edge radius rß are executed in a range of 30 to 150 µm. The microgeometries of the tools are preconditioned by abrasive grinding with a drag finishing machine and observed by a confocal light microscope. A cutting velocity vc of 25 and 150 m/min is applied. The evaluation of the manufacturing process is carried out by detailed analyses of the microstructural conditions in the surface layer after processing using a Focused Ion Beam system. These material characterizations provide information about the surface engineering concerning the microstructural changes in the workpiece surface layer due to machining. Hereby, the grain size analysis is investigated by a line method based on the characterization of portions of several test-lines positioned across the two dimensional Focused Ion Beam images.


[ 22 ] Schulze, V. (2014), "Modeling of Face Milling", CIRP Encyclopedia of Production Engineering, pp. 1-9. 10.1007/SpringerReference_357950

[ 23 ] Schulze, V.; Zanger, F. & Hoppen, P. (2014), "Broaching", CIRP Encyclopedia of Production Engineering, pp. 1-12.

[ 24 ] Klotz, S.; Zanger, F. & Schulze, V. (2014), "Influence of Clamping Systems during Milling of Carbon Fiber Reinforced Composites ", Procedia CIRP, pp. 38-43. http://dx.doi.org/10.1016/j.procir.2014.07.142
Abstract:
Carbon fiber reinforced composites (CFRP) are mostly manufactured near net shape. Nevertheless, a final milling step at the edges of the cured components is still necessary. Damages which occur during milling or drilling of CFRP lower the durability of the components and increase the production costs. Requirements concerning the clamping system for milling or drilling CFRP are rising simultaneously with increasing complexity of the components. This stresses the need for complex clamping systems like linear clamping jaws around the whole workpiece. However such types of clamping systems induce poor accessibility to the component being worked on and hence longer machining time. As a result to the need for complex clamping systems, the production costs are increased. Therefore, several benefits can be achieved by increasing the distances between the clamping points of the clamping system to reduce machining time and production costs. This paper discusses investigations of milling tests with variable clamping conditions of the workpieces. In the experiments a linear milling operation the edge of the workpiece is examined. The clamping of the planar specimens was realized with a clamping system which enables the adjustment of different distances between the clamping points of the specimen. The process forces and the resulting damage at the workpiece surfaces were measured during the experiments. These results are compared with a linear clamping system to examine the influence of rising clamping distances. The results demonstrate that the distance of the clamping points while milling the edge of the workpiece has a significant influence on the process forces.


Peer-reviewed papers at conferences

[ 1 ] Weule, H.; Vöhringer, O.; Schulze, V.; Biesinger, F. & Söhner, J. (2000), "Zerspankraftmessung und Randschichtcharakterisierung beim Hochgeschwindigkeits-Stirnplanfraesen". Kolloquium des DFG-Schwerpunktprogramms "Spanen metallischer Werkstoffe mit hohen Geschwindigkeiten", eds. Tönshoff, H., pp. 129-151.

[ 2 ] Weule, H.; Söhner, J.; Biesinger, F.; Schulze, V. & Vohringer, O. (2001), "Examinations and 3D-Simulations of HSC face milling process". Proceedings of the 4th CIRP International Workshop on Modeling of Machining Operations, pp. 1147-1150.

[ 3 ] Biesinger, F.; Söhner, J.; Schulze, V.; Vöhringer, O. & Weule, H. (2001), "Aspects of material science and production engineering of the high-speed-cutting process and their finite-element simulation". Metal Cutting and High Speed Machining, eds. D. Dudzinski, H. S., pp. 67-71.

[ 4 ] Fleischer, J.; Schmidt, J.; Kotschenreuther, J.; Löhe, D.; Schulze, V. & Gumbsch, P. (2003), "Modelling, simulation and experimental tests for process scaling of cutting processes with geometrically defined edge". Tagungsband Process Scaling, eds. Vollertsen, F. & Hollmann, F., pp. 121-136.

[ 5 ] Kotschenreuther, J.; Delonnoy, L.; Hochrainer, T.; Schmidt, J.; Fleischer, J. & Schulze, V. (2004), "lnfluences of Process Scaling in Metal Cutting with Geometrically Defined Cutting Edges". Proceedings of 4th euspen International Conference, eds. Euspen, pp. 173-174.
Abstract:
A main tendency in technology is the miniaturization of devices and components. Micro-cutting has the potential to overcome restrictions other operations are limited to. When the cutting-depth decreases to the order of micro-meters some unexpected phenomena appear. These phenomena, not foreseen by conventional scaling used for dimensioning in cutting, are called size-effects.


[ 6 ] Fleischer, J.; Kotschenreuther, J.; Löhe, D.; Gumbsch, P.; Schulze, V. & Delonnoy, L. (2005), "An integrated approach to the modeling of size-effects in machining with geometrically defined cutting edges". CIRP Workshop, pp. 123-129.
Abstract:
In order to comprehensively investigate size-effects occurring in the miniaturization of cutting processes, material science, simulation and experimental testing are combined. Similarity mechanics are used to guide the parameter variation in two-dimensional finite-element simulations for orthogonal cutting using ABAQUS/Explicit. The ratedependent material model used, leads to size-effects like an increase of the specific cutting force while reducing the depth of cut. The influence of rounded cutting-edges on the chipping process and the characteristics of the generated surface were investigated in 2D-simulations. Rounded cutting tools are shown to produce severe plastic deformations of the generated surface and deep plastically deformed surface layers.


[ 7 ] Fleischer, J.; Kotschenreuther, J.; Autenrieth, H.; Schulze, V.; Löhe, D. & Weber, M. (2007), "Influence of Multiple Machining Steps on the Specific Cutting Force and Surface Characteristics in Micro Cutting ". Proceedings of the 2nd International Conference on New Forming Technology, pp. 551-561.

[ 8 ] Fleischer, J.; Schulze, V.; Deuchert, M.; Autenrieth, H.; Löhe, D. & Weber, A. (2008), "Influence of process parameters on the specific reaction forces and surface characteristics in orthogonal micro-cutting". Conference Proceedings 3rd International Conference on CIRP High Performance Cutting, pp. 675-685.
Abstract:
Nonlinear scaling effects for decreasing cutting depths h , so called processspecific size-effects, are investigated for normalized AISI 1045 in an orthogonal cuttingprocess. The characteristic increase of the specific cutting force c k for decreasingcutting depths is described by the Victor-Kienzle-Equation. Particularly for microcutting - when the cutting depth becomes of the same order as the cutting edgeradius â r - the ploughing process becomes increasingly important and influences thechip formation process strongly. Therefore, the Victor-Kienzle-Equation is extended bya term taking the influence of the ratio r / h â on the specific cutting forces intoconsideration. Furthermore a formulation for the dependence of the specific passiveforce p k on r / h â is given analogously to the specific cutting force. Similar to thereaction forces, the surface characteristics - namely surface work-hardening androughness - are also influenced by â r and were therefore measured in detail.


[ 9 ] Schulze, V.; Pabst, R. & Michna, J. (2008), "Modeling the Heat Flux as an Input Parameter to Simulate Cutting Processes". Proceedings on 11th CIRP Conference on Modeling Operations, eds. Jarred C. Heigel, R. W. I., pp. 155-162.
Abstract:
The process of dry machining is facing enormous challenges as the heat input isconsiderable due to the lack of coolant. The heat input results in an inhomogeneouslydistributed temperature which leads to an omni-directional expansion. This distortion canbe calculated using FEM simulation. However, it requires a detailed knowledge of theheat flux as an input parameter in order to simulate each operation. To date, this canonly be determined through extensive experiments. This paper aims at presenting thecurrent findings in regards to the generation of a mathematical model describing theheat input during a milling process as a function of cutting parameters and toolgeometry. Based on this model, the heat flux as an input parameter can be calculated.This allows for the simulation and optimization of machining sequences.


[ 10 ] Schulze, V.; Weber, P. & Haupt, S. (2008), "Hybrid machine tool based on the combination of laser ablation and electrical discharge machining (EDM)".
Abstract:
Both laser ablation and electrical discharge machining (EDM) enable a material removal without any process forces and thus can ablate materials which are hard to machine by conventional processes. By laser ablation with ultra short laser pulses smallest structures can be realized with good surface qualities. EDM on the other hand reaches higher aspect ratios and ablation rates at a certain diameter range. A hybrid machine tool was developed, which combines the two processes. By this combination the advantages of both processes can be utilized for the flexible and precise manufacturing of micro parts with structure sizes down to 10 microns. This new concept enables an effective and economic manufacturing of micro structures. A possible field of application is the manufacturing of mold Inputs for micro injection molding.


[ 11 ] Schulze, V. & Rilli, R. (2008), "Werkzeugauslegung und Prozesskenngrößen für das Trockenräumen". Pp. 2.

[ 12 ] Schulze, V. & Kühlewein, C. (2009), "Wälzschälen". Eds. FVA, pp. 39-50.

[ 13 ] Schulze, V.; Michna, J. & Pabst, R. (2009), "Modeling Of The Heat Input For The Face-Milling Of EN-GJL-250". Eds. CIRP / MU. Mondragon Unibertsitateko Zerbitzu Editoriala, pp. 243-248.
Abstract:
Due to absence of coolant in dry machining, the heat input during the cutting process increases and, as a result, an inhomogeneous temperature distribution in the work piece can be observed. This can cause work piece displacements which can lead to problems in reaching critical tolerances. FEM simulations can be used to calculate and handle these work piece displacements. Input data is required for such a FEM simulation, which could be gained from mathematical models based on experimental data. This paper presents a mathematical model developed for the face-milling of the material EN-GJL-250, including only different tool geometries, cutting edges and rake angles. This research project aims to develop an integrated model for the milling of EN-GJL-250, including all dominating parameters affecting the heat input into the work piece. The model serves as a means to simulate and handle displacements.


[ 14 ] Schulze, V.; Kühlewein, C. & Rilli, R. (2009), "Neue Ansätze zur Weichbearbeitung von Innenverzahnungen - Wälzschälen und Räumen". Eds. Prof. Dr.-Ing. K. Felten, pp. 99-120.
Abstract:
Wälzschälen ist ein kontinuierliches spanabhebendes Verfahren zur Herstellung von Zahnrädern und rotationssymmetrischen Bauteilen mit periodischen Strukturen. Das Einsatzspektrum umfasst in der Weichbearbeitung sowohl wälzfräsbare Verzahnungen als auch Teilbereiche des Wälzstoßens und ist auch für die Hartfeinbearbeitung von Verzahnungen geeignet. Das Verfahren wurde Anfang des 20. Jahrhunderts entwickelt und patentiert, eine anhaltende Etablierung am Markt konnte bisher nicht erreicht werden, obwohl das Wälzschälen der Forderung nach hoher Produktivität vereint mit hoher Flexibilität gerecht werden kann. Fortschritte im Bereich der Schneidstoffe, Beschichtung, Maschinen- und Steuerungstechnik sowie der computergestützten Simulationstechnik haben das Verfahren in den letzten Jahren wieder aufleben lassen und deutliche Fortschritte auf dem Weg zum industriellen Einsatz ermöglicht. Da das Wälzschälen hier in direkter Konkurrenz zu den etablierten Verzahnverfahren Wälzfräsen und Wälzstoßen steht, sind die Anforderungen dementsprechend hoch. In den vergangenen Jahren wurden am Institut für Produktionstechnik (wbk) der Universität Karlsruhe (TH) umfangreiche Untersuchungen zum Wälzschälverfahren durchgeführt. Auf der Basis einer Standard-Vertikaldrehmaschine steht eine Versuchsmaschine für das Wälzschälverfahren bereit, bei der eine Wälzschäleinheit in den Arbeitsraum implementiert wurde. Bei den Untersuchungen lag der Fokus bisher hauptsächlich in der Weichbearbeitung und zunächst insbesondere bei der Herstellung von Aussenverzahnungen. Bei der Herstellung von Ritzeln aus dem Werkstoff 16MnCr5S mit einem Außendurchmesser von ca. 50 mm und einem Modul von 1,75 mm bei 23 Zähnen konnte das Potential des Verfahrens hinsichtlich der Produktivität und der erreichbaren Verzahnungsqualität demonstriert werden. Weiteres Potential zeigt das Wälzschälen auch bei der Herstellung von Innenverzahnungen. So beziehen sich die derzeitigen Untersuchungen insbesondere auf das Innenschälen und, neben der Verfahrensentwicklung, auf die hier zusätzlichen technologischen Herausforderungen, wie das zuverlässige Herausspülen von abgeschälten Spänen. Im Gegensatz zum Wälzschälen ist Räumen kein Verfahren, das ausschließlich zur Herstellung von Zahnrädern Verwendung findet. Es ist vielmehr ein Verfahren, das außerhalb der Verzahntechnik breite Anwendung findet und in bestimmten Bereichen der Zahnradherstellung angewendet wird. Das Spanen erfolgt beim Räumen mit einem mehrschneidigen Werkzeug, dessen Schneiden hintereinander jeweils um die Spanungsdicke gestaffelt angeordnet sind. Bei der Bearbeitung eines Bauteils kommt jede Schneide nur einmal in Eingriff. Geräumte Bauteile weisen hohe Oberflächengüten und Genauigkeiten auf. Toleranzen zwischen IT6 und IT8 sind erreichbar. Durch umfassende Untersuchungen zum Räumen ohne Kühlschmierstoff konnte gezeigt werden, dass trockene Räumprozesse möglich sind und gute Qualitäten der bearbeiteten Bauteile erzielt werden können. Auch konnte der Verschleiß der Werkzeuge auf das Niveau der gekühlten Prozesse bzw. darüber hinaus reduziert werden. Mit der richtigen Wahl der Werkzeug- und Prozessparameter können stabile Räumprozesse ohne Kühlschmierstoff eingerichtet werden.


[ 15 ] Kienzler, A.; Deuchert, M. & Schulze, V. (2009), "Burr Minimization and Removal by Micro Milling Strategies or Micro Peening Processes". Proceedings of the CIRP International Conference on Burrs-Analysis Control and Removal, eds. CIRP, pp. 237-243.
Abstract:
Micro milled mold inserts made from hardened and tempered steel can have burrs in the size order of 50 ìm at the edges. These burrs often prevent the easy demolding of green bodies from micro powder injection molds. Further surface treatments on the molds are necessary to improve surface quality thus facilitating demolding processes. In the present study, three different processes: micro milling, abrasive micro peening and ultrasonic wet peening, have been investigated for their suitability as viable solutions for reducing or eliminating burrs. The tool used for the micro milling process is capable of removing existing burrs but creates new burrs which are inherent to the tool movement over the machined surface. While abrasive micro peening leads to a reduction of burrs on the mold surface, the material below the impacted surface is plastically deformed. Ultrasonic wet peening showed the best effectiveness at removal of burrs of a wide variety of complex geometries in a short processing time and without plastic deformation of the edge zones.


[ 16 ] Schulze, V.; Weber, P. & Ruhs, C. (2009), "Implementation of on-machine measurements using confocal white-light sensors for micro Electrical Discharge Machining and micro laser ablation". Pp. 179-182.
Abstract:
In micro system technology there is still a huge demand for smaller and more filigree components. Furthermore manufacturers of micro parts are challenged to deal with the high quality standards of their customers. Therefore measurement devices become more and more important. This manuscript deals with specific applications for a confocal white-light sensor integrated in a micro laser ablation (µLBM) machine - and a micro electrical discharge machining (µEDM) machine. In µLBM one sensible parameter is the focus position while machining. Therefore the planarity of the work piece must be guaranteed anytime. This can be achieved by an on-machine measuring device. Another advantage of an integrated sensor is the control of the actual depth of a manufactured structure. This is a challenge in µLBM because of the non constant ablation volume from layer to layer. It is also a challenge in µEDM because of the tool wear which is characteristic for this manufacturing process. By using a confocal white-light sensor the depth of a cavity and the surface roughness can be detected without unclamping the work piece. An updated path planning can be done afterwards without inaccuracies caused by reclamping the work piece.


[ 17 ] Schulze, V.; Deuchert, M.; Kienzler, A.; Ruhs, C. & Weber, P. (2009), "Prozessübergreifende Betrachtung abtragender Verfahren zur Mikroformeinsatzherstellung". Eds. F. Vollertsen, BIAS-Verlag, pp. 125-131.
Abstract:
Beim Mikrofräsen, der Mikrofunkenerosion (µEDM) und der Mikrolaserablation (µLBM) handelt es sich um geeignete Verfahren für die Mikrostrukturierung von Formeinsätzen. Dabei weist jedes dieser Verfahren spezifische Eigenschaften auf, die es für gewisse Fertigungsaufgaben prädestinieren. Weiterhin bietet das Mikroabrasivstrahlen die Möglichkeit einer Nachbehandlung der Formeinsätze, um unerwünschte Randschichteigenschaften des Fertigungsprozesses zu mindern oder gar zu beseitigen. Im Folgenden wird ein Einblick in die Forschungstätigkeiten bezüglich der Fertigungsverfahren zur Formeinsatzherstellung gegeben. Darüber hinaus wird dargelegt, welche Möglichkeiten eine Nachbehandlung mittels Abrasivstrahlen bietet. Abschließend wird aufgezeigt, wie erarbeitetes Wissen anhand eines Mikrostrukturkataloges nachhaltig sichergestellt und zugänglich gemacht wird.


[ 18 ] Fleischer, J.; Schulze, V.; Burtscher, J. & Dosch, S. (2014), "Robot-based guiding of extrusion profiles - Increase of guiding accuracy by considering the temperature-dependent effects". Procedia CIRP, Proceedings of the International Conference on Manufacturing of Lightweight Components - ManuLight 2014, eds. Elsevier, Elsevier, pp. 21-26.
Abstract:
Three-dimensionally curved extrusion profiles are used to manufacture lightweight frame structures. These profiles have to be flexibly manufactured, especially for a small batch production. For this reason, a flexible process chain with an automated Extrusion process was build up. In this paper an approach for offline calculation of path data for the guiding of unsteady extrusion profiles with industrial robots is presented. This approach includes a consideration of the profile deformation caused by cooling during production. The required correction values are determined by using a coupled kinematic and thermal FEM simulation.


[ 19 ] Meier, H.; Pabst, R. & Schulze, V. (2009), "Process chains in production". Eds. Lehrstuhl für Technische Mechanik (LTM) Universität Paderborn, pp. 18.
Abstract:
The increase of product quality at reduced production times and minimized costs can nowadays not only be realized by optimizing single manufacturing processes but by the holistic examination of the process chain. Research Area B examines the process chain of an solid component, represented by a shift collar which is used in automotive gearings. Project part B1 is aimed to optimize process management of the process steps during soft and hard broaching. The shift collars geometry is at first simplified from the original tooth structure and demonstrated by an off-site broaching process. Afterwards the verifications will be created on a realistic geometry with the intended inner broaching process on the rotary symmetric shift collar. The necessary process parameters will be determined experimentally and through a parameter variation a wide data base is created to develop a simulation model. The component´s conditions are being analyzed after the broaching process concerning residual stresses and dimensional change (distortion) and are applied with cutting forces and tool changes (i.e. wear) to the simulation model.


[ 20 ] Schulze, V. & Weber, P. (2010), "Precise ablation milling with ultra short pulsed Nd:YAG lasers by optical and acoustical process control". Proceedings of SPIE Voll 7585, eds. Wilhelm Pfleging, W. H., pp. 1-9.
Abstract:
Laser ablation milling with ultra short pulsed Nd:YAG lasers enables micro structuring in nearly all kinds of solid materials like metals, ceramics and polymers. A precise machining result with high surface quality requires a defined ablation process. Problems arise through the scatter in the resulting ablation depth of the laser beam machining process where material is removed in layers. Since the ablated volume may change due to varying absorption properties in single layers and inhomogeneities in the material, the focal plane might deviate from the surface of the work piece when the next layer is machined. Thus the focal plane has to be adjusted after each layer. A newly developed optical and acoustical process control enables an in-process adjustment of the focal plane that leads to defined process conditions and thus to better ablation results. The optical process control is realized by assistance of a confocal white light sensor. It enables an automated work piece orientation before machining and an inline ablation depth monitoring. The optical device can be integrated for an online or offline process control. Both variants will be presented and discussed. A further approach for adjustment of the focal plane is the acoustical process control. Acoustic emissions are detected while laser beam machining. A signal analysis of the airborne sound spectrum emitted by the process enables conclusions about the focal position of the laser beam. Based on this correlation an acoustic focus positioning is built up. The focal plane can then be adjusted automatically before ablation.


[ 21 ] Meier, H.; Rilli, R. & Schulze, V. (2010), "Nass- und Trockenräumen von 16MnCr5". Eds. Dr.-Ing. Rüdiger Pabst, Shaker Verlag, pp. 39-43.
Abstract:
Qualitätssteigerungen, einhergehend mit reduzierten Fertigungszeiten und Kosteneinsparungen gelingen heutzutage nicht mehr allein durch Optimierung einzelner Prozesse. Vielmehr muss die gesamte Prozesskette im Herstellungsprozess betrachtet werden. Um jedoch die Prozesskette als Ganzes optimieren zu können, ist es zunächst nötig, die einzelnen Prozessschritte eingehend zu untersuchen und die Wechselwirkungen auf den jeweils nachfolgenden Schritt herauszustellen. Die Eigenschaften geräumter Werkstücke werden, neben dem gewählten Werkstoff, signifikant von den Prozessparametern und der Verschleißentwicklung des Werkzeuges beeinflusst. Die hier vorgestellten Ergebnisse zeigen die auftretenden Bearbeitungskräfte und Verschleißzustände bei der Räumbearbeitung von 16MnCr5. Es konnte gezeigt werden, dass neben der industriell angewandten Bearbeitung mit Kühlschmierstoffen ein Räumen im Trockenschnitt mit verbesserten Oberflächengüten und geringerem Werkzeugverschleiß möglich ist. Dies schafft die Grundlage, geeignete Bearbeitungsstrategien für das zu bearbeitende Bauteil zu schaffen und weiterführend auf seine Randschichteigenschaften zu untersuchen. Somit kann das Prozessverständnis bei Räumen von Einsatzstählen, auch unter Berücksichtigung wirtschaftlicher Gesichtspunkte, weiter ausgebaut und die Optimierung der gesamten Prozessketten weiter vorangetrieben werden. Prozessketten, Räumen, Einsatzstähle


[ 22 ] Osterried, J.; Zanger, F. & Schulze, V. (2009), "chip formation simulations in hard machining". 22. Workshop Composite Forschung der Mechanik / 3. Forum Metallplastizität, eds. Mahnken, R.; Böhlke, T.; Wünsch, O.; Nestler, B. & Schulze, V., pp. 19.
Abstract:
Broaching of hardened steels is one of the sub-processes of the process-chain examined in Graduate School 1483. This topic aims at predicting the surface layer conditions, like residual stresses and distortion, after hard machining within the process chain. A hard machining strategy with minimal machining effort will be developed consequential for best possible surface layer and component conditions. Therefore the broaching of hardened materials is mapped to simulation, based on the component characteristics resulting from preceding heat treatment. In doing so, the component is machining history is taken into account when simulating broaching within the process chain. Based on a global view of the component at heat treatment, it is crucial to transfer quantities specifying component state to a local mesh for chip forming simulations. Input data from heat treatment simulation have to be implemented to describe the actual component condition before hard machining. This condition has then to be set as an accurately defined initial state for the hard machining simulation. Defining the initial state is of great importance for simulations within the process chain, as the sub-processes are linked by inheriting the respective component conditions like residual stress behaviour. Therefore appropriate techniques have to be provided. For the development of the machining strategy, simulations with varied process parameters can be triggered consequently. At the end of the hard machining simulation process the present output quantities have to be translated into a global mesh of the three-dimensional component.


[ 23 ] Osterried, J.; Zanger, F.; Autenrieth, H. & Schulze, V. (2010), "Neue Simulationsmethode zur Randschichtcharakterisierung unter Berücksichtigung der Mehrfachspanbildung beim Räumen". Graduiertenkolleg 1483 Prozessketten in der Fertigung: Wechselwirkung, Modellbildung und Bewertung von Prozesszonen, Begleitband zur 1. Jährlichen Klausurtagung 2010, eds. Pabst, R.; Nestler, B. & Schulze, V., Shaker Verlag, pp. 57-61.
Abstract:
Um eine durchgängige Simulation einer Prozesskette, bestehend aus den Teilprozessen Weichbearbeitung, Wärmebehandlung, Hartbearbeitung und Oberflächenbehandlung, zu erreichen, müssen zunächst diese Teilschritte abgebildet und anschließend über geeignete Schnittstellen verkettet werden. Dadurch ist eine skalenübergreifende Betrachtung von lokaler Ebene im Einzelprozess bis zum globalen Bauteilzustand möglich. Das Bauteil innerhalb der fertigungstechnischen Prozesskette weist eine spezifische Bearbeitungsgeschichte auf. Diese vorliegenden Bauteilzustände müssen, als Voraussetzung zur Verkettung, zwischen den Teilprozessen übertragen werden können. Es wird eine Methode vorgestellt, um einem FE-Modell einen definierten Bauteilzustand als Anfangszustand vorzugeben. Das Aufprägen von Bauteilzuständen ermöglicht damit die Berücksichtigung der Bearbeitungsgeschichte und zudem die Durchführung von Mehrfachspansimulationen zur Abbildung des in der Prozesskette eingesetzten Räumverfahrens. Dazu werden die Zustände aus dem Nachlaufbereich der Schneide extrahiert und der Simulation des nächsten Zahnes unter Verwendung von Benutzerroutinen aufgeprägt. Die Spanbildungssimulation ist mittels Neuvernetzung realisiert.


[ 24 ] Zanger, F.; Autenrieth, H.; Hoffmeister, J. & Schulze, V. (2010), "Numerische Materialmodellierung und deren Anwendung in der virtuellen Produktion". Graduiertenkolleg 1483 Prozessketten in der Fertigung: Wechselwirkung, Modellbildung und Bewertung von Prozesszonen, Begleitband zur 1. Jährlichen Klausurtagung 2010, eds. Pabst, R.; Nestler, B. & Schulze, V., Shaker Verlag, pp. 125-129.
Abstract:
Eine realitätsnahe Beschreibung von Fertigungsprozessen mit hohen Umformgraden setzt eine Berücksichtigung des Materialversagens im Werkstück voraus. Das Versagensverhalten zeigt eine Abhängigkeit von den Zustandsgrößen Spannungszustand, Verformungsgeschwindigkeit und Temperatur, die mittels analytischer Funktionen beschrieben werden können. Des Weiteren ist das Versagensverhalten werkstoffspezifisch. Eine realistische Materialmodellierung ermöglicht die simulative Abbildung unterschiedlichster Fertigungsprozesse, sodass stabile Prozessparameter identifiziert werden können. Die hier vorgestellten Materialmodelle für die beiden Werkstoffe C45E und Ti-6Al-4V, in denen das elastisch-viskoplastische Verformungs- und das duktile Versagensverhalten berücksichtigt wurden, konnten erfolgreich unter anderem zur Beschreibung dynamisch belasteter Scherproben eingesetzt werden (C45E). Zudem wurden diese Modelle zur Beschreibung von Spanbildungsprozessen (C45E und Ti-6Al-4V) und eines Umformprozesses eingesetzt (C45E). Die entwickelten Modelle erlaubten eine Beschreibung der Spanformen, der Prozesskräfte und Temperaturen in den Scherzonen. Diese zeigten eine gute Übereinstimmung mit den experimentellen Befunden.


[ 25 ] Schulze, V. & Ruhs, C. (2010), "On-machine measurement for the micro-EDM-milling process using a confocal white-light sensor". Proceedings of the euspen International Conference , pp. 37-40.
Abstract:
This paper deals with the integration of an on-machine measurement device and its application during the micro-EDM-milling process. By using a confocal white-light sensor with a resolution of 25 nm directly on the EDM-machine the depth of a cavity can be detected without unclamping the work piece. This helps to avoid inaccuracies caused by reclamping the work piece between the manufacturing, the measurement and the reconditioning process. Due to the high resolution of the confocal white-light sensor it is also possible to measure the surface roughness on the ground of the cavity. This feature also provides the characterisation of the surface quality after the EDM-process.


[ 26 ] Schulze, V. & Kühlewein, C. (2010), "Process Development of the Skiving Technology". Pp. 1417-1419.
Abstract:
The progress in gearing has been stagnating lately due to an advanced development level and due to the fact that hereby the physical limits of the established manufacturing methods are almost met. Enhancing the performance means a great effort with only moderate success. Achieving progress in the reduction of manufacturing time, overall output of the process and endurance of the tools have become increasingly challenging. As an alternative of the common cutting methods such a gear hobbing, shaping and broaching, skiving is expected to be the key to higher performance of cutting. Skiving has a huge potential due to the fact that the method has not been developed further since the 1970s. Skiving in general is a continuous metal removing process for the machining of gears and rotational parts with periodical structures. The operational spectrum includes in the field of soft machining either generated and sub-ranges of shaped and broached gearings and is generally suitable for hard machining. Skiving offers both the advantages of high productivity and universal application for machining inside and outside periodic structures. Since the patent was assigned in the beginning of the 20th century the skiving manufacturing process retards at its physical limitation. So far skiving has only found a few applications, such as hard machining of external toothing. Until now, a sustainable establishment of the process in practice failed. Improvements in the development of cutting materials, coatings, simulation tools and, in particular in the technology of machine tools due to the implantation of directly driven electronic spindles, allow skiving to be suitable for a serial application. Applying skiving in soft machining universally for different geometries makes a holistic approach necessary.


[ 27 ] Schulze, V.; Zanger, F. & Klotz, S. (2013), "Verschleißbedingte Parameteranpassung bei der Bohrungsherstellung in faserverstärkten Kunststoffen". Verbundwerkstoffe, eds. Wanner, A. & Weidenmann, K. A., pp. 658-664.
Abstract:
Faserverstärkte Kunststoffe besitzen entlang der Faserrichtung hohe spezifische Festigkeiten und Steifigkeiten. Trotz deren meist endkonturnaher Herstellung müssen teilweise noch Bohrungen in die Bauteile eingebracht werden. Bei der Bohrbearbeitung entstehen Bearbeitungskräfte, die senkrecht zur Verstärkungsrichtung der Fasern wirken. Diese Prozesskräfte verursachen an den Decklagen Schädigungen in Form von Ausfransungen und Delaminationen. In den meisten Fällen werden die Bohrungen mit über die gesamte Werkzeugstandzeit gleichbleibenden Prozessparametern eingebracht. Bestehende Ansätze zur Vermeidung der Bauteilschädigungen zielen lediglich auf eine Reduzierung der Vorschubgeschwindigkeiten im Bereich des Bohrungsaustritts ab, um dort die kritischen Prozesskräfte zu verringern. Bei der Bohrbearbeitung mit konstanten Parametern verändern sich in Abhängigkeit des Verschleißzustands des Bohrwerkzeugs die Eingriffsverhältnisse der Werkzeugschneide, was in sich verändernden Prozesskraftrichtungen und zunehmenden Werkstückschädigungen resultiert. Eine andere Möglichkeit, die Schädigungen an den Bauteilen zu verringern, besteht daher in der dynamischen Anpassung der Prozessparameter an den aktuellen Verschleißzustand des Werkzeugs. Damit können durch die Einstellung von konstanten Eingriffsverhältnissen zwischen Werkzeugverschleiß und Schnitttiefe über die gesamte Werkzeuglebensdauer die Schädigungen an den Decklagen gezielt verringert werden. Es werden die Ergebnisse einer Versuchsreihe mit unterschiedlichen Eingriffsverhältnissen, einer Referenzuntersuchung sowie deren Auswirkungen auf die entstehenden Bauteilschädigungen vorgestellt.


[ 28 ] Schulze, V.; Deuchert, M. & Ruhs, C. (2009), "Compensation of the size effect due to the cutter radius offset in the micro milling process". Eds. 4M and ICOMM Associations, Charlesworth Group, pp. 437-440.
Abstract:
By the transfer of processes and technologies into the microarea the influences of physical effects change. This effect is called size effect. This paper deals with the size effect of the tool’s cutter radius offset. The radial run out inaccuracies of the spindle, the clamping system, and the tool itself, can result in a deflection of the cutting edges up to 20 µm. These tolerances cannot be scaled in the same way like the reduction of the tool diameter. This size effect in the microarea can be shown by drawing the tool diameter versus the relation of the typical radial run out to typical feed per tooth. With a tool diameter of 1 mm a relation of the cutter radius offset is still evident to the feed per tooth of approximately 0.6. It signifies highly unbalanced loads on the cutting edges because of the changing chipping thicknesses. This leads to raised tool wear, high trepanning forces and finally to a low process reliability. There are two possibilities to eliminate this size effect. The first one is, to use only an one edged cutting tool. This paper shows an optimized geometry for one edged micro milling cutters. A second possibility to eliminate this size effect, a new approach for a fine compensation of a multiple cutting edge tool’s cutter radius offset, was analyzed. Therefore the cutter radius offset of customized two-edged tools of a diameter of 100 µm has been measured in the clamped state and afterwards minimized to 2-4 µm. In a further step a fine compensation grinding process was developed and tested.


[ 29 ] Schulze, V.; Authenrieth, H. . & Kühlewein, C. (2011), "Understanding and Optimization of the Skiving Process by use of 3D-FEM-Simulation". Eds. CIRP, pp. 5.

[ 30 ] Schulze, V. & Zanger, F. (2011), "Development of a Simulation Model to Investigate Tool Wear in Ti-6Al-4V Alloy Machining". Modelling of Machining Operations, eds. Trans Tech Publications, Trans Tech Publications, pp. 535-544.
Abstract:
Titanium alloys like Ti‑6Al‑4V have a low density, a very high strength and are highly resistant to corrosion. However, the positive qualities in combination with the low heat conductivity have disadvantageous effects on mechanical machining and on cutting in particular. Ti‑6Al‑4V forms segmented chips for the whole range of cutting velocities which influences tool wear. Thus, optimization of the manufacturing process is difficult. To obtain this goal the chip segmentation process and the tool wear are studied numerically in this article. Therefore, a FEM model was developed which calculates the wear rates depending on state variables from the cutting simulation, using an empirical tool wear model. The segmentation leads to mechanical and thermal load variations, which are taken into consideration during the tool wear simulations. In order to evaluate the simulation results, they are compared with experimentally obtained results for different process parameters.


[ 31 ] Schulze, V.; Zanger, F.; Michna, J.; Ambrosy, F. & Pabst, R. (2011), "Investigation of the machining behavior of metal matrix composites (MMC) using chip formation simulation". Modelling of Machining Operations, eds. Trans Tech Publications, Trans Tech Publications, pp. 20-29.
Abstract:
The machining of metal matrix composites (MMC) induces cyclic loadings on tools, which creates new challenges for machining. In particular the distributed reinforcement, consisting of silicon carbide (SiC) or aluminum oxide (Al2O3), evokes especially high mechanical loads. The development of metal matrix composites is pointing towards higher fractions of reinforcements, which affects the resulting forces and temperatures. In this regard the influence of varying particle filling degrees, particle diameters, cutting velocities and tool geometries in terms of rake angle and cutting edge radius have been investigated by means of cutting simulation. For the process a self-designed continuous remeshing routine was used for which a dual phase material behavior has been implemented. The developed simulation model enables investigations of the machining behavior of metal matrix composites to the extent that ideal process strategies and tool geometries can be identified by multiple simulations.


[ 32 ] Schulze, V.; Michna, J.; Zanger, F. & Pabst, R. (2011), "Modeling the Process-Induced Modifications of the Microstructure of Work Piece Surface Zones in Cutting Processes". Modelling of Machining Operations, eds. Trans Tech Publications, Trans Tech Publications, pp. 371-380.
Abstract:
Cutting processes lead to mechanical and thermal loading of tool and work piece. This loading entails a direct influence of the cutting process on the surface layers of the manufactured work pieces. As a result, residual stresses and modifications of the micro-structure like white layers can occur in surface-near zones of the work piece. This paper presents the development of a FE-simulation model to predict phase transformations due to cutting processes. Therefore a 2D-FE-cutting simulation including a dynamic re-meshing is combined with a simulation routine to describe phase transformations that was primarily developed to simulate laser hardening. This paper illustrates the implemented mechanisms to determine phase transformations considering short time austenization and shows first experimental results revealing the influence of process parameters on the surfaces microstructure.


[ 33 ] Schulze, V.; Osterried, J.; Meier, H. & Zanger, F. (2011), "Simulation of Multiple Chip Formation when Broaching SAE 5120 Low Alloy Steel". Modelling of Machining Operations, eds. Trans Tech Publications, Trans Tech Publications, pp. 37-45.
Abstract:
The paper aims to predict component conditions after each subprocess of a manufacturing process chain. A continuous simulation has to be achieved, considering the inheritance of component states. To identify functional descriptions between component conditions as input and output quantities a broaching simulation is being developed. It includes multiple chip formation with multi-toothed broaching tools and machining history of a component as well. For this purpose component conditions are extracted from and transferred to a workpiece model as an initial condition. The 2D finite element chip formation model uses remeshing for material separation allowing highly detailed surface layer characterizations. Parallel experimental studies vary process parameters, whose objective is optimization of process control and forecast of component properties. Characterization of component conditions is based on distortion analysis, cutting force and surface measurements. Comparing the specific cutting forces between simulation model and performed experiments show a reasonable agreement of results.


[ 34 ] Lanza, G.; Schulze, V.; Stockey, S. & Chlipala, M. (2011), "Manufacturing and Quality Assurance of Micro Structured Crankshaft Bearings". Proceedings of 11th International Conference of the European Society for Precision Engineering & Nanotechnology, eds. European Society for Precision Engineering & Nanotechnology, Sieca Repro, pp. 183-186.
Abstract:
This paper focuses on the manufacturing of microstructures for the enhancement of friction loaded surfaces of a crankshaft. The studied structures are presented and an approach for the quality assurance of the microstructures is explained. This approach is based on the assessment of the neighbourhood distances between the single measurement points within a measurement point cloud and the application of edge detection to classify the detected form deviations.


[ 35 ] Schulze, V.; Deuchert, M.; Ruhs, C.; Weber, P. & Weingärtner, R. (2011), "Fertigungstechnologien zur Erzeugung hochgenauer Mikrostrukturen und Oberflächen". KIT Scientific Reports, pp. 65-74.
Abstract:
Um Mikrokavitäten für urformende Prozesse herzustellen, sind das Mikrozerspanen, die Mikrofunkenerosion und das Mikrolaserabtragen verbreitete Technologien, die für ein sehr breites Materialspektrum und eine breite Größenskala geeignet sind. Darüber hinaus existieren Ansätze zur Nachbehandlung, wie das elektrochemische Abtragen, um die Mikroformeinsätze nachträglich zu optimieren. In der abschließenden Phase des Sonderforschungsbereichs 499 wurde dem Projektbereich der Arbeitsvorbereitung zum Ziel gesetzt, die Genauigkeit der Verfahren zu steigern und gleichzeitig eine hohe Prozesssicherheit zu gewährleisten. Durch die Integration entsprechender optischer und akustischer Messtechnik in die Werkzeugmaschinen wurde für die abtragenden Verfahren jeweils eine spezifische Prozessregelung entwickelt, um beim Laserabtragen die Fokuslage zu regeln und bei der Mikrofunkenerosion eine werkzeugverschleißbedingte Tiefenabweichung der gefertigten Kavität zu detektieren und zu kompensieren. Die erzielten Ergebnisse wurden kontinuierlich auf den kombinierten Laser/EDM-Bearbeitungsprozess übertragen. Zur Optimierung der gefertigten Formeinsätze wurde das elektrochemische Abtragen zur Steigerung der Oberflächengüte und Entfernung von Graten entwickelt und eine entsprechende Maschine aufgebaut. Um das im SFB 499 erarbeitete Wissen in die Industrie zu transferieren, wurde in der gegenwärtigen Phase ein Transferbereich eingerichtet. Hier wurden in Kooperation mit den Firmenpartnern neue praxisnahe Studien, Technologien und Produkte umgesetzt.


[ 36 ] Schulze, V.; Osterried, J. & Meier, H. (2011), "Influence of multiple chip formation on surface layer conditions in a simulative broaching study". Pp. 481-488.
Abstract:
A continuous simulation of a process chain is an overall goal, allowing a forecast of component characteristics. This work focuses on modelling the sub process broaching, respecting multiple chip formation by a multi-edged broach. A 2D finite element model has been developed for Abaqus/ Standard with thermo-mechanical elements and remeshing to describe the material separation. Small element sizes lead to a highly detailed surface layer description. A methodology for taking multiple chip formation into account is described. The mechanically unstressed surface layer condition occurring behind the cutting edge after machining is extracted. User routines transfer information about stress, strain and temperature to an unmachined workpiece model. Chip formation is simulated repeatedly. The development of the simulation model is done parallel to experimental studies. Experiment and simulation results show a good correlation. First results for sequential cuts show that the surface layer condition is affected by the number of sequential cuts.


[ 37 ] Schulze, V.; Pabst, R. & Meier, H. (2011), "Research Training Group 1483 - Process chains in manufacturing: Interaction, modelling and evaluation of process zones". Pp. 421-428.
Abstract:
The basic intention of the Research Training Group 1483 is the description and optimization of process chains in manufacturing. It is subdivided into three research areas. Research area B focuses on solid components in the process chain of soft- and hard machining realized by broaching with an intermediate heat treatment. After the broaching process, the induced residual stresses, work hardening and the component is microstructure are characterized to generate a functional relationship between process parameters and component condition. These descriptions are used in simulations which are analysed parallel to machining experiments to map the component history and the influence of previous machining on the component. Heat treatment in experiment as well as in simulation is realized by case- and induction hardening. Carbon diffusion and martensite formation result from simulation by the phase field method. This article shows first results of the chipping process and heat treatment process.


[ 38 ] Schulze, V. & Weber, P. (2011), "Acoustical focal positioning for micromachining using a picosecond pulsed UV-Laser". Pp. 966.
Abstract:
Picosecond pulsed UV-lasers enable micromachining down to a few microns in nearly all kinds of solid materials like metals, ceramics and polymers. However, precise machining results with high surface quality require a defined sublimation process [1]. Problems arise by accurate focal positioning on the work piece surface and by decreasing laser power for long machining times caused by laser and temperature influence on optics and thus misalignment. Therefore, control units for monitoring and controlling of significant process parameters like focal position and laser power are necessary. While laser ablation emitted acoustic airborne-sound emissions are used for the control unit. A precise adjustment of the focal depth which is +/-20 μm onto the work piece surface has been investigated for cemented carbide and an Al2O3+ZrO2-ceramic by recording of acoustic emissions. The analysis of the airborne-sound emissions by Fast Fourier Transformation gives information about the frequency spectrum and the correlation to the focal position. A subsequent fitted algorithm search allows an automated acoustical focal positioning. Furthermore, a power measuring instrument has been integrated into the working area for automatically measuring and adjusting of actual laser power at the focal spot due to the fact that the laser power has to be kept constant for acoustical focal positioning.


[ 39 ] Schulze, V.; Weber, P. & Ruhs, C. (2011), "Optical and acoustical process control in hybrid micromachining using a picosecond pulsed UV-laser and micro EDM-milling". Eds. 4M Association, Research Publishing, pp. 83-86.
Abstract:
The manufacturing processes, micro Electrical Discharge Machining (EDM) and micro Laser Beam Machining(LBM), allow a quasi-force- and contact-free machining of numerous materials, regardless of their hardness like hardened tool steels and cemented carbides. Hybrid machining with both processes allows the combination of the process specific advantages while disadvantages can partially be eliminated. Specific advantages of EDM are the achievable high aspect ratios and high processing speeds compared to LBM. However, EDM is limited in miniaturization due to the smallest available electrode diameter while LBM has a high miniaturization potential due to small laser focal spots down to 3 μm and any material regardless of conductivity can be processed by LBM. Especially for hybrid machining of EDM and LBM the process stability and reliability have to be guaranteed anytime for both processes. At the wbk Institute of Production Science a hybrid EDM/LBM-machine has been developed and built up for the combined ablation on a single machine without reclamping of the work piece which is necessary for accuracy increase of ablated structures. The increase of process reliability in the micro-machining processes EDM-milling and laser ablation is presented by using optical and acoustical on-machine sensors for control systems and new control methods. For each machining technology the process controls are explored and transferred to the combined process. Concluding a micro structure from cemented carbide is machined as a demonstrator for precise combined micro machining of EDM and LBM.


[ 40 ] Schulze, V.; Chlipala, M. & Pabst, R. (2011), "Integration of a picosecond laser system into a machinig centre". Pp. 1121-1125.
Abstract:
The application of fuel saving technologies like fuelefficient engine oil or the implementation of an automated start-stop system into the engine management leads to increased loadson power train bearings. To improve the durability of these parts, the friction surfaces need to be modified. The optimization of already existing parts can be done by microstructuring of the surfacee.g. via laser ablation. This structuring leads to an improved tribological behavior due to an increased hydrodynamic pressure gain,thus disconnecting the friction partners even with oil of low viscosity. In order to reduce process time and improve the energy footprint of the process chain with an additional process, the aim of this work is to integrate the laser structuring into a multi process machine. In order to realize the laser ablation without surface damage which is caused by heat input and therefore leads to microstructural transformation, the laser system has to have a pulse duration smaller than 10 picoseconds. The use of such laser systems leads to challenges regarding the beam guidance which is not achievable by glasfibres because of the high pulse peak output exceeding the damage threshold. The guidance therefore has to be implemented by deflection mirrors and integrated into the machining centre.


[ 41 ] Schulze, V.; Boev, N. & Zanger, F. (2012), "Simulation of Metal Cutting Process with Variable Cutting Thickness During Broaching ". Procedia CIRP 1, eds. Konrad Wegener, pp. 437-442.
Abstract:
With the advancements of different simulation approaches several metal cutting processes have been simulated, investigated and improved. However, very little work has been published in the field of metal cutting with variable cutting thicknesses by means of cutting simulations. This paper presents a 2D cutting simulation approach using the finite element method (FEM), which is applied in order to predict cutting forces, temperatures and chip shapes while broaching. To investigate the influence of varying cutting thicknesses the broaching process is simulated with different constant cutting thicknesses at the beginning (20, 35 μm and 50 μm).


[ 42 ] Schulze, V. & Zanger, F. (2011), "Numerical Analysis of the Influence of Johnson-Cook-Material Parameters on the Surface Integrity of Ti-6Al-4 V ". Procedia Engineering 19, eds. Prof. E. Brinksmeier, pp. 306-311.
Abstract:
During machining metals the material of the work piece is highly deformed and heated, which influences surface integrity. To simulate the machining process the thermo-mechanical material behavior in dependence of strain, strain rate and temperature has to be well known. One of the most used material models is the Johnson-Cook-Model, where the material dependent parameters are determined by Split-Hopkinson pressure bar tests. For the titanium alloy Ti-6Al-4 V used for the simulations different investigations with the goal of determining material parameters have been published. However, the presented results vary significantly. It is expected that these varying parameters result in different predictions of surface integrity after machining. This influence is investigated by machining simulations using a self-developed continuous remeshing method.


[ 43 ] Schulze, V.; Osterried, J. & Strauß, T. (2012), "FE analysis on the influence of sequential cuts on component conditions for different machining strategies". Procedia Engineering 19(2011), eds. CIRP, pp. 318-323.
Abstract:
Performance and durability of highly stressed components are greatly affected by the component’s state including residual stresses. For processes with multi-edged tools, sequential cuts influence the surface layer. A method to forecast the component state is developed by using FE simulations of multiple chip formation done by broaching of SAE 5120 low alloy steel. Remeshing describes material separation, allowing a high detailed resolution of the machined surface layer including the workhardened layer and the residual stress state. Implemented simulation method extracts information from the machined work piece and defines initial conditions for a new unmachined work piece model. The work analyses the influence of tool temperatures on residual stress states after machining. Effects on the stresses appear below the surface. The results are compared to residual stress measurements.


[ 44 ] Schulze, V.; Pabst, R. & Meier, H. (2012), "Influence of broaching for evaluation of process chains". Eds. Summer School 2011, G. S. 1., KIT Scientific Publishing, pp. 1-4.
Abstract:
Broaching is a highly effective manufacturing method to create complex structures on inner or outer surfaces. It is characterized by short machining times, simple machine technique and high automation. To identify the effects of broaching on the components, eperiments with different tools and cutting speeds have been performed on SAE 5120 low alloyed steel. Parts machined with determined sets of process parameters have been subjected to a subsequent case hardening step to show the effect of residual stress formation after broaching to potentials of distortion. In addition, the influence of the tool´s minor cutting edges to the formation of cutting forces has been shown.


[ 45 ] Lanza, G.; Schulze, V.; Stockey, S.; Chlipala, M. & Haefner, B. (2012), "Automated Measurement Data Analysis for Micro Structured Surfaces". Proceedings of 12th International Conference of the European Society for Precision Engineering & Nanotechnology, eds. European Society for Precision Engineering & Nanotechnology, Sieca Repro, pp. 235-238.
Abstract:
Microstructures applied to the surface of a friction bearing are able to improve the behavior of the part. Due to the challenges regarding the production processes of microstructured surfaces an automated and user-independent in-line quality assurance can make a contribution to improve the production processes significantly. Therefore a three stage measurment filter was developed in order to automatically detect microstructures on the surface even under the restriction of a bad signal-noise ratio.


[ 46 ] Helu, M.; Behmann, B.; Meier, H.; Dornfeld, D.; Lanza, G. & Schulze, V. (2012), "Total Cost Analysis of Process Time Reduction as a Green Machining Strategy". Eds. Dornfeld, Springer, pp. 299-304.
Abstract:
Manufacturers have pursued green machining strategies, such as process time reduction, to address the demand for environmental impact reduction. These strategies, though, increase the stresses on the manufacturing system, which can affect availability, service life, achieved part quality, and cost. This study presents a total cost analysis of process time reduction for titanium machining to holistically consider the implications of such strategies. While the results suggest it may not be a viable green machining strategy for titanium machining, the feasibility of process time reduction as a greening solution is highly dependent on the functionality of the finished part.


[ 47 ] Schulze, V. & Weber, P. (2012), "Automated laser power control for roughing and finishing in micro laser machining". Proceedings of the 9th International Conference on Multi-Material Micro Manufacture, eds. 4M Association, Research Publishing, pp. 43-46.
Abstract:
Micro laser machining with ultra short pulsed Nd:YAG lasers enables micro structuring in nearly all kinds of solid materials regardless of their mechanical properties. Due to the high focusing possibility of laser beams smallest structures in the micro meter region can be realized with small heat affected zones. The drawback of the high miniaturization potential is the high machining time for machining of lager volumes. As a remedy new ablation strategies have been investigated. Roughing is used for ablation of high volumes with short ablation times while finishing is used for generation of the desired surface quality. High ablation rates for roughing can be achieved with high laser power densities in focal depth. It is influenced by the focal spot diameter and the laser power in focal depth which have to be controlled and adjusted in process. For the manipulation of the laser focal spot diameter an automated beam expander has been integrated into the laser beam path. Additional laser power control units (e.g. using acoustic emissions) allow the automated adjustment of laser power in focal depth for different focal diameters.


[ 48 ] Schulze, V.; Hoppen, P.; Ruhs, C. & Weber, P. (2012), "Micro structuring of Zr-based bulk metallic glasses". Proceedings of the 9th International Conference on Multi-Material Micro Manufacture, eds. Humbert Noll, S. D., Research Publishing, pp. 144-147.
Abstract:
Bulk metallic glasses have very interesting mechanical properties due to the fact that they have an amorphous grain structure which results from high cooling rates during fabrication. But they lose their properties when high temperatures occur during machining because of the crystallization of the material. The challenge for machining bulk metallic glasses is to find suitable parameters which lead to a low tool wear as well as a good surface quality and to avoid crystallization at the same time. In this paper a micro milled Zr-based bulk metallic glass is analyzed and discussed. In addition, the material was machined by the thermal processes micro electrical discharge machining and micro laser ablation and the influence of the heat input on the metallographic structure is evaluated. With all three micro production processes the BMG could be structured with little tool wear and without crystallization.


[ 49 ] Schulze, V. & Weber, P. (2012), "Laser focus positioning Using acoustical Emissions while micromachining". Pp. 1-26.
Abstract:
Picosecond pulsed UV-lasers enable micromachining down to a few microns in nearly all kinds of solid materials like metal, ceramic, glass and polymer. Precise machining results with high surface quality require a defined sublimation process. Problems arise by accurate focal positioning on the work piece surface. Varying surface conditions as reflective surfaces for polished work pieces, transparent surfaces of glass, white surfaces of ceramics etc. are often a challenge for optical focal positioning approaches. Therefore, an alternative control unit for monitoring and controlling of focal position has been investigated by using acoustical emissions while machining. A precise adjustment of the focal depth which is +/-20 µm onto the work piece surface has been realized for cemented carbide WC-12Co and ceramic Al2O3+ ZrO2 by recording and analysis of acoustic air-borne sound emissions. The analysis of the airborne-sound emission shows a correlation between the frequency spectrum and the focal position. A subsequent fitted algorithm search allows an automated acoustical focal positioning. Currently new strategies in medical application are pursued in the field of bone cutting with boundary detection analyzing acoustic emissions.


[ 50 ] Schulze, V.; Boev, N. & Zanger, F. (2012), "Numerical Investigation of the Changing Cutting Force Caused by the Effects of Process Machine Interaction While Broaching ". Procedia CIRP 4, eds. Prof. Eiji Shamoto, pp. 140-145.
Abstract:
During broaching, interactions between the process and the machine are inevitable and affect the process itself and the resulting work piece. To understand these effects profoundly, they have to be analyzed and investigated. One of these effects is the vibration of the cutting edge which results for example in a change in rake angle or cutting thickness during the cutting process. Therefore, the first part of this paper presents results o f investigations concerning a variable cutting thickness and the second includes investigations of the variable rake angle during broaching, in both cases the effects on the cutting forces by means of two-dimensional (2D) cutting simulations.


[ 51 ] Schulze, V.; Michna, J.; Schneider, J. & Gumbsch, P. (2012), "Modelling of cutting induced surface phase transformations considering friction effects". Eds. CIRP, pp. 331-336.
Abstract:
Depending on machining process, machined material, cutting and tool parameters as well as the resulting heating and cooling rates the heat in cutting processes can lead to phase transformations in the work piece surface layer. This paper presents an approach to predict and analyze cutting induced phase transformations in surface layers. Therefore a 2D-FE-cutting simulation model has been developed for the steel 42CrMo4 (AISI4140). The model includes remeshing for the material separation and a material model considering short time austenization and transformation plasticity. To verify the simulations and to determine necessary input data, orthogonal turning experiments are done and furthermore a laboratory tribometer is used to measure the friction coefficient of the sliding pair between the hard metal cutting tool (WC-6Co) and the steel as a function of sliding speed and temperature.


[ 52 ] Schulze, V.; Hoffmeister, J.; Zanger, F.; Ambrosy, F. & Erz, A. (2012), "Development of a microstructured deep rolling tool for generation of nanocrystalline surface layer". Topical Meetings Structured & Freeform Surfaces , eds. European Society for Precision Engineering & Nanotechnology, pp. 57-80.
Abstract:
The focus of this paper is the development of a modified deep rolling tool. Here, the effects of the variation of the roller surface microstructuring are studied. After machining with the modified tool the work piece surface shall remain plane and without microstructures, whereas the grain size in the surface layer shall be reduced drastically. A negative influence on fatigue life is possible due to a folding of the material on the work piece surface attributed to discontinuous deformation. Multiple EDM process variations were used to define microstructures on the roller surface, which increase shearing at the work piece and initiate the formation of a nanocrystalline surface layer during the deep rolling process.


[ 53 ] Schulze, V.; Zanger, F. & Ambrosy, F. (2013), "Investigation of the Impact of Orthogonal Cutting Processes on Nanocrystalline Surface Layer Generation". The Current State-of-the-Art on Material Forming, eds. Trans Tech Publications, pp. 2009-2020.
Abstract:
The present work analyzes the influence of an orthogonal machining process on the generation of nanocrystalline surface layers. Thereby, AISI 4140 is used as work piece material. Metallic parts with a severe nanocrystalline grain refinement in the near-surface area show many beneficial properties. Such surface layers considerably influence the friction and wear characteristics of the work piece in a subsequent usage as design elements working under tribological loads. The focus of this paper is an experimental analysis of a finishing orthogonal cutting operation, carried out with a broaching machine, to generate nanocrystalline surface layers. The influence of process and geometry parameters on the generation of nanocrystalline surfaces is investigated with the aim to massively decrease the grain size in the work piece surface layer. Parameters that are studied and taken into account in the manufacturing process are cutting edge radius r_beta, depth of cut h and cutting velocity vc. The cutting edge radius r_beta is modified by a drag finishing process. The generation of nanocrystalline surface layers is especially influenced by the design of the uncoated carbide cutting tools. Additionally, cutting force Fc and passive force Fp are determined by a 3-component dynamometer to calculate the relationship between specific cutting force kc and specific passive force kp. The temperature beneath the clearance face is detected by a fiber optic pyrometer. These measurement methods and devices are applied to detect the impact of the most relevant measurement values occurring during machining and causing a drastic reduction of grain size in the surface layer. The evaluation of the manufacturing process is carried out by detailed analyses of the microstructural conditions in the surface layer after processing using a Focused Ion Beam (FIB) system. These material characterizations provide information about the surface engineering concerning the microstructural changes in the surface layer of the work piece due to finishing orthogonal cutting processes.


[ 54 ] Schulze, V.; Zanger, F.; Krausse, M. & Boev, N. (2013), "Simulation Approach for the Prediction of Surface Deviations Caused by Process-Machine-Interaction During Broaching ". Procedia CIRP 8, eds. Prof. Luca Settineri, pp. 252-257.
Abstract:
Broaching is a highly efficient metal machining process in mass production. Parts with high quality requirements are manufactured by broaching, which can be influenced by different factors. One of them is vibration caused by process-machine-interactions. Such vibrations can easily be investigated with external broaching, where these vibrations result in varying process forces and wavily profiled machining surfaces. This paper presents a 2D FEM-simulation approach for the prediction of surface rough-ness generated by broaching. In the simulation model, the solid machine structure that consists of a large number of machine parts is realized by using elements representing the stiffness and the dynamic properties of the machine structure. Thus, it is possible to avoid high calculation times. The broach is implemented as an elastic body and the resulting process forces are realized by an analytical model that considers the process parameters cutting thickness, cutting velocity and rake angle. These process parameters are calculated for each increment, which allows determining the resulting process forces and applying them onto the teeth. Finally, the presented simulation approach for the prediction of the surface roughness generated by broaching is validated by means of experiments. Broaches with different numbers of teeth are used for the experimental setup.


[ 55 ] Zanger, F. & Schulze, V. (2013), "Investigations on Mechanisms of Tool Wear in Machining of Ti-6Al-4V Using FEM Simulation". Procedia CIRP 8, eds. Prof. Luca Settineri, pp. 158-163.
Abstract:
The titanium alloy Ti-6Al-4V is used very often for highly stressed components like compressor wheels because of its excellent mechanical and thermal properties. However, when machining components made of Ti-6Al-4V, their high tensile strength in combination with a low Young's modulus and a low thermal conductivity leads to high thermal and mechanical stresses in the cutting tools, which in turn lead to a particularly fast tool wear. Thus, optimization of the manufacturing process is required. However, to obtain this goal the mechanisms of tool wear were studied numerically and some results are presented in this article. Ti-6Al-4V forms segmented chips for the whole range of cutting velocities. The mechanical and thermal load variations due to the segmentation are taken into consideration during these investigations. A FEM model using a self-developed continuous remeshing method to form segmented chips was developed. Thus resulting state variables like stresses, temperatures and relative velocities between the tool face and the chip along the cutting tool can be investigated, which are well known for influencing tool wear in machining. The distributions of these state variables along the cutting tool, especially in the area of the cutting edge, are analyzed and related to experimentally caused tool wear. In order to evaluate the developed simulation model, orthogonal cutting experiments have been conducted with uncoated carbide (WC/Co) cutting tools. Simulated results are compared with experimentally obtained data for different process parameters.


[ 56 ] Schulze, V.; Zanger, F.; Michna, J. & Lang, F. (2013), "3D-FE-Modelling of the Drilling Process – Prediction of Phase Transformations at the Surface Layer ". Procedia CIRP 8, eds. Prof. Luca Settineri, pp. 33-38.
Abstract:
Due to friction, plastic deformation and cutting, the drilling process leads to high mechanical and thermal loadings of drilling tool and workpiece. Distortion and modifications of the surface layer microstructure, especially rehardened zones, can be observed, whereby the experimental investigation of correlations between machining processes and resulting surface layers are very complicated and time consuming. This paper presents a numerical approach to predict machining induced phase transformations at the surface layer of drilled holes. Based on experimental results and 2D FE machining simulations, an abstract model representing the mechanical and thermal collective load of the drilling process has been developed in relation to the parameters cutting speed and feed rate. To predict phase transformations of the steel 42CrMo4 (AISI 4140) at the surface layer of drilled holes a 3D FE-model has been established using the commercial software ABAQUS. The kinetics of the phase transformations are implemented using specific user subroutines. The model calculates the process of austenization and the transformed volume fraction of the phases ferrite/perlite, bainite and martensite and also considers transformation plasticity and the resulting hardness of the microstructure. By simulating different combinations of cutting parameters, relations between drilling process and resulting surface layers of drilled holes have been studied. In addition the machining induced distortion of the workpiece can be calculated simultaneously. The simulation model has been verified by drilling experiments, thermal imaging and metallographic investigations. Predicting machining induced surface layer states, the functionality of future components can be improved.


[ 57 ] Schulze, V.; Zanger, F. & Boev, N. (2013), "Numerical Investigations on Changes of the Main Shear Plane while Broaching ". Procedia CIRP 8, eds. Prof. Luca Settineri, pp. 246-251.
Abstract:
The quality of broached components can be influenced by different factors, such as am-bient temperatures, human factors or vibrations of the machine structure induced by process-machine-interactions. These vibrations are normally initiated by changing pro-cess forces, which are mainly caused by cutting thickness or rake angle variations. Broached components are produced within one motion of the broach along the surface of the work piece, where multiple teeth in a row are in contact. The variation of the cut- ting thickness results from a wavy profile on the surface generated by the previous cut-ting process or the previous tooth. When the cutting thickness changes during the process, the rake angle varies, too. In some further published works, the changing cutting thickness and the changing rake angle during broaching were investigated by means of machining simulations with the result that the process forces are still adjusting after the cutting thickness and the rake angle have already reached a stable value. The adjustment of the shear plane on the new cutting conditions is mentioned as the main reason. This paper presents some deeper investigations on this effect. Therefore, 2D machining simulations for different cutting thicknesses and cutting velocities are performed. The investigations show tendencies for the still adjusting shear plane after changing the cutting thickness or the rake angle during the cutting process. Finally, the simulation results are validated with experimentally observed data.


[ 58 ] Schulze, V.; Zanger, F. & Ambrosy, F. (2013), "Quantitative Microstructural Analysis of Nanocrystalline Surface Layer Induced by a Modified Cutting Process". WGP Congress 2013, eds. Trans Tech Publications, pp. 109-115.
Abstract:
Present work analyzes the influence of process and modified geometry parameters of an orthogonal final machining process (finishing) on the nanocrystalline surface layers generation by quantitative microstructural analysis. Thereby, AISI 4140 (German Steel 42CrMo4) in a state quenched and tempered at 450°C is used as workpiece material. Metallic materials used in technical applications are polycrystalline in nature and are composed of a large number of grains which are separated by grain boundaries. The grain size has a strong influence on the mechanical material properties. Metallic parts with a severe nanocrystalline grain refinement in the near-surface area show many beneficial properties. Such surface layers considerably influence the friction and wear characteristics of the workpiece in a subsequent usage as design elements working under tribological loads due to their extreme superplastic properties. The tribologically induced surface layers formation already starts during the manufacturing of the components, by leading to a change of workpiece material near the surface. Particularly when the depth of cut h becomes of the same order as the cutting edge radius r_beta, the ploughing process becomes increasingly important and strongly influences the chip formation process. The plastic zone depth within the surface layer is especially influenced by the design of the microgeometry of the cutting tools and increases almost linearly with the ratio of cutting edge radius r_beta to depth of cut h. The plastic zone is hereby approximately of the same order of magnitude as the cutting edge radius r_beta. Parameters that are studied and taken into account in the manufacturing process are cutting edge radius r{\ss }, depth of cut h and cutting velocity vc. Variations of cutting depth h are performed in a range of 30 to 100 µm and variations of cutting edge radius r_beta are executed in a range of 30 to 150 µm. The microgeometries of the tools are preconditioned by abrasive grinding with a drag finishing machine and observed by a confocal light microscope. A cutting velocity vc of 25 and 150 m/min is applied. The evaluation of the manufacturing process is carried out by detailed analyses of the microstructural conditions in the surface layer after processing using a Focused Ion Beam system. These material characterizations provide information about the surface engineering concerning the microstructural changes in the workpiece surface layer due to machining. Hereby, the grain size analysis is investigated by a line method based on the characterization of portions of several test-lines positioned across the two dimensional Focused Ion Beam images.


[ 59 ] Schulze, V.; Arrazola, P. J.; Zanger, F. & Osterried, J. (2013), "Simulation of Distortion Due to Machining of Thin-walled Components ". Procedia CIRP 8, eds. Prof. Luca Settineri, pp. 45-50.
Abstract:
The distortion of components is strongly related to the residual stress state induced by manufacturing processes like heat treatment, forming or machining. Each process step affects the initial stress state of the following process step. When removing material during machining, the component establishes a new stress equilibrium. Stresses are redistributed causing the component geometry to adjust. Especially for thin-walled components distortion potential is high. Gaining knowledge about the influence of initial loads and the release of distortion during machining processes helps to increase product quality and efficiency. The influences of different initial stress states and different machining parameters on the amount of distortion are examined using both FEM simulations and experiments. A thin-walled T-profile made of aluminum alloy Al 7075-T6 serves as test specimen. A bending process applies a load to initialize a repeatable and defined residual stress state. A groove was machined afterwards into the plastically deformed work piece to trigger stress redistribution and a release of distortion. Different loads with 35 to 45 kN and two different geometries of a groove were used. The amount of initial stress has a significant effect on the distortion potential which could be quantified in the study. Simulations show the same behavior as the experiments and the results match very well especially for a high load.


[ 60 ] Ambrosy, F.; Zanger, F.; Schulze, V. & Jawahir, I. (2014), "An Experimental Study of Cryogenic Machining on Nanocrystalline Surface Layer Generation ". Procedia CIRP 13, eds. Prof. Dragos Axinte, pp. 169-174.
Abstract:
This paper presents an analysis of in-process liquid nitrogen cryogenic cooling on the generation of nanocrystalline workpiece (AISI4140) surface layer in machining. Samples from cryogenic machining demonstrate nanocrystalline grain refinement with beneficial properties, e.g., favorable wear characteristics. Correlations are established among process and geometry parameters, cooling conditions, cutting forces and surface layer states. Parameters studied are cooling state, depth of cut and cutting edge radius. Cutting forces are measured and a detailed analysis of micro/nano-structural surface layer conditions was carried out using Focused Ion Beam system, Atomic Force Microscopy and Nanoindentation. It is shown that the obtained micro/nano- structure strongly depends on the cooling conditions. In particular, the affected depth is influenced by the cooling state.


[ 61 ] Klotz, S.; Gerstenmeyer, M.; Zanger, F. & Schulze, V. (2014), "Influence of Clamping Systems During Drilling Carbon Fiber Reinforced Plastics ". Procidia CIRP, eds. Axinte, D., pp. 208-213.
Abstract:
During postprocessing of carbon fiber reinforced plastics, drilling is one of the mostly used machining processes. With increasing complexity of components the requirements on the clamping systems are rising. This paper shows the investigation of drilling tests fordifferent types of clamping positions which are examined regarding their influence on the resulting workpiece quality. The clamping of the planar specimens was realized by 3 and 4 points and by a ring clamping system with variable distances from the drill axis to the fixed points. During the experiments the process forces were measured and the resulting delamination and fiber pullouts at the workpiece surface were determined. The results demonstrate that the distance from the drill axis to the fixed points has a significant influence on the process forces and the achievable workpiece quality.


[ 62 ] Zanger, F.; Boev, N. & Schulze, V. (2014), "Surface Quality after Broaching with Variable Cutting Thickness ". Procedia CIRP 13, eds. Prof. Dragos Axinte, pp. 114-119.
Abstract:
During machining, new surfaces are generated. Depending on the machining process, different qualities of surfaces are produced. After broaching, a high surface quality is expected. However, the quality can be influenced by vibrations of the machine structure which leads to varying cutting thicknesses and thus to low surface qualities. The influence of variable cutting thicknesses during machining was investigated experimentally and by means of simulations. Dynamic changes in cutting thickness were considered as geometrical profiles on the uncut surfaces. Process forces were measured during the experiments and the roughness before and after broaching with one tooth was evaluated. The residual stresses in the workpiece surfaces were simulated with an already validated model of orthogonal machining using a self-implemented re-meshing method.


[ 63 ] Chlipala, M.; Stockey, S.; Hirtler, M.; Schulze, V. & Lanza, G. (2014), "Efficient ablation strategies and quality assurance for structuring big surfaces by an ultra-short-pulse laser". Proceedings of the 14th international conference of the european society for precision engineering and nanotechnology, pp. 170-173.
Abstract:
Owing to the high flexibility when using a laser beam as a tool, its field of applicationgrows more and more. In case of micro structuring of metal components especially the use of ultra short laser pulses offers a high potential for precise and high Quality results. However the economical application in an industrial surrounding is still affected by different issues, e. g. a lack of process efficiency. In this work, different factors and their influence on the ablation process are investigated for a improvement of the process efficiency for structuring micro-sized dimple structures on big metallic surfaces. To achieve this goal the repetition rate and the pulse strategy of the laser have to be in focus. Furthermore the interaction between consecutively produced holes and the heat accumulation for each hole were particularly taken into consideration. To constantly ensure the capability of the ablation process it is essential to measure and analyse the results of the process. This sets up the focus on a fast and reliable quality assurance of the ablated microstructures. Therefore this paper covers an automated evaluation approach for optical measurement data of microstructured surfaces in addition to the manufacturing approach.


[ 64 ] Schulze, V.; Zanger, F.; Deuchert, M. & Hoppen, P. (2013), "Compensating the cutting edge displacement during micro milling - a mechatronic approach". Proceedings of the 10th International Conference on Multi-Material Micro Manufacture, eds. Sabino Azcárate and Stefan Dimov, pp. 225-228.
Abstract:
The turnover of micro system technology (MST)-based products increases within the next years. This Ieads to the challenge of reliable processes with narrow tolerances. Processes as micro milling still have to deal with scale effects and narrow tolerances usually are only producible with high efforts. This article shows a mechatronic clamping system to compensate several inaccuracies at once. The cutting edge displacement results from inaccuracies in the machine tool , the clamping system and the milling tool. Compensating the cutting edge displacement while rotating with nominal rpm is an effective way to increase the accuracy up to 1 µm.


[ 65 ] Schulze, V.; Zanger, F. & Hoppen, P. (2014), "How to teach design for manufacturability at micro scale tasks". Proceedings of E&PDE 2013, eds. Lawlor, J.; Reilly, G.; Simpson, R.; Ring, M.; Kovacevic, A.; McGrath, M.; Ion, W.; Tormey, D.; Bohemia, E.; McMahon, C. & Parkinson, B., pp. 58-63.
Abstract:
Designing for manufacturability is a big challenge for every designer. Every manufacturing process has its characteristics and its limits. Costs and manufacturing time are often difficult to estimate, especially for engineers who do not cope with the daily problems of production processes. The relative tolerances are much higher when manufacturing on micro scale than on macroscopic scale and the production processes are generally less stable. An increasing number of products in different industries possess micro geometries and this trend will continue. Therefore the competence to design micro systems for manufacturability is getting more and more important for the next generation of designers. The wbk Institute of Production Science at the Karlsruhe Institute of Technology (KIT) is researching manufacturing processes on micro scale for more than 10 years. The institute is investigating processes such as micro milling, micro electric discharge machining, micro laser ablation and micro powder injection molding presently and will pursue this in future. Besides this research work the education of students in this field does have a high priority. Since about 10 years students are taught the basics of micro production processes and designing micro systems. Within the program of engineering studies a master course that comprises theory and application of micro systems is offered. This course consists of several lectures on the manufacturing processes at wbk and project work with one of the institute’s industry partners. This assures that the students get acquainted with the present problems of manufacturing on micro systems in the industry. Furthermore they learn designing for manufacturability as it is required in real world manufacturing processes.


[ 66 ] Schulze, V. & Hoppen, P. (2014), "Höchstpräzise Mikrozerspanung durch Kompensation des Schneidkantenversatzes". Pp. 30.

[ 67 ] Schulze, V. & Hoppen, P. (2014), "Innovative Werkzeuge für minimal-traumatische Operationen". Pp. 27.

[ 68 ] Meier, H.; Ninomiya, K.; Dornfeld, D. & Schulze, V. (2014), "Hard broaching of case hardened SAE 5120". Eds. CIRP, pp. 60-65.
Abstract:
To achieve knowledge of the effects of broaching to the component and the influence on subsequent process steps such as heat treatment and hard machining, broaching experiments were performed on plates made of normalized case hardening steel SAE 5120 in [1]. To investigate the effect of heat treatment, five broaching variants of [1] were chosen and hardened with two different case hardening depths, which were observed for effects generated from the surface layer carbon fraction. The hardened variants were analyzed for distortion generated through the hardening step and the specimen subsequently underwent a hard broaching stage in dry machining conditions. The cutting forces were monitored in-process, and the residual stress of the machined surface was determined using X-ray diffraction after the experiment. Surface roughness measurements also complemented the results. The results indicated that the cutting forces depend on existing distortion and therefore the volume material removed. It can also be seen that there is little influence on cutting forces with rising cutting speeds. Compressive residual stresses were present after heat treatment, but turned into tensile residual stress states after hard broaching. Effects from different case hardening depths and cutting speeds in the formation of surface roughness and residual stress could not be detected.


[ 69 ] Burtscher, J.; Fleischer, J. & Schulze, V. (2014), "Robot-based Guiding of Extrusion Profiles - Reduction of the Material Waste in the Manufacturing Process". International Conference on Sustainable Manufacturing (ICSM) , eds. Beijing Jigong Vogel Media Advertising, pp. 165-169.
Abstract:
The small batch production of space-frame-structures is realized with an innovative manufacturing process chain. This process chain allows the production of three-dimensionally curved extrusion profiles. Profiles are shaped directly after leaving the extrusion press and guided through the room by industrial robots. Currently profiles are extruded one at a time. The deficit of the actual manufacturing installation is the material waste at the beginning and at the end of the extrusion of one profile. To increase the sustainability, a new approach is to reduce this material waste through continuous manufacturing. An optimization algorithm for an automatic determination of the manufacturing sequence of diverse profiles was developed. In this way multiple profiles are produced in only one extrusion batch and the material waste is drastically reduced.


[ 70 ] Klotz, S.; Zanger, F. & Schulze, V. (2014), "Influence of clamping systems during milling of carbon fiber reinforced composites". New Production Technologies in Aerospace Industry, eds. Prof. Dr.-Ing. Berend Denkena, pp. 248-256.
Abstract:
Carbon fiber reinforced composites (CFRP) are mostly manufactured near net shape. Nevertheless, a final milling step at the edges of the cured components is still necessary. Damages which occur during milling or drilling of CFRP lower the durability of the components and increase the production costs. Requirements concerning the clamping system for milling or drilling CFRP are rising simultaneously with increasing complexity of the components. This stresses the need for complex clamping systems like linear clamping jaws around the whole workpiece. However such types of clamping systems induce poor accessibility to the component being worked on and hence longer machining time. As a result to the need for complex clamping systems, the production costs are increased. Therefore, several benefits can be achieved by increasing the distances between the clamping points of the clamping system to reduce machining time and production costs. This paper discusses investigations of milling tests with variable clamping conditions of the workpieces. In the experiments a linear milling operation the edge of the workpiece is examined. The clamping of the planar specimens was realized with a clamping system which enables the adjustment of different distances between the clamping points of the specimen. The process forces and the resulting damage at the workpiece surfaces were measured during the experiments. These results are compared with a linear clamping system to examine the influence of rising clamping distances. The results demonstrate that the distance of the clamping points while milling the edge of the workpiece has a significant influence on the process forces.


[ 71 ] Zanger, F.; Fellmeth, A.; Gerstenmeyer, M. & Schulze, V. (2015), "Influence of Kinematic Hardening during Machining of ARMCO Iron". Procedia CIRP, eds. Schulze, V., pp. 106-111.
Abstract:
The simpler implementation of isotropic hardening begs the question, if modelling kinematic hardening is necessary, especially if the hardening is nonlinear and temperature dependent. This question not only depends on the material, but also on the modelled load case, which varies with different manufacturing processes. To answer this, thermo-mechanically coupled elasto-plastic materials were used in an implicit material model in ABAQUS/Standard for a two-dimensional cutting simulation. The nonlinear hardening in the models varies from isotropic to mixed isotropic-kinematic hardening. The two-dimensional cutting simulation uses a two-dimensional continuous remeshing technique. A slow machining process was simulated leaving out strain rate and temperature dependencies and focussing purely on the kinematics of deformation. The necessity of a kinematically translated yield surface is concluded for iron, by comparing the purely isotropic to the mixed isotropic-kinematic hardening results. A comparison with experimental data illustrates the conformance quality of the different hardening modes.


[ 72 ] Bollig, P.; Faltin, C.; Schneider, J.; Schießl, R.; Maas, U. & Schulze, V. (2015), "Considering the Influence of Minimum Quantity Lubrication for Modelling Changes in Temperature, Forces and Phase Transformations during Machining". Procedia CIRP , eds. Volker Schulze , Elsevier, pp. 142-147.
Abstract:
The purpose of this study aims at presenting a method formodelling machining processes considering Minimum-Quantity-Lubrication (MQL) in a 2D and 3D-FEM-simulation by using the example of machining tempered steel AISI 4140. All parameters required for the FEM-simulation are calculatedwithin the multiphase simulation code INSFLA and the formula for the heat conduction coefficient is derived. To consider the influence of phase transformations of the fluid, separate experiments are performed. Furthermore, the frictioncoefficient is measured experimentally in dependence of the relative sliding velocity, contact pressureand temperature during machining with MQL as well as under dry conditions. The extended friction modelis used for the 2D and 3D models. MQLmachining experiments are performed for the purpose of validating these models. The main focus of the experiments is layed on cutting temperatures, forces and phase transformations on single workpieces.


[ 73 ] Zanger, F.; Boev, N. & Schulze, V. (2015), "Novel Approach for 3D Simulation of a Cutting Process with Adaptive Remeshing Technique ". Procedia CIRP 31, eds. Volker Schulze, pp. 88-93.
Abstract:
This paper presents an approach of a 3D cutting simulation with a continuous adaptive remeshing technique. Such a method allows the investigation of cutting processes without losing precious information. Furthermore, the developed 3D remeshing technique represents a possibility to investigate the effects caused by the secondary cutting edge in detail for more complex cutting processes. When a 3D model is built up to simulate the cutting process, an accurate meshing of the workpiece and the cutting edge is applied, which means that a large number of elements is generated. The presented remeshing method is applied only locally at regions, where distorted elements are located. This leads to a significant reduction of the calculation times compared to other remeshing techniques.


[ 74 ] Bejnoud, F.; Zanger, F. & Schulze, V. (2015), "Component Distortion due to a Broaching Process". Progress in Production Engineering, eds. Trans Tech Publications, pp. 239-246.
Abstract:
In order to obtain a better understanding of the effects of an internal broaching operation on the resulting component geometry, investigations were carried out. The investigations were carried out on sliding sleeves made of case hardening steel SAE 5115 (German grade 16MnCrS5). The cutting speed was varied. The results indicate that the arrangement of teeth on the scope of the tool has a significant influence on the resulting component geometry. Furthermore the results show that also the cutting speed has a significant influence on the resulting component geometry, in particular due to the resulting process temperatures.


[ 75 ] Hoppen, P.; Kacaras, A.; Matuschka, B. & Schulze, V. (2015), "Bearbeitung metallischer Gläser auf Fe- und Zr-Basis mittels Mikrofräsen, Mikrofunkenerosion und Mikrolaserabtragen". 7. Kolloquium Mikroproduktion, eds. Institut für Kunststoffverarbeitung, pp. 1-7.
Abstract:
Die Bearbeitung metallischer Gläser auf Zr- und Fe-Basis zur Herstellung technischer Oberflächen stellt die Fertigung vor zwei Herausforderungen: die Entwicklung eines stabilen Prozesses, um die benötigte Oberflächenqualität zu erzeugen und die Vermeidung von Kristallisation, um die Eigenschaften metallischer Gläser nicht zu verändern. Dabei hat sich gezeigt, dass die Bearbeitung von Proben auf Zr-Basis zu guten Ergebnissen führt, während dies bei Proben auf Fe-Basis nur unter bestimmten Randbedingungen möglich ist.


[ 76 ] Matuschka, B.; Schulze, V.; Rohde, M. & Seifert, H. (2015), "Leiterbahnen zur Versorgung von Leistungselektronik auf Spritzgegossenen, keramischen Grundkörpern". MikroSystemTechnik Kongress, eds. GMM - VDE/VDI-Gesellschaft Mikroelektronik, pp. 242-245.
Abstract:
Steigende Anforderungen an die Abmaße von Bauteilen aus der Automobilindustrie oder der Medizintechnik stellen die Verfahren der MID und 3D-MID Technik vor neue Herausforderungen. Um den Bauraum von elektronischen Komponenten mit mechanisch belastbaren Teilen zusammenzulegen, sind spritzgegossene Schaltungsträger eine wirksame Möglichkeit den Bauraum für die Komponenten zu vereinen. Die elektronischen Bauteile werden hierbei innerhalb der mechanisch belastbaren Strukturen untergebracht und verkapselt. Dies schützt die elektronischen Bauteile einerseits vor chemischen und thermischen Einflüssen, andererseits vor mechanischen Beschädigungen. Einen limitierenden Faktor stellt hierbei die Verbindungstechnik dar. Die Bauteile werden bisher mit Leiterplatten, Steckverbindern und Leadframes miteinander verbunden. Diese konventionelle Bauweise erlaubt allerdings einerseits nur bedingt den Einsatz von Leistungselektronik aufgrund von limitierten Leiterbahnquerschnitten und andererseits keine mechanisch und thermisch belastbaren Grundkörper, die den Bauraum von mechanischer Komponente und Elektronik vereinen. Diese Einschränkung wurde untersucht und ein möglicher Lösungsansatz dafür entwickelt. Als mechanisch belastbarer Grundkörper kommt eine Keramikstruktur, hergestellt durch Ceramic Injection Molding (CIM) zum Einsatz, welcher gleichzeitig später auch die integrierende Platzierung von elektronischen Bauteilen und Leiterbahnen ermöglicht. Im Grundkörper werden Aussparungen für Leiterbahnen zur späteren Versorgung von elektronischen Schaltkreisen und Leistungsverbrauchern wie z.B. High-Power LEDs oder mechatronischen Komponenten vorgesehen. Abbildung 1 stellt den Probenkörper schematisch dar. In einen keramischen Block wurden drei Leiterbahnpaare mit kleiner werdendem Querschnitt eingebracht. Die Nuten für die Leiter können bereits beim CIM Prozess oder durch eine spätere Nachbearbeitung produziert werden. In einem weiteren Schritt wurden die Nuten mit Lotmaterial in pastöser Form gefüllt und daraufhin eingebrannt. Eine Herausforderung stellt hierbei das einzusetzende Lotmaterial dar. Gleich mehrere Eigenschaften müssen von diesem erfüllt werden. Das Lot muss für eine Anhaftung die Keramik benetzen, elektrisch widerstandsarm sein, um hohe Leistungsverluste in den Leitern zu verhindern, und in der Lage sein, variable Querschnitte der Leiterbahnen auszubilden. Eine Anhaftung des Lotmaterials an die Keramik kann in Form von Beimischung aktiver Elemente wie z.B. Titan erfolgen, welches beim Einbrennen Sauerstoffbrücken mit der Randfläche der Keramik bildet. Die vorgefertigten Ausbuchtungen im keramischen Grundkörper werden mit Aktivlot gefüllt, welche beim Brennen die eigentliche Leiterbahn bildet. Im vorliegenden Projekt wurden in einen CIM Grundkörper variable Leiterbahnquerschnitte durch Nuten mit unterschiedlichen Querschnitten und Kurvengeometrien mit variablen Radien eingebracht. Die Nuten weisen eine Querschnittsfläche von 0,5 mm², 1,5 mm², und 3 mm³ auf. Die Befüllung der Nuten mit Lotmaterial erfolge durch das Auftragen der Aktivlotpaste mittels eines Dispensers. Alternativ wurden auch zurechtgeschnittene Lotbleche eingesetzt. Der Einsatz der Lotpaste hat sich hierbei jedoch als zielführender herausgestellt. Das Lotmaterial bildet beim Erstarren den eigentlichen Leiter aus. Durch die Beimischung unterschiedlicher Elemente wird es möglich eine Leiterbahn herzustellen, die nur marginal schlechtere Leitungsverlustwerte aufweist, wie ein korrespondierender Kupferleiter. Die Rechnung in Abbildung 2 verdeutlicht dies. Hierbei werden zwei unterschiedlich legierte Aktivlote mit einem konventionellen Kupferleiter gleichen Querschnitts verglichen. In der Rechnung wird die Verlustleitung der Leiter bei Einsatz eines 10 W Verbrauchers bei 0,1 m Leiterlänge und 1,5 mm² Leiterquerschnitt bei Raumtemperatur berechnet. In einem weiteren Schritt wurde die Möglichkeit erforscht, intrinsische Leiterbahnen in der Keramik herzustellen. Dies wird durch feine Bohrungen und Kanäle realisiert, die mit Lotmaterial durch den Kapillareffekt oder Unter- bzw. Überdruck befüllt werden. Abbildung 3 verdeutlicht dies anhand einer Bruchfläche durch eine Ferrule aus Zirkonoxid. Die Mittenbohrung weist einen Durchmesser von 0,1 mm bei einer Länge von 10 mm und einem Gesamtdurchmesser von 2 mm auf. Als Lotmaterial kam ein Standard-Weichlot zum Einsatz, das mittels Unterdruck in die Bohrung gesaugt wurde. Das Ziel ist ein mechanisch und thermisch hoch belastbarer CIM Körper, welcher die notwendige Elektronik zur Funktionserfüllung innerhalb der Struktur vereint. Keramik


[ 77 ] Matuschka, B.; Ruhs, C. & Schulze, V. (2013), "Qualitätssicherung in der Mikrofunkenerosion". Kolloquium Mikroproduktion, eds. Rainer Tutsch (Hrsg.), pp. 14.
Abstract:
Die Qualitätssicherung von Bauteilen in der Mikroproduktion stellt hohe Anforderungen an die eingesetzte Messtechnik dar, da diese über eine sehr hohe Genauigkeit verfügen müssen, um die gefertigten Mikrostrukturen vermessen zu können. Bei der Mikrofunkenerosion ist die Rauheit der Oberfläche ein Indiz für die Qualität der verwendeten Erosionsparameter. Unter Zuhilfenahme der Oberflächenbeschaffenheit, welche ein Bewertungskriterium der verwendeten Erosionsparameter darstellt, wird die gefertigte Geometrie mit einem konfokalen Weißlichtsensor während der Bearbeitung periodisch überprüft und die Erosionsparameter ggf. angepasst. Ziel ist es, eine möglichst genaue Mikrogeometrie gemäß den Vorgaben zu fertigen und diese im laufenden Prozess durch eine automatische Vermessung zu validieren.


[ 78 ] Fleischer, J.; Lanza, G.; Schulze, V.; Sauer, A. & Sell-Le Blanc, F. (2012), "Produktionstechnische Herausforderungen der Elektromobilität". Tagungsband zur wbk-Herbsttagung 2011, eds. Fleischer, J.; Lanza, G. & Schulze, V., Springer VDI Verlag, pp. 16.
Abstract:
Die wbk-Herbsttagung hat sich als wichtigste jährliche Veranstaltung am wbk etabliert. Dieses Jahr fand sie am 27. Oktober 2011 zum Thema „Produktions-technische Herausforderungen der Elektromobilität“ statt. Hintergrund für die Themenwahl ist der Wandel in der Mobilität von rein auf Verbrennung basierten Antriebskonzepten hin zu voll-elektrischen Fahrzeugen und den damit verbundenen Speichertechnologien.


[ 79 ] Kotschenreuther, J.; Delonnoy, L.; Hochrainer, T.; Weber, M.; Schmidt, J.; Fleischer, J.; Schulze, V.; Löhe, D. & Gumbsch, P. (2005), "Modellierung und experimentelle Untersuchungen von Größeneffekten beim Stirndrehen von 90MnCrV8 im vergüteten Zustand". 2. Kolloquium Prozessskalierung, Proceedings, pp. 219-241.
Abstract:
Bei der Miniaturisierung von Zerspanprozessen nimmt die Bedeutung von Effekten, die aufgrund nicht ähnlichkeitsgerecht skalierbarer Größen auftreten, zu. Ein solcher Effekt ist beispielsweise der exponentielle Anstieg der spezifischen Schnittkraft bei Verringerung der Spanungstiefe. ln dieser Arbeit werden diese Größeneffekte anhand des Werkzeugstahls 90MnCrV8 im vergüteten Zustand untersucht. Nach umfangreichen Analysen des Werkstoffes erfolgen anhand von Stirndrehversuchen im Orthogonalschnitt Variationen von Schnitttiefe, Schnittgeschwindigkeit und Schneidkantenverrundung. Schnittkraftmodelle, die bereits aus der Makrozerspanung bekannt sind, werden anschließend mit den Experimenten verg lichen. Mittels dimensionsloser Kennzahlen sollen die Größeneffekte quantifizierbar gemacht werden. Darauf aufbauend fließen diese Erkenntnisse in die Modelle der FEM Simulation ein, um eine genaue Abbildung und damit eine genaue Vorhersagbarkeit des Prozessverhaltens zu erreichen.


[ 80 ] Schulze, V.; Kühnewein, C. & Autenrieth, H. (2011), "3D-FEM Modeling of Gear Skiving to Investigate Kinematics and Chip Formation Mechanisms". Proceedings of the 13th CIRP Conference on Modeling of Machining Operations (CIRP CMMO), eds. Advanced Materials Research, pp. 46-55.
Abstract:
Latest research clearly demonstrates the excellent capability of the gear skiving process. For further improvement of the process and particularly for the enhancement of the process reliability fundamental scientific research is conducted. In this paper the result of investigation of process kinematics and chip formation mechanisms are presented. First the experimental analyses will be described, which represent an essential basis for developing and validating the models. In further experiments the material behavior of the test material SAE 5120 was determined and a material model was developed. The modeling of the process represents a central aspect of the research. This includes the basic modeling of the kinematics in a 3D-model. The simulation enables analysis of the kinematical conditions as well as the chip formation mechanisms and evaluation of the effects on process reliability. The results support the tool and process design and are an important basis for the implementation of the process.


[ 81 ] Autenrieth, H.; Weber, M.; Deuchert, M. & Schulze, V. (2009), "Investigation of the surface characteristics for the micro-cutting process with finite element simulation". Eds. Materials Science Forum 638-642(2010), pp. 2531-2536.
Abstract:
As the service life of components is significantly influenced by the surface layer properties, namely surface roughness, surface work hardening and residual stresses, these are the focus of many investigations. As these properties can be measured experimentally in many cases only after finish of the process, simulation models can be used to explain the final process results by the interpretation of the development of the result quantities during the loading and unloading state. The developed and validated simulation model and the extended process knowledge can be used afterwards to predict process parameter combinations with optimal process results for other cutting tool-workpiece combinations without performing large and costly experimental investigations. In the present study, the dependences of surface work hardening and residual stresses on process parameters of micro-cutting, namely cutting depth, cutting velocity and cutting edge radius are investigated by 2D finite element simulations using ABAQUS/Standard. The material behaviour of normalized AISI 1045 is described in dependence of strain, strain rate, and temperature. Chip formation is modelled by continued remeshing of the work piece. The simulation results are validated by the comparison with experimentally determined integral width and residual stress depth profiles, using x-ray diffraction method. The influence of the ploughing process, characterized by the ratio of cutting edge radius to cutting depth, on surface characteristics is well described by the simulation model.


[ 82 ] Schulze, V.; Haupt, S. & Weber, P. (2008), "Hybrid machining of microstructures using a combination of EDM-milling and laser ablation". XXXX, eds. XXXX, pp. 1-4.
Abstract:
Using laser beam machining with ultrashort laser pulses, microstructures in the micrometer region can be manufactured in virtually all materials, regardless of their mechanical properties. However, machining times are slow if good surface qualities are required. Micro electrical discharge machining (EDM) is also capable of removing material nearly without process forces, but with a higher processing speed if structure sizes exceed a certain value. With the combination of both processes, specific advantages can be realized while disadvantages can be partially eliminated.Therefore, a hybrid machine tool was developed that combines the two processes of ultrashort pulsed laser ablation and EDM milling. No reclamping is necessary. In this study, the limitations and challenges of the single processes are investigated. After that, the novel hybrid machine tool ispresented, along with strategies for the efficient and economic manufacturing of microstructures in materials that are difficult to machine by conventional processes.


[ 83 ] Schulze, V.; Haupt, S. & Weber, P. (2008), "Hybrid machining of microstructures using a combination of electrical discharge machining milling and laser ablation". Pp. 1-4.
Abstract:
Using laser beam machining with ultrashort laser pulses, microstructures in the micrometer region can be manufactured in virtually all materials, regardless of their mechanical properties. However, machining times are slow if good surface qualities are required. Micro electrical discharge machining (EDM) is also capable of removing material nearly without process forces, but with a higher processing speed if structure sizes exceed a certain value. With the combination of both processes, specific advantages can be realized while disadvantages can be partially eliminated. Therefore, a hybrid machine tool was developed that combines the two processes of ultrashort pulsed laser ablation and EDM milling. No reclamping is necessary. In this study, the limitations and challenges of the single processes are investigated. After that, the novel hybrid machine tool is presented, along with strategies for the efficient and economic manufacturing of microstructures in materials that are difficult to machine by conventional processes.


[ 84 ] Gerstenmeyer, M.; Zanger, F. & Schulze, V. (2016), "Complementary Machining – Machining Strategy for Surface Modification". Procedia CIRP 45, eds. Elsevier, pp. 247-250.
Abstract:
In metal production mechanical surface treatments are used to optimize workpiece characteristics like fatigue strength. Complementary Machining is a new machining strategy which is characterized by the combination of cutting and mechanical surface treatment. After cutting the insert is used reversely acting as a tool for mechanical surface treatment. This paper shows the effect of high plastic deformation rates in the surface layer reducing surface roughness and increasing strain hardening. Furthermore, it is supposed that the process induces grain refinement in the surface layer. The process strategy Complementary Machining is investigated during machining Armco-Iron and AISI 4140.


[ 85 ] Lienert, F.; Gerstenmeyer, M.; Krall, S.; Lechner, C.; Trauth, D.; Bleicher, F. & Schulze, V. (2016), "Experimental Study on Comparing Intensities of Burnishing and Machine Hammer Peening Processes". Procedia CIRP 45, eds. Elsevier, pp. 371-374.
Abstract:
Many components in industrial practice need to be finished by surface modification processes in order to assure service properties like fatigue resistance, tribological properties and corrosion resistance. In order to compare the potential of different machine hammer peening (MHP) processes and burnishing Almen strips were treated with three aims: highest deflection, lowest surface roughness and predefined similar process parameters. This paper presents results of the surface layer states, in particular residual stresses, micro hardness and surface roughness in comparison to the deflection of the Almen strips after processing with the above mentioned aims.


[ 86 ] Bollig, P.; Köhler, D.; Zanger, F. & Schulze, V. . (2016), "Effects of different levels of abstraction simulating heat sources in FEM considering drilling". Procedia CIRP, eds. Elsevier, pp. 115-118.
Abstract:
This paper presents a comparison of three different methods of simulating heat sources in 3D-FEM-simulations with various levels of abstraction for drilling. The investigated methods are modelled and evaluated with respect to calculation time and accuracy of simulated temperature fields and phase transformations. Results are showing a significant variance of the maximum temperature and temperature distribution for the three different heat sources although the same amount of energy is used in the simulation model. According to the longest simulation time the most detailed heat source provides a realistic temperature distribution.


[ 87 ] Fleischer, J.; Schulze, V.; Klaiber, M.; Bauer, J.; Zanger, F.; Boev, N.; Leberle, U.; Spohrer, A. & Rothaupt, B. (2016), "The influence of tool holder technologies on milling performance ". Procedia CIRP 46 ( 2016 ), eds. ELSEVIER, pp. 226-229.
Abstract:
The quality of machined surfaces is significantly influenced by machine vibrations caused by the cutting process. Whereas most publications ignore the influence of the tool holder, this paper considers the dynamic behaviour of the whole cutting system consisting of spindle, tool holder, tool and workpiece. Therefore modal and operational vibration analyses were performed to describe the damping and operational characteristics of two competing tool holder technologies, namely heat shrink (HS) and hydraulic expansion (HE). It is shown that HE has higher damping rates than HS. Therefore, HE showed mainly better surface qualities, a 10 % higher productivity and an up to 300 % higher achievable life time of tools.


[ 88 ] Segebade, E.; Zanger, F. & Schulze, V. (2016), "Influence of Different Asymmetrical Cutting Edge Microgeometries on Surface Integrity". Procedia CIRP 45, eds. Elsevier, pp. 11-14.
Abstract:
The importance of cutting edge microgeometries in machining operations has been proven time after time again. Not only with regard to wear, but also as an important factor influencing the resulting surface integrity. In this paper the influence of asymmetric cutting edge microgeometries and different process parameters on the resulting accumulated plastic strain, plastic strain rates and surface layer microstructure of AISI 4140 in cutting experiments and FE-simulations is investigated. To characterize the cutting edge microgeometries a recently published method considering the process parameters such as cutting angles is used.


[ 89 ] Matuschka, B.; Boev, N.; Zanger, F. & Schulze, V. (2016), "Simulation based reduction of the impact load occurring in the moment of cutting edge entrance in order to prolong tool-life". Applied Mechanics and Materials, eds. TPP, pp. 112-118.
Abstract:
High mechanical impact loads in interrupted or inhomogeneous machining processes frequently lead to spontaneous fracture of the cutting edge. Even modern cutting materials cannot provide a combination of hardness and toughness that is capable of preventing this sort of tool failure. Such machining conditions therefore remain difficult, and further investigations aiming to reduce the impact load of the cutting tool in order to enhance tool-life are necessary. A simulation model of the impact situation, that serves to optimize a force conducting structure with regard to elasticity, damping properties and resulting force peaks, was developed and is presented in this paper. Furthermore, measurement devices were composed that are needed for high-resolution recording of impact forces without repercussions and for verification of the elaborated simulation model. It could be shown that mechanical damping of the cutting tool can lead to reduced impact forces on the cutting edge, which in turn should lead to longer tool life.


[ 90 ] Bejnoud, F.; Zanger, F. & Schulze, V. (2016), "Influence of a high speed broaching and case-hardening process on the resulting component geometry". 13th International Conference on High Speed Machining, eds. Tbd., pp. 6.
Abstract:
In this study the effects of a case hardening process on the resulting component geometry considering the pre-process broaching is examined for sliding sleeves made of case hardening steel SAE 5115. The results indicate a significant influence of the initial state of the components on the resulting component contour after heat treatment. Particularly deviations from the ideal contour of the components due to a previous internal soft broaching process with different cutting speeds influence the resulting component contour. Near surface phase transformations during soft broaching at high cutting speeds are identified as a further influence on the resulting component contour.


[ 91 ] Walter, V.; Weidenmann, K. A. & Schulze, V. (2014), "A Comparison of FSW, BHLW and TIG Joints for AL-Si-Mg alloy (EN AW-6082 T6)". Procedia CIRP, eds. XXX, Elsevier, pp. 120-125.
Abstract:
For joining lightweight frame structures, two welding methods are within the focus of the Transregional Collaborative Research Centre SFB/TR 10. The first one is the friction stir welding (FSW) and the second one s the bifocal hybrid laser welding (BHLW). To compare the properties of joints manufactured using these techniques with tungs en inert-gas welding (TIG), representing a conventional joining method, a benchmark was performed. This benchmark includes a comparison of the microstructure, the pore distribution, the microhardness and the mechanical behavior at quasi-static and high-speed tensile loading. The results reveal that the BHLW and the FSW processes outperform the TIG process regarding the mechanic l properties of the joints produced.


[ 92 ] Weingärtner, R.; Hoffmeister, J. & Schulze, V. (2013), "Generation and determination of compressive residual stresses of short penetration depths". Materials Science Forum, eds. S.J.B. Kurz, Trans Tech Publications, Durnten-Zurich, pp. 580-586.
Abstract:
Generating compressive residual stress states with high gradients and low penetration depths offers high capability regarding increase of fatigue limit of parts. In this work the determination of such specific residual stress distributions by using X-ray diffraction and a little material removal is introduced. Measurements are compared using two interference peaks of different penetration depths, at which confocal microscopy enables high accuracy in determination of the step sizes in electrochemical machining. Furthermore the realisation of these states by two different peening processes using micro blasting media is described. The suitability of the processes micro peening and ultrasonic wet peening as surface treatment methods to improve fatigue limit are shown. Micro peening is based on the shot peening principle with small shots and ultrasonic wet peening on the acceleration of small blasting particles by cavitation. The investigations were conducted at AISI 4140 in a quenched and tempered state. Besides the residual stresses and the integral width of interference peaks as well as the depth distributions, the surface topography was examined. The beneficial effects of these conditions on the fatigue limit in bending tests are described.


[ 93 ] Benes, P.; Hoffmeister, J.; Schulze, V. & Bechle, A. (2012), "Finite-element-analysis of the forming process cross rolling with the aim of exploring the material flow and the damage degree in work pieces". XXX, eds. XXX, pp. 999.
Abstract:
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[ 94 ] Benes, P.; Hoffmeister, J.; Schulze, V. & Selten, M. (2013), "Finite-Elemente-Analyse des Prozesses Profil-Querwalzen zur Beschreibung des Materialfließens und des Versagensmechanismus im Verzahnungsinneren". XXX, eds. XXX, pp. 999.
Abstract:
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[ 95 ] Gerstenmeyer, M.; Segebade, E.; Zanger, F. & Schulze, V. (2017), "Simulation der mechanischen Oberflächenbehandlung mit Simufact Forming". 18. Roundtable Simulating Manufacturing, eds. Dr. Hendrik Schafstall und Michael Wohlmuth, pp. 180-189.
Abstract:
Zur spanenden Herstellung metallischer Bauteile sind mehrere Prozessschritte erforderlich. Diese sind bspw. ausgehend vom Halbzeug über Schrupp-Schlicht-Strategien bis hin zum Surface- Finishing. Bei der Schrupp-Schlicht-Strategie folgt einer Zerspanung mit vergleichsweise hohen Schnitttiefen eine Endbearbeitung mit weitaus geringerer Schnitttiefe und angepassten Prozessparametern. Eine Möglichkeit zum Surface-Finishing ist die sog. Komplementärzerspanung. Dabei erfolgt nachfolgend zur Zerspanung eine mechanische Oberflächenflächenbehandlung mit dem eigentlichen Schneidwerkzeug. Charakteristisch ist, dass die Bearbeitungsrichtungen von Zerspanung und Oberflächenbehandlung entgegengesetzt erfolgen. Jeder dieser Prozessschritte beeinflusst die Bauteilzustände in der Randschicht. Die simulative Betrachtung von vorhergehenden Prozessen und der damit einhergehenden Änderung der Randschichtzustände ist für das Prozessverständnis ein elementarer Bestandteil, um optimale Bearbeitungsergebnisse und damit Bauteileigenschaften zu erhalten. Neben der reinen Beschreibung der Fertigungsprozesse muss für eine ganzheitliche Prozessbeschreibung auch das elasto-plastische Materialverhalten mittels geeigneter Materialmodelle beschrieben werden. In dieser Arbeit werden aufbauend auf 2D- und 3D-Spanbildungssimulationen in Simufact Forming eine Mehrfachzerspanung (Schrupp-Schlicht- Strategie) sowie die Komplementärzerspanung vorgestellt. Neben der Betrachtung der Schneidkantenmikrogeometrie stehen auch die resultierenden Randschichtzustände im Mittelpunkt der Untersuchungen.


[ 96 ] Segebade, E.; Gerstenmeyer, M.; Zanger, F. & Schulze, V. (2017), "Zerspanungssimulation mit Simufact Forming". 18. Roundtable Simulating Manufacturing, eds. Dr. Hendrik Schafstall und Michael Wohlmuth, pp. 116-127.
Abstract:
Spanbildungsvorgänge an metallischen Bauteilen, wie beispielsweise der Drehprozess, sind gekennzeichnet durch ein thermo-mechanisches Lastkollektiv, welches während des Prozesses auf die der Schneidkante sowie auf das Bauteil und den Span einwirkt. Der Einfluss hoher Temperaturen, Dehnraten und Dehnungen müssen für Werkstoffe charakterisiert werden, um in der Simulation ein realistisches Materialverhalten abzubilden. Dabei stellen auch unsichere Kenntnisse über die Reibungsverhältnisse im realen Prozess eine Herausforderung für die Modellierung dar. Hinzu kommt die Notwendigkeit einer stabilen und effizienten Neuvernetzungs- oder Trennungsroutine zur Realisierung der Spanbildung. Für die Simulation spanabhebender Fertigungsprozesse haben sich aufgrund dieser Umstände in den letzten Jahren geeignete Softwarepaketen international etabliert. Die Eignung der Software Simufact Forming wurde im Rahmen aktueller Arbeiten sowohl für 2D- als auch für 3D-Spanbildungssimulationen demonstriert und anhand von experimentell ermittelten Kräften validiert. Dabei fand auch die Schneidkantenmikrogeometrie Beachtung. Die Mikrogeometrie nimmt nachweislich Einfluss auf die Prozesskräfte sowie die zerspanungsbedingten Randzonenzustände, wie die Gefügestruktur und Eigenspannungsverteilung.


[ 97 ] Gerstenmeyer, M.; Ort, B.; Zanger, F. & Schulze, V. (2017), "Influence of the cutting edge microgeometry on the surface integrity during mechanical surface modification by Complementary Machining". Procedia CIRP, eds. Elsevier, pp. 55-60.
Abstract:
In metal production, mechanical surface modifications are used to optimize workpiece characteristics to improve properties such as fatigue strength. Machining and mechanical surface modification can be integrated in the process strategy Complementary Machining. After machining the cutting tool is used reversely acting as a tool for mechanical surface modification. This paper shows the influence of the cutting edge microgeometry on process forces and temperatures as well as process induced grain refinement in the surface layer during the mechanical surface modification of Armco-Iron and AISI 4140. The mechanical surface modification is simulated in a 3D-FEM-simulation with ABAQUS/Standard.


[ 98 ] Segebade, E.; Gerstenmeyer, M.; Zanger, F. & Schulze, V. (2017), "Cutting Simulations Using a Commercially Available 2D/3D FEM Software for Forming". Procedia CIRP, eds. Elsevier, pp. 73-78.
Abstract:
Chip formation simulations require either sophisticated material based element removal or deactivation routines, or a powerful remeshing procedure. Therefore the accuracy of all chip formation simulations significantly depends on the FEM-software as well as the material data. Over the course of the past years, a few select commercial programs became the pre-eminent choice for chip formation simulations. In this work, the software simufact.forming, which is not one of those few programs widely in use, has been employed for 2D and 3D chip formation simulations. Orthogonal cutting experiments with AISI4140 were conducted and subsequently modeled, including the cutting edge radius. The results were analyzed with regard to how well chip formation and the resulting process forces in 2D and 3D can be depicted.


[ 99 ] Zanger, F.; Sellmeier, V.; Klose, J.; Bartkowiak, M. & Schulze, V. (2017), "Comparison of Modeling Methods to Determine Cutting Tool Profile for Conventional and Synchronized Whirling". Procedia Cirp, eds. Elsevier, pp. 222-227.
Abstract:
The determination of cutting tool profiles for machining operations with coupled rotational kinematics like gear and screw generation can be a complex task which is executed by either numerical or analytical methods. The cutting tool profile for whirling is derived from process parameters and desired workpiece geometry by both a numerical dexel-based model and an analytical model based on the condition of tangential motion. The models are adapted to a process variant of whirling with synchronized rotation of tool and workpiece and compared regarding accuracy, computation time and geometrical flexibility.


[ 100 ] Klotz, S.; Klose, J.; Sellmeier, V. & Schulze, V. (2017), "Variantenanalyse zur Effizienzsteigerung beim Wirbeln mit synchronem Drehen". PIA - Prozessketten im Automobilbau, eds. Denkena, B., pp. 121-129.
Abstract:
PIA - Prozesskette im Automobilbau, Tagung bei DMG Mori in Bielefeld vom 03. – 04.07.2017, Vorstellung des Themas "Variantenanalyse zur Effizienzsteigerung beim Wirbeln mit synchronem Drehen".


[ 101 ] Imbrogno, S.; Segebade, E.; Fellmeth, A.; Gerstenmeyer, M.; Zanger, F.; Schulze, V. & Umbrello, D. (2017), "Microstructural and hardness changes in aluminum alloy Al-7075: Correlating machining and equal channel angular pressing". AIP Converence Proceedings 1896, eds. American Institute of Physics, pp. 1-6.
Abstract:
Recently, the study and understanding of surface integrity of various materials after machining is becoming one of the interpretative keys to quantify a product´s quality and life cycle performance. The possibility to provide fundamental details about the mechanical response and the behavior of the affected material layers caused by thermo-mechanical loads resulting from machining operations can help the designer to produce parts with superior quality. The aim of this work is to study the experimental outcomes obtained from orthogonal cutting tests and a Severe Plastic Deformation (SPD) process known as Equal Channel Angular Pressing (ECAP) in order to find possible links regarding induced microstructural and hardness changes between machined surface layer and SPD-bulk material for Al7075. This scientific Investigation aims to establish the basis for an innovative method to study and quantify metallurgical phenomena that occur beneath the machined surface of bulk material.


[ 102 ] Götze, E.; Zanger, F. & Schulze, V. (2017), "Finish machining of laser beam melted parts". Proceedings of the Special Interest Group meeting on Dimensional Accuracy and Surface Finish in Additive Manufacturing, eds. Euspen Headquarters, pp. 99-103.
Abstract:
The finish machining process of parts manufactured by laser beam melting is of high concern due to the lack of surface accuracy. Therefore, the focus of the work lies on the influence of the build-up direction of the parts and their effect on the finish machining process. The investigated process is drilling with a drill diameter of 6.8 mm and a drilling depth of 30 mm using lubrication. The investigations contain the materials stainless steel (1.4404), titanium (Ti6Al4V) and nickel-base alloy (IN718). Due to the difficulties of machining of nickel-base alloys a cemented carbide drill with a special nitride based coating is utilized for IN718. For the material Ti6Al4V and 1.4404 a cemented carbide drill with a TiAlN coating is chosen. During the experiments the feed rate was varied in the range of 0.1 mm/rev and 0.2 mm/rev. Additionally, the selection of the cutting speed varies for the different materials. For 1.4404 cutting speeds between 60 m/min and 100 m/min were chosen, for IN718 and Ti6Al4V more moderate cutting speeds between 25 m/min and 55 m/min were selected. The results provide the base for processing strategies. Therefore, the specimens are solely laser beam melted without post-processing like heat treatment. During the experiments the drilling forces and the resulting roughnesses are evaluated.


[ 103 ] Fellmeth, A.; Zanger, F. & Schulze, V. (2017), "Kinematic Hardening of AISI 5120 During Machining Operations". Procedia Cirp 58, eds. Elsevier, S., pp. 104-109.
Abstract:
Metal manufacturing processes like machining include complicated load cases and significant plastic deformation inside the manufactured component. The Finite-Element-Method (FEM) has been successfully applied to analyze machining processes. The plastic deformations during machining operations, especially of ductile materials, are a major part of the total deformation. If the deformation incorporates a large plastic deformation part with changing spatial directions, kinematic hardening should be considered, additionally to isotropic hardening. Previous work on the kinematic hardening of ARMCO iron revealed an almost near constant ratio of isotropic and kinematic hardening. The constant kinematic hardening ratio is revised and analyzed in tensile-compression tests with normalized AISI 5120. The FEM simulation results using the new material model of the kinematically hardening AISI 5120 are validated with experimental force measurement during orthogonal machining. The influence of kinematic hardening during machining operations is not the major influence, but still substantial.


[ 104 ] Helfrich, A.; Klotz, S.; Zanger, F. & Schulze, V. (2017), "Machinability of Continuous-Discontinuous Long Fiber Reinforced Polymer Structures". Procedia CIRP, eds. Elsevier, pp. 193-198.
Abstract:
In the present paper a new material system which combines the properties of continuous and discontinuous fibers (CoDiCoFRP) is investigated. The machinability and the induced damage effects of six material variations are investigated for a milling process at various cutting speeds and feed rates with an uncoated cemented carbide tool. The resulting forces and cutting torque were measured and analyzed for each material. After the milling process, the surface layers of the specimens were analyzed to quantify damage introduced during the milling process. The results show a strong influence of the material structure on the machining forces and damage.


[ 105 ] Gabsch, A.; Klotz, S.; Zanger, F. & Schulze, V. (2017), "Dynamische Parameteranpassung bei der Mikrozerspanung von 20MnCr5". 8. Kolloquium Mikroproduktion, eds. F. Vollertsen, J. W., pp. 149-154.
Abstract:
Im Rahmen der vorliegenden Untersuchungen wurde trotz Verschleißes das reale Eingriffsverhältnis, definiert durch den Quotienten aus modifiziertem Schneidkantenabschnitt an der Spanfläche zu Schnitttiefe Sγ‘/ap, durch Anpassen der Vorschubgeschwindigkeit beim Längs-Plandrehen konstant gehalten. Der Quotient von Sγ‘/ap wurde in den Versuchsreihen auf verschiedene Werte festgelegt, um so das beste Verhältnis zu identifizieren. Der untersuchte Werkstoff war 20MnCr5 im weichgeglühten Zustand. Die Schneidkante wurde in einem Intervall von 100 m Standweg mit Hilfe eines taktilen Messsystems gemessen. Anschließend wurde die Vorschubgeschwindigkeit und damit die Schnitttiefe an den aktuellen Verschleißzustand des Werkzeuges derart angepasst, dass der Quotient von Sγ‘/ap während der weiteren Versuche konstant blieb. Die Untersuchungen haben gezeigt, dass bei richtiger Wahl des Verhältnisses von Sγ‘/ap, eine deutliche Verringerung des Spanflächenverschleißes gegenüber der Referenzbearbeitung möglich ist.


[ 106 ] Götze, E.; Heinzel, Y.; Matuschka, B.; Zanger, F.; Schulze, V.; Rohde, M.; Krügelstein, A. & Franke, J. (2017), "Optimierung der Aktivlotzusammensetzung für Al2O3 und Herstellung von innenliegenden Leiterbahnen". 8. Kolloquium Mikroproduktion, eds. F. Vollertsen, J. W., pp. 129-134.
Abstract:
Aluminiumoxidkeramik ist aufgrund des kostengünstigen Anschaffungspreises und des vielfältigen Einsatzgebietes die beliebteste Keramik. Aufgrund der stetigen Bauteilverkleinerung in mechatronischen Systemen, wie sie beispielsweise in der Automobilindustrie oder der Medizintechnik eingesetzt werden, werden einerseits die Herstellung von innenliegenden Strukturen und andererseits die elektrische Funktionalisierung der geschaffenen Grundkörper erforderlich. Für die Herstellung von Grundkörpern mit innenliegenden Leiterbahnen wurde konventionelles 96,0%-Al2O3 eingesetzt sowie LithaLox HP 500 der Firma Lithoz für die Fertigung von additiv aufgebauten Bauteilen. Die Konstruktion der Bauteile sowohl für die konventionelle als auch additive Fertigung enthält Grabenstrukturen unterschiedlicher Breite (0,05 mm – 4 mm) und Tiefe (0,05 mm – 1 mm). In einem anschließenden Fügeprozess mit einer ebenen Keramik entstehen aus diesen Gräben innenliegende Strukturen entstehen. Ein weiterer Fokus lag auf der Zusammensetzung einer Aktivlotlegierung aus Titan (3 - 5 Gew.-%), Silber und Kupfer, die sich aufgrund ihres geringen elektrischen Widerstands auszeichnet und somit als Leiterbahn eignet. Es wurden Pasten unterschiedlicher Zusammensetzung hergestellt, aufgetragen und thermisch mit der Keramik gefügt. Anschließend wurden Schliffe unter dem Licht- und Rasterelektronenmikroskop untersucht und einerseits die Titanausfällungen und anderseits die Anbindung an die Keramik bewertet.


[ 107 ] Segebade, E.; Klose, J.; Gerstenmeyer, M.; Zanger, F. & Schulze, V. (2017), "Mechanical surface modification using cutting inserts". Proceedings of the 13th ICSP, eds. International Scientific Committee for Shot Peening, pp. 219-224.
Abstract:
The objective of this work is presenting the foundation of a true integration of mechanical surface modification and machining. This “fusion” entails mechanical surface modification parallel to the cutting process using the cutting insert as tool. While it may seem, that something similar can be achieved through classical vibration assisted machining (VAM), this is definitely not the case. The resulting relative velocity between cutting insert and workpiece will ensure the process to be firmly rooted in cutting rather than hammering of the workpiece. Since creating a setup suitable to address this issue is a big challenge in itself, it is prudent begin by establishing the general feasibility of the process. The first priority is therefore proving that cutting inserts can be used to induce surface layer states similar to those achieved by MHP-processes. The presented work addresses this validation of mechanical surface treatment using cutting inserts regarding topography, residual stresses and work hardening by model experiment.


[ 108 ] Zanger, F.; Bollig, P. & Schulze, V. (2017), "Simulative investigations on different friction coefficient models". Procedia CIRP, eds. Elsevier, pp. 140-145.
Abstract:
This work aims on the comparison of different friction coefficient models depending on the variable parameters including sliding speed, temperature, contact pressure based on experimental friction measurements. The impact on the temperature distribution to predict phase transformations during turning of AISI 4140 for dry and minimum quantity lubricated machining is investigated for each parameter separately. Based on these results an optimized friction model is built up. The results are validated with experiments.


[ 109 ] Gerstenmeyer, M.; Segebade, E.; Fedder, G.; Zanger, F. & Schulze, V. (2018), "Prozesskettensimulation: Additive Fertigung und spanende Nachbearbeitung". 19. RoundTable Simulating Manufacturing, eds. Dr. Hendrik Schafstall und Michael Wohlmuth, H., pp. 32-45.
Abstract:
Nach der additiven Fertigung ist in der Regel ein Zerspanungsschritt an technischen Oberflächen des Bauteils erforderlich, um den Anforderungen an die Oberflächenqualität gerecht zu werden. Zur Sicherstellung dieser Anforderungen kommt zunehmend die simulative Betrachtung von additiven aber auch Zerspanungsprozessen zum Einsatz. Damit einhergehend können insbesondere bei kostenintensiven Prozessen, wie der additiven Fertigung, experimentelle Prozessauslegungen reduziert werden. Für ein ganzheitliches Prozess¬verständnis der Zerspanung ist weiterhin die Betrachtung der vorhergehenden Prozesse und der damit einhergehenden Änderung der Randschichtzustände ein elementarer Bestandteil. In dieser Arbeit wird der additive Herstellungsprozess eines Bauteils aus AlSi10Mg mit Simufact Additive betrachtet. Für die anschließende simulative Betrachtung der Zerspanung werden die resultierenden Bauteilzustände in Simufact Forming importiert. Bei der Spanbildungssimulation muss neben der reinen Beschreibung des Fertigungsprozesses für eine Prozessbeschreibung auch das elasto-plastische Materialverhalten mittels eines geeigneten Materialmodells beschrieben werden. Die simulativen Analysen werden mit experimentellen Untersuchungen hinsichtlich der wirkenden Prozesskräfte während der Zerspanung analysiert. Abschließend werden diese Ergebnisse mit der Zerspanung von konventionell hergestelltem AlSi10Mg verglichen.


[ 110 ] Kacaras, A.; Gibmeier, J.; Zanger, F. & Schulze, V. (2018), "Influence of rotational speed on surface states after stream finishing". 4th CIRP Conference on Surface Integrity, eds. Procedia CIRP, pp. 221-226.
Abstract:
The stream finishing process proved to be an efficient production process for mechanical surface modification. In particular the rotational speed of a bowl containing the media represents an effective process variable for increasing relative velocity between workpiece and media. Increased work hardening effects and induced compressive residual stresses in the near surface region are expected. In this work the temporal influence of the rotational speed of the bowl on work hardening, residual stresses and surface topography are investigated on quenched and tempered AISI4140 plane specimen with the aim of determining the optimal processing time for surface modification. Furthermore, it is investigated whether grain refinement occurs during stream finishing. A modified Almen system is used as an efficient method for characterizing changes in residual stresses and surface topography during stream finishing. While depth ranges of residual stresses and work hardening showed to be affected by the rotational speed of the bowl and the processing time during stream finishing, residual stress states at the surface showed to be invariant. Increased process efficiency can be obtained by stream finishing using high rotational speed yielding higher depths of induced compressive residual stresses and work hardening in the near surface region in a shorter processing time.


[ 111 ] Zanger, F.; Kacaras, A.; Bächle, M.; Schwabe, M.; Puente Léon, F. & Schulze, V. (2018), "FEM simulation and acoustic emission based characterization of chip segmentation frequency in machining of Ti-6Al-4V". 51st CIRP Conference on Manufacturing Systems, eds. Procedia CIRP, pp. 1421-1426.
Abstract:
FEM chip formation simulations and machining tests of orthogonal cutting were undertaken in order to investigate the influence of cutting speed and tool wear on cutting force, chip segmentation frequency, and residual stress state for Ti-6Al-4V. In addition, acoustic emissions, measured by a piezoelectric sensor adapted to the tool shank, were analyzed to extract chip segmentation frequency in-process using time-frequency representations and periodograms. Results show the capability of robust chip segmentation frequency measuring. The hypothesis of compensating the negative effect of tool wear on the component’s residual stress state by means of targeted adjustment of process parameters can be derived.


[ 112 ] Segebade, E.; Schneider, J. & Schulze, V. (2018), "Tribological Effects in and by Metal Cutting". Tribology in Manufacturing Processes and Joining by Plastic Deformation II, eds. Key Engineering Materials, S., pp. 4-24.
Abstract:
In metal cutting, a severe thermo-mechanical load collective determines the friction and wear behavior at the tool-chip interface. The inaccessibility of this interface complicates studies and thus the understanding of tribological effects in metal cutting. During a tool’s lifetime, local friction conditions change drastically as coatings and tool geometry wear down. This paper shall provide a comprehensive overview of current methods to understand and describe friction conditions in metal cutting and how cutting induced surface layer states may influence the friction and wear behavior of the finished workpiece.


[ 113 ] Segebade, E.; Kümmel, D.; Zanger, F.; Schneider, J. & Schulze, V. (2018), "Influence of cutting edge asymmetry on grain refinement of Ti6Al4V". Procedia CIRP 71, eds. Elsevier LTd., pp. 232-237.
Abstract:
Asymmetrical cutting edges have been proven to influence the resulting surface layer states of machined metal parts. As machining of Ti6Al4V alloy is subject to rather high tool wear, tool geometry changes during machining can influence the resulting surface layer states like residual stresses and nanocrystalline surface layer depth. In this paper, the influence of asymmetric cutting edge microgeometries (characterized by form-factor) and different process parameters on the resulting surface layer microstructure of Ti6Al4V is investigated through face turning experiments and focused ion beam analyses. 2D-FE simulations are conducted using the software Simufact Forming, and a Johnson-Cook model with triaxiality based damage criterion. According to the known mechanisms of grain refinement, mechanical and thermal states are analyzed and related to the experimental data. Relative roundness higher than one, and form-factors smaller than one lead to severe surface layer deformation and increased recrystallization depths, with the effect of form-factor clearly dominating compared to relative roundness.


[ 114 ] Götze, E.; Postler, K.; Buschulte, S.; Zanger, F. & Schulze, V. (2018), "Limits of additively produced alumina substrates for 3D-MID applications". xxx, eds. IEEE, pp. 15-20.
Abstract:
The range of applications for 3D-MID technology is currently limited by the use of thermoplastic basic substrates and restricted design freedom resulting from injection molding. These restrictions are to be overcome by replacing the thermoplastic basic substrate with alumina ceramics on the one hand and by using additive manufacturing on the other hand. The replacement of the thermoplastic basic substrates allows a higher thermal load on the component and paves the way for the use of high-performance electronics with corresponding development of waste heat. The use of additive manufacturing should significantly increase the freedom of design of the basic substrate. Despite all the obvious advantages of additive manufacturing using stereolithography, however, there are design limitations. Thus, the remaining adhesion of slurry to the component leads to a reduction in the possible aspect ratio of the holes, e.g., which are to be used for the electrical through-plating of the ceramic. In addition, the paper deals with the bending strengths achievable by this process-material combination.


[ 115 ] Götze, E.; Zanger, F. & Schulze, V. (2018), "Orthogonal Cutting of Laser Beam Melted Parts". AIP Conference Proceedings, eds. AIP Publishing, pp. 15-20.
Abstract:
The finishing process of parts manufactured by laser beam melting is of high concern due to the lack of surface accuracy. Therefore, the focus of this work lies on the influence of the build-up direction of the parts and their effect on the finishing process. The orthogonal cutting reveals findings in the fields of chip formation, involved forces and temperatures appearing during machining. In the investigations, the cutting depth was varied between 0.05 and 0.15 mm representing a finishing process and the cutting velocity ranges from 30 to 200 m/min depending on the material. The experiments contain the materials stainless steel (AISI 316L), titanium (Ti6Al4V) and nickel-base alloy (IN718). The two materials named latter are of high interest in the aerospace sector and at the same time titanium is used in the medical field due to its biocompatibility. For the materials IN718 and Ti6Al4V a negative rake angle of -7.5° and for stainless steel a rake angle of 12.5° are chosen for the cutting experiments. The results provide the base for processing strategies. Therefore, the specimens were solely laser beam melted without post-processing like heat treatment. The evaluation of the experiments shows that an increase in cutting speed has different effects depending on the material. For stainless steel the measured forces regarding the machining direction to the layers approach the same values. In contrast, the influence of the layers regarding the forces appearing during orthogonal cutting of the materials IN718 and Ti6Al4V differ for lower cutting speeds.


[ 116 ] Segebade, E.; Gerstenmeyer, M.; Zanger, F. & Schulze, V. (2018), "Surface Layer States after Manufacturing Processes - Generation and Evaluation". Efficiency, Flexibility, Integration - Wiener Produktionstechnik Kongress 2018, eds. Bleicher, F., pp. 113-118.
Abstract:
The sum of thermo-mechanical loads during manufacturing of metallic parts across process chains defines surface layer states like topography, work hardening state, residual stresses and microstructure evolution. Single processes along the chain influence the final surface layer states depending on their severity and/or position within the process chain. Simulation-based optimization of processes which are applied to nearly finished products can greatly enhance features like wear resistance or fatigue strength. This paper outlines the influence of mechanical finishing on resulting surface layer states. This includes analyses of machined surfaces produced by scientific orthogonal cutting, as well as industrial operations like machining and mechanical surface treatment or combinations thereof.


[ 117 ] Segebade, E.; Kümmel, D.; Zanger, F.; Schneider, J. & Schulze, V. (2018), "Surface texturing of TiAl6V4 using cutting tools in reverse". Procedia Manufacturing, eds. Elsevier, pp. 97-103.
Abstract:
The usability of Ti-alloys in tribological systems is limited due to high wear rates during sliding. Therefore, many parts of critical aircraft assemblies are built using steel instead. Empowering Ti-alloys to be used in tribological systems will therefore enable a significant reduction of weight in e.g. landing gears. Surface texturing is widely used to improve the tribological behavior of metal parts. Most texturing methods using cutting tools depend on chip formation as the primary mechanism of texturing. In this work, a chipless process of surface texturing titanium parts using a cutting tool is developed. To this end, the resulting texture geometry variance is analyzed regarding the process parameters. It could be demonstrated in selected tribological experiments, that the textured surfaces produced using the chipless process are far superior to textures produced by chip formation.


[ 118 ] Stampfer, B.; Zanger, F. & Schulze, V. (2018), "In-Process Analysis of Minimum Quantity Lubrication during Drilling of AISI 4140". Advances in Production Research, eds. Schmitt, R. & Schuh, G., pp. 541-550.
Abstract:
Minimum quantity lubrication (MQL) is an established concept to meet high ecological and economical demands in metal machining. Compared to flood cooling, MQL massively reduces the efforts associated with the supply and disposal of the lubricants and the handling of emulsion contaminated chips. At the same time, MQL can reach a similar tool life. The mechanisms that have an influence on this effect are a matter of ongoing research. For this work, aerosol was generated by a 1-channel MQL system and supplied to a drilling process with AISI 4140 specimen. The drilling torque, feed force and workpiece temperatures are evaluated under different MQL air input pressures and tool cooling channel lengths. The results are interpreted by the help of flood cooling reference tests and high speed camera recordings, which reveal the open-jet atomisation of lubrication ligaments at the tool exit, arising from different MQL operation parameters.


[ 119 ] Kacaras, A.; Bächle, M.; Schwabe, M.; Zanger, F.; Puente León, F. & Schulze, V. (2019), "Acoustic emission-based characterization of focal position during ultra-short pulse laser ablation". Procedia CIRP, eds. Elsevier, pp. 270-275.
Abstract:
Microstructures were ablated using an ultra-short pulse laser system in order to investigate the influence of focal position on the surface topography. In addition, acoustic emissions measured by a piezoelectric sensor adapted to the AISI 4140 workpiece were analyzed and correlated with the focal position and the resulting surface topography. Frequency ranges sensitive to variations of the z-axis position were determined by STFT analysis. Subsequently, significant signal components were processed to enable an inference about the focal position. The hypothesis of assessing the focal position in-process based on acoustic emissions to ensure high precision during laser ablation could be confirmed.


[ 120 ] González Fernández, G.; Segebade, E.; Zanger, F. & Schulze, V. (2019), "FEM-based comparison of models to predict dynamic recrystallization during orthogonal cutting of AISI 4140". Procedia CIRP 82, eds. Elsevier B.V., pp. 154-159.
Abstract:
Machining processes induce a thermo-mechanical load collective on the surface layer, which leads to grain refinement of varying depths depending on several factors apart from the workpiece. The size relation of the cutting edge radius to the cutting depth (relative roundness) as well as the cutting edge microgeometry influence the generation of nanocrystalline layers. In this work several models to predict dynamic recrystallization during orthogonal cutting of AISI 4140 are compared using 2D FEM-models considering both, relative roundness and cutting edge microgeometry.


[ 121 ] Segebade, E.; Gerstenmeyer, M.; Dietrich, S.; Zanger, F. & Schulze, V. (2019), "Influence of anisotropy of additively manufactured AlSi10Mg parts on chip formation during orthogonal cutting". Procedia CIRP 82, eds. Elsevier B.V, pp. 113-118.
Abstract:
Anisotropic behavior of metals can influence manufacturing processes including acting thermo-mechanical loads and resulting surface layer states. In additive manufacturing, the build-up direction influences material states like microstructure, density distribution and stress fields, possibly leading to anisotropic behavior. In this work, additively manufactured AlSi10Mg is characterized in tension tests in order to determine the anisotropic material deformation behavior due to the build-up procedure. This was implemented in 2D cutting simulations using finite element method. Additionally, orthogonal cutting experiments were performed in order to determine process forces and chip formation, which finally were used in order to validate simulations.


[ 122 ] Vargas, B.; Zapf, M.; Klose, J.; Zanger, F. & Schulze, V. (2019), "Numerical Modelling of Cutting Forces in Gear Skiving". Procedia CIRP 82, eds. Elsevier B.V., pp. 455-460.
Abstract:
Gear skiving is a high-performance machining process for gear manufacturing. Due to its complex kinematics, the local cutting conditions vary during tool engagement. Particularly, the local rake angle can reach highly negative values, which have a significant effect on the cutting force. In this paper, the Kienzle force model with additional coefficients was implemented in a numerical model to calculate local cutting forces considering the influence of local rake angle. The experimental validation based on total cutting forces shows good results and indicates an increase of model accuracy for a wide parameter range by considering the rake angle Variation.


[ 123 ] Vargas, B.; Klose, J.; Zanger, F. & Schulze, V. (2019), "Simulative and Experimental Investigation of Gear Skiving with Reduced Axis Crossing Angles ". GETPRO, eds. Forschungsvereinigung Antriebstechnik e.V. (FVA), pp. 235-244.
Abstract:
Gear skiving has been increasingly used in the production of internal gears and shows high potential to manufacture external gears with adjacent shoulders. In order to avoid tool – workpiece collision, it is possible to minimize the length of tool overrun by reducing the axis crossing angle. However, the process kinematics changes with this reduction, representing a big challenge to the process design. In order to fulfill the lack of detailed knowledge and establish its industrial practice, simulative and experimental studies with axis crossing angles Σ between 5° and 15° were conducted. A three-dimensional kinematic simulation of gear skiving based on penetration calculation was carried out to demonstrate the influence of the process parameters on the local cutting conditions. The results show that the local rake angle reaches extremely negative values at the tooth tip of the cutting tool, which is usually characterized by the highest wear rates and therefore is critical for tool life. In order to relieve the local rake angles inherent to the unfavorable kinematics, both the tool geometry and the process can be optimized. Therefore, the simulations demonstrate how the constructional rake angle and the multiple infeed strategy can positively influence the local rake angle. In order to investigate how the local cutting conditions influence the cutting forces, wear behavior and tool life, tests with single-toothed tools were conducted for different axis crossing angles. The influence of the infeed strategy, tool rake angle and maximum uncut chip thickness on the local cutting conditions were investigated and different wear behaviors for axis crossing angles less than 10° were observed, suggesting a process limit regarding tool life. For smaller angles, the influence of the investigated parameters is very pronounced and the process design is limited to a narrow but still existing parameter window.


[ 124 ] Fleischer, J.; Lanza, G. & Schulze, V. (2019), "Auf dem Weg zur Elektromobilität – Wettbewerbsfaktor Produktionstechnik". Auf dem Weg zur Elektromobilität – Wettbewerbsfaktor Produktionstechnik, eds. Fleischer, J.; Lanza, G.; Schulze, V. & , ., pp. 1-132.
Abstract:
Die Automobilindustrie steckt in einem Transformationsprozess ungeahnten Ausmaßes und Ausgangs. Ob durch striktere europäische Abgasgrenzwerte, den Zwang lokaler Emissionsfreiheit oder den Druck des chinesischen Marktes beim Kampf um eine neue Vor-herrschaftsrolle - die Gründe deutscher Automobilisten zur Elektrifizierung sind vielschichtig und die Folgen kaum abschätzbar. Die Frage, ob neue Antriebstechnologien in den Markt eingeführt werden, stellt sich mittlerweile kein Automobilhersteller mehr, stattdessen verbleibt die Frage nach dem „wie“. Mit der diesjährigen wbk Herbsttagung „Auf dem Weg zur Elektromobilität – Wettbewerbsfaktor Produktionstechnik“ wollen wir die vorhandenen Chancen im Bereich der Produktionstechnik für die Elektromobilität aufzeigen und einen Beitrag dazu leisten, dass diese auch genutzt werden. Hochkarätige Impulsvorträge aus Industrie und Forschung schaffen die Diskussionsbasis für einen Informationsaustausch zur Elektromobilität. Die wbk-Herbsttagung bietet dabei eine Plattform für den Dialog zwischen Politik, Anwendern, Produzenten, Anlagenbauern sowie dem wbk als Forschungspartner vor Ort.


[ 125 ] Stampfer, B.; Golda, P.; Zanger, F.; Schießl, R.; Maas, U. & Schulze, V. (2019), "Thermomechanically coupled numerical simulation of cryogenic orthogonal cutting". 17th CIRP Conference on Modelling of Machining Operations (17th CIRP CMMO), eds. Ozturk, E.; Mcleay, T. & Msaoubi, R., pp. 438-443.
Abstract:
During machining of Ti-6Al-4V, high thermal loads arise, which demand for advanced cooling concepts, such as the application of liquid nitrogen. An efficient approach to analyze the thermomechanical mechanisms which influence the tool life and the workpiece distortions is the usage of coupled numerical simulations. In this work, the Finite -Element-Method was used to simulate the tool-workpiece-interaction and the chip formation, whereas the detailed treatment of the nitrogen fluid flow and its heat transfer is solved by an in-house program using the Finite-Difference-Method. Both simulations are coupled by appropriate boundary conditions, which are updated iteratively during the calculation.


[ 126 ] Zapf, M.; Klose, J.; Zanger, F. & Schulze, V. (2019), "Process forces and surface topography when manufacturing case-hardened gears by double flanked hard skiving". VDI Berichte 2355, eds. VDI Wissensforum GmbH, pp. 1647-1658.
Abstract:
Due to its kinematics, gear skiving offers high potential for hard finish machining of internal and external gears to substitute gear grinding. Single flanked hard machining by skiving offers stable processes, because there’s only one flank in contact during cutting, but is much less productive than double flanked machining. Double flank hard finish machining is highly productive when finishing in one process step. The complex kinematics of skiving are characterized by their asymmetric chip formation due to an irregular cutting thickness of the leading and trailing flank. In this work the influence of process parameters such as cutting velocity, axial feed and radial feed of the finishing cut on the cutting forces, the resulting gear quality, flank surface quality and chip formation is investigated. The parameter studies are carried out in an analogy process using coated cemented carbide inserts with 3 cutters. Validation of the analogy process is provided by experiments with fully toothed tools. In-process force measurements supports the accurate analysis of wear mechanisms of the cemented carbide tools and the chip formation. Process forces are high due to the hardness of the workpiece and rise with the specific cutting volume. The correlation of cutting forces and surface quality with other process parameters shows more complex parameter interaction. The results support industrial acceptance of skiving as a highly productive machining process for hard finish machining and as an alternative to gear grinding and honing.


[ 127 ] Klose, J.; Zanger, F. & Schulze, V. (2019), "Gear skiving of external gears with internally geared tools". VDI Berichte 2355, eds. VDI Wissensforum GmbH, pp. 1579-1590.
Abstract:
Gear skiving is a continuously generating machining process used to manufacture internal and external gears. The tool is a pinion like cutter that is meshing with the workpiece. Cutting conditions in skiving of internal gears are considered more beneficial due to the tool enveloping the workpiece. The skiving process of internal gears is inversed to convey the enveloping tool motion to external gear manufacturing. The internal skiving tool is similar to the tool ring in whirling. Whirling is used for finish machining of threads with high surface requirements and difficult machining parameters, like orthopedic screws from titanium alloys or lead screws from hardened steels. The goal is to take advantage of the beneficial tool engagement of the whirling process for machining of gears. The cutting conditions of gear skiving with an internal tool are simulated equivalent to whirling processes. The impact of different tool diameters and axis crossing angles on cutting thickness and feed marks are studied. The results are examined and compared to an equivalent conventional skiving process. Based on the simulations, experiments with two different internal tool rings with a single straight sided cutting insert are conducted. The results show that the enveloping tool engagement results in smaller cutting thickness, more beneficial chip flow and lower surface roughness allowing higher feeds. The inversed process variant of skiving could thus be an alternative for future machining of external gears.


[ 128 ] Neuenfeldt, P.; Kacaras, A.; Zanger, F. & Schulze, V. (2019), "Optimization of the stream finishing process for mechanical surfacetreatment by numerical and experimental process analysis". Symposium Mechanical Surface Treatment 2019: 8th Workshop Machine Hammer Peening, eds. Wbk Institute of Production Science, K., pp. 138-149.
Abstract:
The stream finishing process represents an efficient mass finishing process capable in mechanical surface modification. In order to generate a deeper understanding of the cause-effect relationships, normal forces, material removal and surface topography were analyzed and correlated for varied process parameters of disc-shaped AISI 4140 specimens. Local resolution of tangential velocities of the particles and normal forces on the workpiece’s surface were simulated using the discrete element method for defined process parameter configurations and were correlated with experimental results. A deep process understanding is accomplished enabling the process design for efficient surface smoothing and improved residual stress depth distribution.


Peer-reviewed articles in books and monographic series

[ 1 ] Schulze, V. & Michna, J. (2011), "Trennen von metallischen Leichtbauwerkstoffen" in Handbuch Leichtbau: Methoden, Werkstoffe, Fertigung, eds. F. Henning, F. H. & E. Möller, E. M., Carl Hanser Verlag GmbH & CO. KG, München, pp. 531-553. ISBN/ISSN: 3-446-42267-6
Abstract:
Nach DIN 8580 bildet das Trennen die dritte Hauptgruppe der Fertigungsverfahren und wird als das Fertigen durch Aufheben des Zusammenhalts von Körpern definiert, wobei der Zusammenhalt teilweise oder im Ganzen vermindert wird. Dabei ist die Endform des späteren Bauteils in der Ausgangsform enthalten. Das Trennen wird außerdem in die Gruppen Zerteilen, Spanen mit geometrisch bestimmten Schneiden, Spanen mit geometrisch unbestimmten Schneiden, Abtragen, Zerlegen und Reinigen unterteilt. Das folgende Kapitel beschränkt sich auf die vier erstgenannten Gruppen des Trennens, weshalb auch nur diese in der obigen Abbildung aufgeführt werden. Innerhalb der Gruppen werden jeweils ausgewählte Fertigungsverfahren kurz vorgestellt und anschließend hinsichtlich der trennenden Bearbeitung von metallischen Leichtbauwerkstoffen betrachtet. Wichtige Aspekte sind dabei die Qualität des Werkzeugs und die auftretende Reibung zwischen Werkzeug und Werkstück. Sie nehmen Einfluss auf den Verschleiß des Werkzeugs und die Qualität der Schnittkante.

Diese Probleme und ihre mögliche Lösung in der industriellen Praxis werden für die verschiedenen Leichtbaulegierungen von Magnesium, Aluminium und Titan beschrieben. Außerdem werden spezifische Aspekte wie der Werkzeugverschleiß behandelt.



[ 2 ] Schulze, V. & Klotz, S. (2014), "Trennen von faserverstärkten Kunststoffen" in Handbuch Spanen, eds. Heisel, U.; Klocke, F.; Uhlmann, E. & Spur, G., Carl Hanser Verlag, München, pp. 1241-1253. ISBN/ISSN: 978-3-446-42826-3
Abstract:
Verbundwerkstoffe aus faserverstärkten Kunststoffen (FVK) werden meist endkonturnah hergestellt. Das bearbeitete Volumen ist daher meist gering im Vergleich zu Metallen. Dennoch ist eine nachfolgende Bearbeitung in Form von Entgraten oder Besäumen der Bauteile sowie die Herstellung von Funktionsflächen in der Regel unumgänglich. Die dabei auftretenden besonderen Herausforderungen bei trennender Bearbeitung lassen sich auf die heterogene Werkstoffzusammensetzung und die stark unterschiedlichen mechanischen sowie thermischen Eigenschaften von Matrix- und Faserwerkstoff zurückführen. Diese Charakteristika, die dem Verbundwerkstoff seine typischen Gebrauchseigenschaften verleihen, verursachen andererseits Probleme bei der Bearbeitung. Eine weitere Schwierigkeit ergibt sich aus der anisotropen Orientierung der Verstärkungsfasern, die auf das spätere Lastkollektiv des Bauteils ausgelegt ist. Belastungen durch Bearbeitungskräfte in Dicken-Richtung führen dazu, dass die Belastung über die Matrix in die Fasern geleitet wird und diese somit quer beansprucht werden, was zum Faser- sowie Grenzflächenversagen in der Nachbarschaft der Lasteinleitungsstelle führt. Das Resultat sind Bauteilschädigungen durch die Bearbeitung in Form von mechanischem oder thermischem Werkstoffversagen. Diese Herausforderungen, die resultierenden Schädigungen und sich daraus ergebende Qualitätskriterien sind bereits in den 1980er und 1990er Jahren ausführlich beschrieben worden (König et al. 1985), stellen aber auch heute noch bei Bearbeitungsaufgaben die relevanten Grundlagen dar.


Non-peer-reviewed articles in journals

[ 1 ] Peichl, A.; Hüntrup, V.; Spath, D.; Schulze, V. & Löhe, D. (2000), "Einfluss des Waermebehandlungszustands auf Mikrozerspanbarkeit von Staehlen", HTM Härterei-Technische Mitteilungen, pp. 195-204.

[ 2 ] Peichl, A.; Hüntrup, V.; Spath, D.; Schulze, V. & Löhe, D. (2000), "Determination of heat treatment states fir for microcutting of steels", MicroMat 2000 - Proceedings, pp. 976-979.
Abstract:
Microcutting of microcomponents made of steel which have to bear high loadings imposes severe Problems concerning the Tools and the materials states of the workpieces. Microcutting allows no subsequent processes which may cause distortions and Need costly reoperations. Therefore microcutting has to be performed in materials states which are heat treated and already possess the high strength necessary during Operation. As These states may be difficult to machine, an Optimum of machinability and service properties is expected at intermediate strengths. The investigations shown in this paper deal with the Determination of this Optimum at the steel SAE 1045 (German grade CK 45), in which grooves were micromachined by milling after different heat Treatments. For each of them, the cutting velocity was varied. The materials states close to the surface produced by these processes were characterized using different techniques. This allows the determination of heat Treatment states and cutting velocities suitable for microcutting.


[ 3 ] Spath, D.; Barrho, T.; Knoll, M.; Löhe, D. & Schulze, V. (2003), "Mikrourformen - der SFB 499. Entwicklung, Produktion und Qualitätssicherung urgeformter Mikrobauteile aus metallischen und keramischen Werkstoffen", wt Werkstattstechnik online, no. 3, pp. 136-140.
Abstract:
The “Institut für Werkzeugmaschinen und Betriebstechnik (wbk)”, “Institut für Maschinenkonstruktionslehre und Kraftfahrzeugbau” (mkl), “Institut für Werkstoffkunde I” (iwk I) and the “Institut für Werkstoffkunde II” (iwk II) of the Universität Karlsruhe (TH) together with the “Institut für Materialforschung 3” (IMF III) of the Research Center Karlsruhe and the “Institut für Mikrosystemtechnik” (IMTEK) of the University Freiburg are working together in the collaborative research center SFB 499 “Development, production and quality control for molded microcomponents made out of metallic and ceramic materials”. This project is sponsored by the Deutsche Forschungsgemeinschaft (DFG, German Research Council)


[ 4 ] Auhorn, M.; Kasanicka, B.; Beck, T.; Schulze, V. & Löhe, D. (2003), "Microstructure, surface topography and mechanical properties of slip cast and powder injection moulded microspecimens made of circonia", Z. Metallkde , pp. 599-605.
Abstract:
Investigations on ceramic microspecimens made of Y2O3-stabilized ZrO2 produced by slip casting or micro powder injection moulding are introduced. During the production of the microspecimens, feedstocks and sintering conditions were varied. Differently moulded specimens were examined with respect to their microstructure and surface topography using light microscopy, scanning electron microscopy (SEM) and confocal white light microscopy. Additionally, the mechanical characteristics were investigated by three-point bending tests using a micro universal testing device. The statistical analysis was realised by means of the Weibull theory and interpreted by the aid of SEM images of fracture surfaces. This research allowed to understand correlations between different feedstocks used, process parameters like the sintering conditions applied and the resulting characteristics as well as material properties of the microspecimens. These results could be used to improve the production process. (orig.)


[ 5 ] Barreiro, P.; Schulze, V. & Löhe, D. (2004), "Einfluss kombinierter Nd:YAG- und Hochleistungsdioden- Laserstrahlschweißprozesse auf die mechanischen Eigenschaften von Al6060 bei quasistatischer Beanspruchung", Aluminium (2004), pp. 1392-1395.
Abstract:
Hochleistungsdiodenlaser sind neue Fügewerkzeuge für die industrielle Fertigung, die zu Nd:YAG-Lasern komplementäre Eigenschaften aufweisen. Es ist daher naheliegend, Hybridschweißprozesse unter Nutzung beider Arten von Strahlquellen zu entwickeln und zu untersuchen, ob sich deren Vorteile vereinigen lassen. Hierzu wurde am Institut für Werkzeugmaschinen und Betriebswissenschaften der Technischen Universität München (iwb) eine Anlage aufgebaut, in der I-Naht-Schweißungen von Blechen aus der Aluminiumlegierung AA6060 vorgenommen wurden. In der vorliegenden Arbeit wird der Einfluss von Prozessparametern auf Geometrie, Mikrostruktur und mechanische Eigenschaften der Schweißnähte untersucht.


[ 6 ] Beck, T.; Schneider, J. & Schulze, V. (2004), "Characterisation and Testing of Microspecimen", Microsystem Technologies, pp. 227-232. 10.1007/s00542-003-0350-7
Abstract:
Currently for the design of micro components often no reliable material data is available. Therefore in the German Collaborative Research Centre (SFB) 499 [1] metallic and ceramic micro specimen that are manufactured by different micro moulding techniques as micro casting, slip casting or micro powder injection moulding are investigated with respect to their microstructure, mechanical and tribological properties. As metal was investigated a AuAgCu-alloy named Stabilor G and as ceramic was investigated ZrO2. Additionally the wear behaviour of mould inserts made of different materials as X38CrMoV5–1, Ni and Cu63Zn37 and the modifications of near surface microstructures due to micro milling in X38CrMoV5–1 in different heat treatment states are presented.


[ 7 ] Delonnoy, L.; Hochrainer, T.; Schulze, V.; Löhe, D. & Gumbsch, P. (2005), "Similarity considerations on the simulation of turning processes of steels", Z. Metallkunde, pp. 761-769.
Abstract:
In order to investigate size effects occurring in the miniaturization of turning processes a complete dimensional analysis using a materials model for high-speed deformation was performed. The derived dimensionless similarity numbers were used to guide the parameter variation in simplified two-dimensional finite-element simulations for orthogonal cutting. The rate-dependent material model leads to size effects like an increase of the specific cutting force while reducing the cutting depth. A counter-intuitive dependence of the cutting force on cutting velocity is explained using a shear-plane model. The derived dependencies on single input parameters are used to predict output values while simultaneously changing several input parameters.


[ 8 ] Weidenmann, K. A.; Fleck, C.; Schulze, V. & Löhe, D. (2005), "Materials Selection Process for Compound-extruded Aluminum Matrix Composites", Advanced Engineering Materials, pp. 1150-1155.

[ 9 ] Trapp, N.; Fiderer, M.; Lütjens, J.; Ehlers, M. & Schulze, V. (2006), "Computer Aided Simulation of Heat Treatment (C.A.S.H.) - Teil 4: Strategien zur Wärmebehandlungssimulation komplexer Stahl-Bauteile", Härtereintechnische Mitteilungen, pp. 25-33.
Abstract:
Die Simulation von Wärmebehandlungsprozessen wie dem Einsatzhärten wurde bis heute meist an einfachen Geometrien durchgeführt. In der industriellen Praxis besteht allerdings die Notwendigkeit, oft große, komplexe Geometrien zu berechnen. Dies ist mit dem heutigen Stand der Technik in einer vernünftigen Zeit nur beschränkt möglich. Strategien zur effizienten Berechnung von Wärmebehandlungsprozessen wurden daher erarbeitet und getestet. Eine dieser Strategien ist die Verwendung eines so genannten Baukastens, in dem wiederum drei Methoden zusammengefasst sind. Eine dieser Methode ist das “Submodelling“, bei dem lokale Geometrieelemente freigeschnitten und mit Randbedingungen aus einer vereinfachten Simulation des Gesamtbauteils beaufschlagt werden. Die zweite hier vorgestellte Strategie ist die “Substitutions-Methode“, bei der Geometrieelemente durch Elementschichten mit bestimmten Eigenschaften ersetzt werden, so dass das Gesamtverhalten identisch bleibt. Die dritte und letzte untersuchte Strategie ist die Methode der “lokalen Netzverfeinerung“, bei der lokale Geometrieelemente ein deutlich feineres Netz als das Gesamtbauteil aufweisen. Ausgewählte Ergebnisse der drei Strategien werden im Folgenden dargestellt und mit experimentell bestimmten Kennwerten hinsichtlich Gefügeverteilung, Spannungen und Maß- und Formänderungen an zwei komplexen Geometrien verglichen.


[ 10 ] Auhorn, M.; Kasanicka, B.; Beck, T.; Schulze, V. & Löhe, D. (2006), "Mechanical strength and microstructure of Stabilor-G® and ZrO2 microspecimens", Microsystems Technologies, pp. 713-716.
Abstract:
For a safe design of micromechanical components reliable data of mechanical properties at static and cyclic loadings are of vital interest. Such data together with a detailed analysis of the microstructure are also useful for a straight forward optimization of the manufacturing process. Therefore, in the present study the mechanical behavior of microcast Stabilor-G microspecimens under quasistatic and cyclic loadings and of slip cast and micro powder injection molded ZrO2 microspecimens under quasistatic loadings was determined. Together with a microscopic characterization of the specimens it could be shown that the elastic-plastic behavior of Stabilor-G microspecimens is strongly determined by grain anisotropy. In fatigue tests cyclic hardening occurs. The scatter of the lifetimes is not larger than observed at cast macrospecimens. The failure behavior of ZrO2 microspecimens under quasistatic bending is mainly determined by surface roughness and near surface porosities as well as by the edge geometry. The highest characteristic bending strength which currently can be reached is nearly 3,200 Mpa.


[ 11 ] Merkel, J.; Schulze, V.; Wanner, A. & Vöhringer, O. (2006), "Stability of residual stresses in longitudinally and transversally deep rolled sintered iron under quasistatic and cyclic loading", Materials Science Forum Vols., pp. 51-56.
Abstract:
In the work presented here the residual stress states of sintered iron (ASC 100.29) were studied after mechanical surface treatments. This included the investigation of the stability of compressive residual stresses of deep rolled sintered iron at different angles relative to the rolling direction at quasistatic and cyclic bending loading. An increase of the compressive residual stress in the transversal deep rolling direction at fatigue loading was found and will be discussed in this presentation.


[ 12 ] Miokovic, T.; Schulze, V.; Vöhringer, O. & Löhe, D. (2007), "Influence of cyclic temperature changes on the microstructure of AISI 4140 after laser surface hardening", Acta Mat. 55 , pp. 589-599. [28.04.16].
Abstract:
In recent years laser surface hardening using pulsed laser sources has become an increasingly established technology in engineering industry and has opened up wider possibilities for the application of selective surface hardening. However, the choice of the process parameters is generally based on experience rather than on their empirical influence on the resulting microstructure, and for hardening processes with cyclic temperature changes, almost no correlations between process parameters and hardening results are known. Therefore, some problems regarding the choice of the process parameters and their influence on the resulting microstructure still remain. In particular, there is a lack of data concerning the effect of cyclic temperature changes on hardening. To facilitate process optimization, this paper deals with a detailed characterization of the microstructures created in quenched and tempered AISI 4140 (German grade 42CrMo4) steel following a temperature-dependent laser surface hardening treatment. The structure properties were obtained from microhardness measurements, scanning electron microscopy investigations and X-ray diffraction analysis of retained austenite.


[ 13 ] Fleischer, J.; Schulze, V.; Kotschenreuther, J.; Löhe, D.; Schneider, J. & Kienzler, A. (2008), "Mechanical structuring, surface treatment and tribological characterization of steel mould inserts for micro powder injection moulding", Microsystem Technologies, pp. 1-7.
Abstract:
Manufacturing of ceramic and metallic micro components in micro powder injection moulding (ìPIM) requires mould inserts offering high wear resistance and a sufficient demoulding behaviour. Within the frame of this research ìPIM mould inserts made from low and high alloyed tool steel were structured by micro milling and finished by micro peening and ultrasonic wet peening. Influence of surface condition on wear and demoulding behaviour of the steels in ìPIM with ceramic feedstock was characterized using a laboratory tribotester simulating powder injection moulding and a specially adapted static friction tester. Results indicate that performance of mould inserts in micro powder injection moulding depends not only on hardness, surface condition and homogeneity of the mould insert materials but also is strongly influenced by the characteristics of the feedstock, like composition of the binder or amount and hardness of the ceramic particles.


[ 14 ] Schulze, V.; Becke, C. & Pabst, R. (2008), "Erhöhte Nachgiebigkeit steigert Standzeiten beim Fräsen", ZWF Zeitschrift für wirtschaftlichen Fabrikbetrieb, pp. 475-479.
Abstract:
Bei der Fräsbearbeitung, besonders von Werkstoffen mit hoher Härte oder solchen mit einer sprödharten Randschicht, treten durch die Verfahrenscharakteristik des unterbrochenen Schnittes hohe mechanische und thermische Wechselbeanspruchungen auf. Vergleichende Untersuchungen zur Dynamik des Antriebstranges von Werkzeugmaschinen mit relativ steifen Motorspindeln und deutlich nachgiebigeren Riemenantrieben haben einen signifikanten Unterschied der erreichbaren Werkzeugstandzeiten belegt, da die Belastungsspitzen beim Schneideneintritt bei Systemen mit höherer Nachgiebigkeit weniger stark ausgeprägt sind [1]. Im Rahmen der hier beschriebenen Arbeiten wurde untersucht, inwieweit durch gezielte Nachgiebigkeitsvariation im Fräswerkzeug Standzeitsteigerungen erreicht werden können. Dazu wurden verschiedene metallische und polymere Werkstoffe in Form von austauschbaren Elementen im Fräswerkzeug integriert und deren Einflüsse auf die Werkzeugstandzeit durch Zerspanversuche ermittelt. Die Ergebnisse versprechen insbesondere für die verwendeten Kunststoffe als Nachgiebigkeitselement signifikante Standzeitvorteile.


[ 15 ] Schulze, V. & Ruhs, C. (2008), "Mit Mikrobahnerosion zum perfekten Formeinsatz", Mikroproduktion, pp. 34-37.

[ 16 ] Schulze, V.; Deuchert, M. & Ruhs, C. (2008), "Kompensation des Größeneffekts Schneidkantenversatz im Mikrofräsprozess", nc transfer 41, pp. 17.
Abstract:
Bei einer Übertragung von Prozessen und Technologien in den Mikrobereich verschiebtsich die Wirkung physikalischer Effekte zueinander. Dieser Vorgang wird Größeneffektgenannt. Im Mikrofräsprozess kann eine solche Verschiebung zum Beispiel anhand der Spindellängung aufgezeigt werden. Ein weiterer Größeneffekt ist die Rundlaufgenauigkeit des Werkzeuges. Diese kann im Mikrobereich bis zu 20 µm betragen, indem sich die Rundlaufungenauigkeiten der Spindel, des Spansystems und des Werkzeuges überlagern und nicht in gleichem Maße mit der Verringerung desWerkzeug Durchmessers mit skaliert werden kann. Diese Veröffentlichung zeigt ein Abrichtverfahren für Mikrowerkzeuge auf, die diesen Fehler kompensiert.


[ 17 ] Schulze, V.; Michna, J.; Pabst, R. & Hauer, T. (2009), "Simulation des Wärmeeintrags verbessert Toleranztreue bei der Trockenbearbeitung", MM Maschinenmarkt, pp. 26-28.
Abstract:
Die Trockenbearbeitung hat sich als Strategie in der Zerspanung etabliert, die deutliche Kostenvorteile im Vergleich zur Nassbearbeitung bietet und zudem verträglicher für Mensch und Umwelt ist. Durch den Wegfall der Schmier- und Kühlfunktion von Kühlschmierstoffen müssen allerdings die Prozessparameter sowie die Gestaltung der Werkzeuge und Maschinen an die veränderten Rahmenbedingungen angepasst werden.


[ 18 ] Schulze, V. & Becke, C. (2009), "Mehrachsige Bohrbearbeitung faserverstärkter KunststoffeGerichtete Prozesskräfte reduzieren die Bauteilschädigung", VDI-Z Integrierte Produktion, vol. 5, pp. 47-49.
Abstract:
Die mechanische Bohrbearbeitung faserverstärkter Kunststoffe birgt aufgrund der heterogenen Werkstoffzusammensetzung und der prozessinherenten Kräfte besondere Herausforderungen. So sind speziell an den Decklagen nach außen wirkende Axialkräfte schädlich für die in Werkstückebene hochfesten Verbundwerkstoffe. Die hier vorgestellten Untersuchungen sollen die schädlichen Kraftkomponenten nicht nur reduzieren, sondern an den empfindlichen Decklagen gezielt ins Werkstückinnere umlenken.


[ 19 ] Schulze, V.; Haupt, S. & Weber, P. (2009), "Hybrid machining of microstructures using a combination of electricaldischarge machining milling and laser ablation.", Journal of Vacuum Science & Technology B 27(2009) 3, vol. 27, no. 3, pp. 1327-1329.
Abstract:
Using laser beam machining with ultrashort laser pulses, microstructures in the micrometer region can be manufactured in virtually all materials, regardless of their mechanical properties. However, machining times are slow if good surface qualities are required. Micro electrical discharge machining (EDM) is also capable of removing material nearly without process forces, but with a higher processing speed if structure sizes exceed a certain value. With the combination of both processes, specific advantages can be realized while disadvantages can be partially eliminated.Therefore, a hybrid machine tool was developed that combines the two processes of ultrashort pulsed laser ablation and EDM milling. No reclamping is necessary. In this study, the limitations and challenges of the single processes are investigated. After that, the novel hybrid machine tool ispresented, along with strategies for the efficient and economic manufacturing of microstructures in materials that are difficult to machine by conventional processes.


[ 20 ] Schulze, V. & Becke, C. (2009), "Taumelfräsen zur schädigungsarmen Bohrbearbeitung von Kompositwerkstoffen", ZWF Zeitschrift für wirtschaftlichen Fabrikbetrieb, vol. 6, pp. 473-477.
Abstract:
Mechanisches Bohren von Kompositwerkstoffen kann aufgrund der Prozesskräfte zu Schädigungen der Bauteile, speziell an den Decklagen, führen. Die in der Regel flächigen Bauteile weisen hohe Festigkeiten in der Werkstückebene auf, sind allerdings aufgrund ihres heterogenen Aufbaus anfällig, wenn Kräfte senkrecht dazu eingeleitet werden. Besonders beim Bohren kann diese Problematik nur schwer umgangen werden. Vorhandene Ansätze reichen von speziell gestalteten Werkzeuggeometrien, der Verwendung von Abstützplatten bis zu mehrachsiger Bearbeitung in Form von Zirkularfräsen. Das gemeinsame Ziel dieser Ansätze ist es, die an den Decklagen nach außen wirkenden Axialkraftkomponenten zu reduzieren. Durch das hier vorgestellte Verfahren Taumelfräsen sollen im Gegensatz dazu die Kräfte nicht nur reduziert, sondern die an den Decklagen resultierenden Axialkräfte gezielt ins Werkstückinnere gerichtet werden. Damit lassen sich Bohrungen mit geringeren Decklagenschädigungen herstellen. In diesem Artikel werden die Prozesskinematik und die sich dadurch ergebenen Prozesskräfte analytisch beschrieben sowie experimentelle Referenzergebnisse vorgestellt.


[ 21 ] Schulze, V.; Ruhs, C.; Kühlewein, C. & Deuchert, M. (2009), "Simulationsgestützte Entwicklung von Mikrofräswerkzeugen", MM Maschinenmarkt, vol. 32, pp. 14-18.
Abstract:
Derzeit erhältliche Mikrofräswerkzeuge wurden von der Geometrie von Makrowerkzeugen abgeleitet. Es hat sich jedoch herausgestellt, dass sich aufgrund von Größeneffekten die Mechanismen der Zerspanung in der Mikrowelt nicht entsprechend derer in der Makrowelt verhalten. Aus diesem Grunde wurde mittels FEM-Simulation schrittweise eine optimierte Mikrofräsergeometrie entwickelt und diese im Anschluss prototypisch hergestellt sowie in Versuchsreihen validiert.


[ 22 ] Schulze, V.; Pabst, R. & Meier, H. (2009), "Simulation von Prozessketten in der Fertigung", JahresmagazIngenieurwissenschaften, vol. 11, pp. 90-93.
Abstract:
Der zentrale Leitgedanke des seit 01.10.2008 von der Deutschen Forschungsgemeinschaft gefärderten Graduiertenkollegs 1483 „Prozessketten in der Fertigung“ ist die Entwicklung von Simulationsmethoden zur Beschreibung, Bewertung und Optimierung von Bauteilzuständen bei verketteten Fertigungsprozessen. Die Projektdurchführung erfolgt durch Partner an der Universität Karlsruhe (TH) und an der Hochschule Karlsruhe sowie am Fraunhofer-IWM in Freiburg. Innerhalb des Graduiertenkollegs werden zwei Prozessketten betrachtet, die von Halbzeugen zu fertigen Bauteilen führen, nämlich ein Massiv- und ein Blechbauteil. Die erzielten Ergebnisse werden durch experimentelle Untersuchungen verifiziert.
Im Teilbereich B wird anhand einer Schaltmuffe die Prozesskette eines Massivbauteils betrachtet, welches in PKW-Getrieben Anwendung findet. Die Prozesskette der Schaltmuffen gliedert sich in Weichbearbeiten - Einsatzhärten - Hartbearbeiten (vgl. Abbildung 1). Hierbei gilt es, die bei der Weichbearbeitung und Wärmebehandlung entstehenden Ei-genspannungen, Verzüge, Verfestigungs- und Randschichtzustände experimentell zu bestimmen und zu analysieren. Mit den gewonnenen Erkenntnissen wird ein Modell erstellt, welches es ermäglicht, den Bauteilzustand zu jeder Zeit innerhalb der Prozesskette zu bestimmen und vorauszusagen. Dies soll dazu genutzt werden, Prozessparameter dahingehend zu optimieren, dass der Hartbearbeitungsaufwand bei gleichzeitiger Optimierung der Bauteileigenspannungen in der Randzone minimiert wird.


[ 23 ] Bauer, W.; Müller, M.; Börsting, P.; Albers, A.; Deuchert, M. & Schulze, V. (2010), "Design and prototyping of a ceramic micro turbine: a case study", Microsystem Technologies, vol. 16, no. 4, pp. 607-615.
Abstract:
Within the framework of the Collaborative Research Center 499 (SFB 499) of the German Research Foundation (DFG), one task was the development of a zirconia micro turbine as a demonstrator tool to enhance the interaction of the participating workgroups. This case study describes the evolution of the demonstrator and experiences gained with the design and the manufacturing of a micro device. Although it was not the aim of this basic research project to develop a commercial product, the experiences are valuable for improving the performance of industrial product development processes for ceramic micro devices. The various parts of the zirconia micro turbine were prepared by a rapid prototyping process chain (RPPC) that allows for a fast and inexpensive manufacturing of ceramic parts with details down to the micron range. A first design concept was made to mainly demonstrate the shaping feasibility of the process in the micro range. However, some features affected the performance due to their low loading capacity. Thus, a modified design was improved for power output and durability. After optimization of the process chain, dense and homogenous ceramic micro parts could be manufactured. These parts were used for the assembling of a functional micro turbine demonstrator, which was powered by compressed air.


[ 24 ] Munzinger, C.; Schulze, V. & Ochs, A. (2010), "Schwingungsunterstütztes Greifen technischer Textilien", VDI-Z Integrierte Produktion, vol. 6, pp. 51-53.
Abstract:
Die Handhabung biegeschlaffer, luftdurchlässiger und forminstabiler Materialien, wie sie im Bereich der endlosfaserverstärkten Kunststoffe vorkommen, stellt in der automatisierten Produktion eine große Herausforderung dar. Für eine wirtschaftliche Großserienfertigung von Faserkunststoffverbundbauteilen (FKV) ist jedoch eine Automatisierung erforderlich. Das schwingungsunterstützte Greifen stellt einen neuen Ansatz auf diesem Gebiet dar. Mit dieser Technik können kurze Taktzeiten bei einem gleichzeitig schonenden Zugriff realisiert werden.


[ 25 ] Schulze, V. & Weber, P. (2010), "Löcher beim Mikrolaserabtragen vermeiden - Einfluss von Werkstückmaterial und Fokuslage auf die Bildung unerwünschter Löcher", wt Werkstattstechnik online, vol. 11, pp. 847-852.
Abstract:
Die voranschreitende Miniaturisierung fordert immer kleinere Bauteile aus verschiedenartigsten Materialien. Mikrolaserabtragen ermöglicht unabhängig von Härte und Festigkeit der Materialien berührungslos und damit nahezu kraftfrei die Herstellung kleinster Kavitäten. Oft treten jedoch beim Laserabtragen unerwünschte Löcher in den bearbeiteten Kavitäten auf, deren Ursache nicht hinreichend geklärt ist. Ziel der Untersuchung ist es, den Einfluss von Fokuslage und Werkstückmaterial auf die Bildung von scheinbar stochastisch auftretenden Löchern bei gleichbleibenden Parametereinstellungen aufzuzeigen.


[ 26 ] Schulze, V. & Ruhs, C. (2011), "Abtragregelung der Mikroerosion maximiert die Genauigkeit", MM Maschinenmarkt, no. 9, pp. 116-119.
Abstract:
In der Mikrofertigungstechnik sind flexible und robuste Lösungen gefragt, um präzise Formeinsätze herzustellen. Mit optischer Sensorik und einer intelligenten, prozessübergreifenden Abtragregelung kann bei der Mikrobahnerosion ein Höchstmaß an Genauigkeit erreicht werden.


[ 27 ] Schulze, V.; Michna, J.; Meier, H.; Pabst, R.; Watts, D.; Lang, H. & Steinert, P. (2012), "Fräsen mit flüssigem Stickstoff als Kühlmedium", wt Werkstattstechnik online, vol. 1, pp. 052-055.
Abstract:
Die spanende Bearbeitung neuer Hochleistungswerkstoffe stellt Maschinen- und Werkzeughersteller vor große Herausforderungen. Der Fachartikel zeigt einen neuartigen Ansatz zur Kühlung von Fräswerkzeugen mit Wendeschneidplatten durch flüssigen Stickstoff (N2liq). Dabei gibt es zwei Besonderheiten: Es soll möglichst nur das Werkzeug gekühlt werden, um negative Effekte im Bauteil zu vermeiden; außerdem gilt es, das tiefkalte Medium von einem stehenden auf ein rotierendes System zu übertragen. Mit dem hierfür entwickelten System wurden umfangreiche Fräsexperimente auf einem Bearbeitungszentrum durchgeführt, welche deutliche Vorteile der kryogenen Kühlung zeigen.

The machining of new high performance materials challenges manufacturers of tools and machine tools. This article presents a new approach of cooling cutting inserts of milling tools using liquid nitrogen (N2liq). The approach considers two specific characteristics: One feature is to cool only the tool itself to avoid negative influences concerning the work piece. A second challenge is the transport of the cryogenic medium from a stationary to a rotating system. By use of the new approach large scale milling experiments have been conducted which show explicit advantages of the cryogenic cooling.



[ 28 ] Schulze, V.; Osterried, J.; Strauß, T. & Zanger, F. (2012), "Analysis of surface layer characteristics for sequential cutting operations", HTM Journal of heat treatment and materials, vol. 67, pp. 347-356. doi: 10.3139/105.110170
Abstract:
For manufacturing processes like milling, broaching and skiving tools with multiple cutting edges are used. The geometry and the characteristics of the machined components are the result of sequential cuts. A finite element model is built up including the sequential cutting by transferring component states between work piece models. The model is validated by comparing residual stresses between numerical and experimental results. Small element sizes allow for a detailed resolution of quantities describing the component state. Characteristics of the specific depth profiles are used for the analysis of residual stresses. The influence of process parameters and the number of simulated sequential cuts are examined. Sequential cuts show an influence on surface residual stresses. Residual stresses decrease for low cutting velocities and slightly increase for high cutting velocities. Tensile stresses also reach to deeper areas of the surface layer with increasing number of cuts. Compressive stresses pass through a significant maximum before decreasing to a constant value. A steady stress state is identified after ten sequential cuts.


[ 29 ] Gerstenmeyer, M.; Klotz, S.; Zanger, F. & Schulze, V. (2013), "Untersuchungen zum Einspannen von FVK", MM Maschinenmarkt Composites World, pp. 14-17.
Abstract:
Faserverstärkte Kunststoffe liegen im trend und müssen nach ihrer meist endkonturnahen Fertigung noch spanend bearbeitet werden, um einsatzfähig zu sein. Was beim Einspannen von Composites zu beachten ist, damit sie nicht beschädigt werden, zeigt folgender Artikel.


[ 30 ] Schulze, V.; Zanger, F.; Boev, N.; Michna, J.; Maas, U. & Faltin, C. (2014), "FE-Simulation of Machining Induced Phase Transformations Considering Friction as a Function of Temperature and Sliding Speed and Detailed Modeling of the Heat Transport", Advanced Engineering Materials, vol. 16, no. 2, pp. 137-141. DOI: 10.1002/adem.201300103
Abstract:
2D-FE-cutting simulation for the steel 42CrMo4 (AISI4140) including the prediction of machining induced phase transformations at the workpiece surface layer. The model predicts thickness, composition and hardness of transformed workpiece material.


[ 31 ] Hoppen, P.; Zanger, F. & Schulze, V. (2014), "Aktive Kompensation des Schneidkantenversatzes", Mikroproduktion, pp. 58-62.
Abstract:
In der Mikrozerspanung haben kleinste Rundlauffehler große Auswirkkungen auf die Standzeiten des Werkzeugs und das Bearbeitungsergebnis. Neue Perspektiven für die hochpräzise Mikrobearbeitung bietet jetzt das WERKZEUGSPANNSYSTEM >µChuck<, das den Versatz der Schneidkante µm-genau kompensiert.


[ 32 ] Fleischer, J.; Schulze, V.; Zanger, F.; Leberle, U.; Boev, N. & Spohrer, A. (2014), "Spanntechnikvergleich bei der Hochleistungszerspanung", VDI-Z, vol. 2, pp. 42-44. [02.04.16].
Abstract:
In einer Studie wurden am wbk - Institut für Produktionstechnik Werkzeughaltersysteme in Hydro-Dehnspanntechnik und Warmschrumpftechnik vergleichend gegenübergestellt. Der Fokus lag auf den bei der Hochleistungszerspanung bedeutsamen Kriterien Produktivität und Werkzeugstandzeit.


[ 33 ] Fleischer, J.; Schulze, V.; Burtscher, J. & Dosch, S. (2015), "Geschwindigkeitsmessung bei gerundeten Strangpressprofilen", VDI-Z Integrierte Produktion, no. 1, pp. 60-62.
Abstract:
Zur Herstellung gekrümmter Profile kommt in einem neuartigen Prozess eine modifizierte Strangpresse zum Einsatz. Die Handhabung der gekrümmten Profile wird mittels zwei auf Industrierobotern fixierten Werkzeugen realisiert. Zur Synchronisation der Handhabungswerkzeuge relativ zum austretenden Strang muss die Geschwindigkeit des Strangs exakt bekannt sein. Vorgestellt wird eine innovative Einrichtung zur Messung der Geschwindigkeit eines bewegten Strangs mithilfe eines „Laser Surface Velocimeters“. Der Laserstrahl wird aufgrund des begrenzten Raums am Pressenaustritt über ein System aus zwei Spiegeln zum Messpunkt umgelenkt. Die Einflüsse der Umlenkung und das Ermitteln der absoluten Messgenauigkeit des Systems werden an einem Versuchsstand untersucht.


[ 34 ] Strauß, T.; Meier, H.; Wanner, A.; Schulze, V. & Gibmeier, J. (2012), "Local residual stress distribution at the tooth root surface of a broached steel component", Materials Science Forum Vols. 706-709, pp. 1731-1736.
Abstract:
Broaching is an important technique for creating tooth structures in mechanical components. In the present work, the effects of the broaching process on the material state in the near surface region at the root of the tooth was analyzed. The studies were carried out on broached plates made from case hardening steel SAE 5120. The cutting speed and machining condition (cooling lubricant, dry machining) were varied. During broaching with a TiAlN coated tool the cutting forces were monitored. Subsequently, the local residual stresses at the root of the tooth were determined using X-ray diffraction. Further, surface roughness and micro hardness measurements as well as microstructure analysis complement the results. The results indicate that cutting forces have a high influence on the development of the residual stress state at the machined surface whereas no significant effect on changes in surface hardness and microstructure could be observed. Dry cutting with relatively high cutting speeds ( 30m/min) result in low cutting forces and hence in high tensile residual stresses in broaching direction.


[ 35 ] Schulze, V.; Uhlmann, E.; Mahnken, R.; Menzel, A.; Biermann, D. & Zabel, A. (2015), "Evaluation of different approaches for modeling phase transformations in machining simulation", Production Engineering. Research and Developmen, pp. 1-21.
Abstract:
Presently, the main mechanism for phase transformations in machining of steels is not absolutely clear and is still subject to research. This paper presents, three different approaches for modeling phase transformations during heating in machining operations. However, the main focus lies on two methods which can be classified into a stress related method and a thermal activation related method for the description of austenitization temperature. Both approaches separately showed very good agreements in the simulations compared to the experimental validation but were never compared in a simulation. The third method is a precalculated phase landscape assigning the transformation results based on a micro-mechanically motivated constitutive model to the workpiece in dependence on the temperature and strain history. The paper describes all three models in detail, and the results are also presented and discussed.


[ 36 ] Weingärtner, R.; Hoffmeister, J. & Schulze, V. (2015), "Mechanische Oberflächenbearbeitung durch Mikrostrahlen", HTM - Journal of Heat Treatment and Materials, vol. 70, no. 2, pp. 59-65. http://dx.doi.org/10.3139/105.110252 [30.11.-1].
Abstract:
Vielfältige Verfahren der mechanischen Oberflächenbehandlung erlauben Änderungen der Randschichteigenschaften, die zur Steigerung der Wechselfestigkeit genutzt werden können. Diese Verfahren beruhen auf einer plastischen Verformung der Oberfläche und führen optimalerweise zu Druckeigenspannungen nahe der Oberfläche und einer Verfestigung durch Änderungen des mikrostrukturellen Zustandes, wie der Korngröße oder der Versetzungsdichte. Damit ist auch stets eine Änderung der Topographie verbunden. Häufig wird das Kugelstrahlen verwendet, welches auch die Bearbeitung komplexerer Geometrien erlaubt. Eine Weiterentwicklung davon stellt das Mikrostrahlen dar, bei dem Strahlmittel mit Durchmessern unter 100 μm eingesetzt wird. Neue Anwendungsmöglichkeiten bietet das Verfahren bei der Bearbeitung dünnwandiger Bauteile, die durch die geringeren Strahlintensitäten ermöglicht wird, oder auch bei schwer zugänglichen Bauteilbereichen infolge kleinerer Geometrien des Strahlsystems. Die Charakterisierung der Randschichteigenschaften erfolgt durch Röntgendiffraktometrie, Konfokal- und Rasterelektronenmikroskopie und Aufnahmen an Querschnitten, die mittels fokussierten Ionenstrahls hergestellt wurden. Die Untersuchungen zeigen, dass sich die resultierenden Oberflächeneigenschaften durch Druckeigenspannungen, eine Verfestigung durch Erzeugung nanokristalliner Randschichten sowie eine gegenüber dem Kugelstrahlen vergleichsweise gute Topographie auszeichnen. Die Eindringtiefe des Verfahrens ist hierbei deutlich stärker auf oberflächennahe Bereiche begrenzt als etwa beim Kugelstrahlen. Wechselbiegeversuche zeigen, dass damit eine deutliche Steigerung der Wechselfestigkeit erzielt werden kann. Die Steigerungen der Wechselfestigkeit beim Kugelstrahlen werden dabei für die untersuchten Probengeometrien nach Mikrostrahlen deutlich übertroffen, sodass sich das hohe Potenzial des Verfahrens zur mechanischen Oberflächenbehandlung zeigt.


[ 37 ] Habschied, M.; Graaff, B. D.; Klumpp, A. & Schulze, V. (2015), "Fertigung und Eigenspannungen", HTM - Journal of Heat Treatment and Materials, vol. 70, no. 3, pp. 111-121. http://dx.doi.org/10.3139/105.110261 [30.11.-1].
Abstract:
Nahezu alle Fertigungsverfahren führen durch inhomogene plastische Verformungen oder lokal unterschiedliche thermische Ausdehnungskoeffizienten zur Ausbildung vonEigenspannungen. Wenn diese aufgrund ihres Vorzeichens die Bauteileigenschaften ungünstig beeinflussen würden, müssen sie nachträglich abgebaut werden. Durch Einstellung geeigneter Prozessführungen können allerdings auch günstige Beeinflussungen der Bauteileigenschaften erreicht werden, sodass diese Prozessvarianten gezielt zur Optimierung von Bauteilzuständen,dem sogenannten Surface Engineering, eingesetzt werden können. Die Zusammenhänge zwischen dem Eigenspannungszustandsind Gegenstand der Arbeit. Dabei wird auf alle Hauptgruppen der Fertigungstechnik eingegangen.


[ 38 ] Merzkirch, M.; Reeb, A.; Weidenmann, K. A.; Wanner, A. & Schulze, V. (2011), "Acoustic Emission Response Of Reinforced Lightweight Metal Matrix Composites During Tensile And Cyclic Loading", Journal of Acoustic Emission, vol. 29, no. 990, pp. 317-328. [30.11.-1].
Abstract:
In the field of lightweight construction for transportation means, hybrid structures composed of high-strength and low-density materials exhibit a high application potential. As a viable approach to increase the stiffness, strength and fatigue life of light-metal sections, spring steel (301SS) wires are incorporated into the matrix material via composite extrusion. This work investigated the deformation and damage behavior of wire-reinforced hybrid samples with aluminum (EN AW-6082) and magnesium (AZ31) matrices under quasi-static and cyclic loads. The mechanical tests are accompanied by acoustic emission (AE) analysis. The results show that the AE analysis allows for the detection of the plastic deformation under pure tensile as well as under cyclic load for both composites. Furthermore, the damage can be detected and located so that the AE analyses lead to a detailed insight to damage mechanisms like crack growth, debonding of the matrix material from the interface and fracture of the components.


[ 39 ] Reeb, A.; Merzkirch, M.; Schulze, V. & Weidenmann, K. A. (2016), "Heat treatment during composite extruded spring steel wire reinforced EN AW-6082", Journal of Materials Processing Technology, vol. 229, no. 990, pp. 1-8. http://dx.doi.org/10.1016/j.jmatprotec.2015.08.022 [30.11.-1].
Abstract:
To increase the specific yield strength and the ultimate tensile strength of a unidirectionally spring steel wire – reinforced composite extruded aluminium alloy (AlMgSi1) matrix composite, investigations of heat treatment states T4 and T6 have been carried out. With respect to the quench sensitivity of the matrix material used and to reduce processing time to avoid unintended interfacial reactions, a setup for direct water quenching at the extrusion press was used and compared to air quenched extrusion profiles. The mechanical investigations showed increased ultimate tensile strength and offset yield strength for water quenched unreinforced and reinforced specimen. The deformation behaviour showed a distinct plateau region where matrix and wire deform plastically which can be explained by multiple necking of the reinforcing element. The characteristic of this region is strongly influenced by the heat treatment state. In order to characterize the interfacial properties, push-out tests were performed. Optical micrographs showed that debonding between matrix and reinforcing element mainly takes place within the matrix material. Therefore the measured debonding shear strength is strongly influenced by the heat treatment state.


[ 40 ] Weddeling, C.; Walter, V.; Haupt, P.; Tekkaya, E.; Schulze, V. & Weidenmann, K. A. (2015), "Joining zone design for electromagnetically crimped connections", Journal of Materials Processing Technology, vol. 225, no. 999, pp. 240-261. http://dx.doi.org/10.1016/j.jmatprotec.2015.06.009 [30.11.-1].
Abstract:
Space frames and multi-material structures are innovative designs to reduce the weight of a vehicle. But both lightweight design concepts have complex demands on joining technologies with the result that conventional processes are often pushed to their technological limits. Joining by electromagnetic crimping provides an interesting alternative to connect such structures without penetration or external heating. During electromagnetic crimping, pulsed magnetic fields are used to form a profile made out of an electrically conductive material into form-fit elements, like grooves, of the other joining partner. Thereby, an interlock is generated, which enables a load transfer. However, existing joint design methodologies require either extensive experimental studies or numerical modeling. To facilitate the connection design, an analytical approach for the prediction of the joining zone parameters with respect to the loads to be transferred is presented in this article. For the validation of the developed approach, experimental studies regarding the load transfer under quasi-static tension are performed. The major parameters considered in these investigations are the groove dimensions and its shape. In order to reduce the mass of a structure, hollow mandrels can be applied. To analyze how the reduced compressive strength of such inner connection elements influences the joining behavior and the load transfer of electromagnetically crimped connections, experimental studies are performed subsequent to the studies on the general groove parameters. Based on the obtained results, design strategies and a process window for the manufacturing of such joints are developed. To show the potential of electromagnetic form-fit joining, example connections joined in accordance with the established design guidelines are tested under quasi-static and cyclic loading.


[ 41 ] Morasch, A.; Reeb, A.; Baier, H.; Weidenmann, K. A. & Schulze, V. (2015), "Characterization of debonding strength in steel-wire-reinforced aluminum and its influence on material fracture", Engineering Fracture Mechanics, vol. 141, pp. 242-259. http://dx.doi.org/10.1016/j.engfracmech.2015.05.029 [30.11.-1].
Abstract:
Extruded steel-wire-reinforced aluminum offers increased ultimate tensile strength in wire direction at low wire contents. Debonding of the wires, however, provokes material failure and, therefore, is the topic of the presented research. Interface normal strength and axial shear strength are assessed experimentally and the material’s sensitivity toward its interface normal strength is analyzed. Using a shear-modified Gurson fracture model, the effect of wire debonding on the fracture behavior of the material is studied. Therefore, bolt-pull-out tests are performed, allowing for a validation of the material and fracture modeling. A further comparison of the fracture behavior is drawn to non-reinforced aluminum


[ 42 ] Reeb, A.; Walter, V.; Schulze, V. & Weidenmann, K. A. (2015), "Characterization of a hybrid Al2O3–aluminum matrix composite manufactured via composite extrusion [in press]", Journal of Composite Materials, vol. 50, no. 8, pp. 1099-1108. http://dx.doi.org/10.1177/0021998315587317 [30.11.-1].
Abstract:
The development of new metal matrix composites for lightweight applications is aiming for an increase in specific strength and stiffness compared to conventional light metal alloys. The composite extrusion process is a promising manufacturing method for continuously reinforced light metal profiles. Especially the reinforcement with ceramic fibers leads to an increase in the specific strength and stiffness. For these investigations a hybrid composite is produced by using an Al2O3-fiber/AlMg0.6 composite wire which is embedded in an EN AW-6082 aluminum matrix. It is shown that the mechanical properties of the composite exceed those of the unreinforced matrix material. An explicit investigation of the deformation and damage behavior of this composite is given by optical strain analysis and in situ tensile tests in an X-ray micro computed tomograph (µ-CT). It was observed that during tensile loading multiple fracture of the composite wire occurs while exceeding the strain limit of the non-embedded composite wire. It could be shown that fracture of the composite wire is accompanied by strain localization and therefore strain hardening occurs in vicinity of the internal fracture, which leads to multiple necking of the specimen. The µ-CT analysis reveals the intrinsic damage mechanisms and shows the beginning of ceramic fiber fracture which showed evidence for a local load distribution between the fibers resulting in a planar fracture of the composite wire. The multiple fracture of the wire allows for an interface shear strength analysis and indicates a good bonding of the composite wire.


[ 43 ] Merzkirch, M.; Hammers, T.; Reeb, A.; Schwind, T.; Riedl, S.; Thiel, L.; Henschel, A.; Kerscher, E.; Schulze, V. & Weidenmann, K. A. (2015), "Fatigue Behavior and Lifetime Prediction of Unidirectionally Wire Reinforced Lightweight Metal Matrix Composites [Preprint]", Advanced Engineering Materials, vol. 99, no. 99, pp. 905-911. http:/dx.doi.org/10.1002/adem.201400354 [30.11.-1].
Abstract:
In the field of lightweight construction for transportation means, hybrid structures composed of highstrength and low-density materials exhibit a high potential for application. The composite extrusion process allows an easy embedding of metallic reinforcements into a multitude of light metal alloys. The current work shows that different metallic wire reinforced light alloys with a content of 11.1 vol% lead to a significant increase in lifetime of different aluminum and magnesium alloys under fully reversed stress controlled fatigue loading. Based on the knowledge of the quasi-static behavior of the single components and the fatigue behavior of the matrix material, a new lifetime model is used to predict the lifetime for different unidirectionally reinforced material systems.


[ 44 ] Merzkirch, M.; Meissner, M.; Schulze, V. & Weidenmann, K. A. (2015), "Numerical analysis to study the tensile behaviour of a spring-steel-wire-reinforced aluminium alloy metal matrix composite [Preprint]", Journal of Composite Materials, vol. 49, no. 21, pp. 2659-2671. http://dx.doi.org/10.1177/0021998314553044 [30.11.-1].
Abstract:
The reinforcement of composite extruded light metal profiles offers a high potential in terms of weight reduction and the improvement of mechanical properties, both of which are essential for components in lightweight space frame constructions. In a previous study, the mechanical properties under tensile loading of spring-steel (301SS)-wire-reinforced aluminium extrusions based on EN AW-6082 were investigated in terms of a varying reinforcing ratio. The aim of the current study is to minimize the effort needed to gather mechanical data by calculation of the deformation and damage behaviour under tensile loading of 11.1 vol.% spring-steel-reinforced EN AW-6082. The simulation of the push-out test provided specific parameters concerning the interfacial properties – like the radial strength – needed for modelling the tensile test. It could be shown that the simulation of the tensile test is in good agreement with the experimental results, concerning quantitative values (stress–strain curve) and qualitative behaviour (necking and debonding).


[ 45 ] Reeb, A.; Schweizer, L.; Weidenmann, K. A. & Schulze, V. (2014), "Characterization of unreinforced and steel wire reinforced magnesium alloy AZ31 under mechanical-corrosive loading", Procedia CIRP, vol. 18, no. 99, pp. 114-119. http://dx.doi.org/10.1016/j.procir.2014.06.117 [30.11.-1].
Abstract:
In this work the sensitivity of an unreinforced and steel wire reinforced AZ31magnesium alloy to stress corrosion cracking is investigated by means of static stress corrosion testing (clamping Lever tests) and cyclic stress corrosion testing (crack Propagation tests). In static mechanical-corrosive testing, the AZ31 alloy showed a relatively low sensitivity while the composite showed a higher sensitivity with earlier crack Initiation due to weakening of the loaded specimen section. In cyclic experiments, hydrogen embrittlement crack growth acceleration could be attested. Reinforcing the Matrix material leads to a compensation of the crack growth acceleration due to stress corrosion cracking by crack energy Absorption by increased Interface damage according to the aggressiveness of the corrosive media.


[ 46 ] Kümmel, J.; Gibmeier, J.; Schulze, V. & Wanner, A. (2014), "Effect of built-up edge formation on residual stresses induced by dry cutting of normalized steel", Advanced Materials Research, vol. 996, no. 99, pp. 603-608. http://dx.doi.org/10.4028/www.scientific.net/AMR.996.603 [30.11.-1].
Abstract:
The tool and workpiece surface layer states of the tribosystem uncoated WC-Co cutting tools vs. normalised SAE 1045 workpiece material are studied in detail for a dry metal cutting process. Within the system the cutting parameters (cutting speed, feed rate, cutting depth) determine the wear state of the cutting tool and the resulting surface layer state (residual stress) in the workpiece. As the built-up edge can be used as a possible wear protecting layer [1] the influence of built-up edge and wear behaviour of the cutting tool was examined with respect to the workpiece surface layer state for knowledge based metal cutting processing. Small compressive stresses (-60-80 MPa) are induced in the surface layer, that are nearly homogeneous for the highest built-up edge, which lead to the lowest tool wear in combination with lowest cutting temperature.


[ 47 ] Merzkirch, M.; Meissner, M.; Schulze, V. & Weidenmann, K. A. (2014), "Tensile behaviour of spring steel wire reinforced EN AW-6082", Journal of Composite Materials, vol. 49, no. 3, pp. 262-274. http://dx.doi/org/10.1177/0021998313517581 [30.11.-1].
Abstract:
The reinforcement of composite aluminium extrusions offers a high potential regarding weight reduction and improvement of mechanical properties, which is essential for components in lightweight constructions. The current work gives an overview of the quasi-static properties of spring steel wire reinforced EN AW-6082 with varying reinforcing ratio. The deformation and damage behaviour is investigated in detail for a reinforcing ratio of 11.1 vol.%. It is shown that the relatively ductile behaviour of the spring steel wire leads to multiple necking resulting in higher strains than expected. Current models are expanded and modified for a proper adaptation to the material system


[ 48 ] Schwenk, M.; Hoffmeister, J. & Schulze, V. (2014), "Experimentally validated residual stresses and distortion prediction for dual frequency induction hardening", International Journal of Applied Electromagnetics and Mechanics, vol. 44, no. 2, pp. 127-135. http:/dx.doi.org/10.3233/JAE-141752 [30.11.-1].
Abstract:
Dual frequency induction hardening can be a low distortion alternative to case hardening for gearings. However, profound process understanding is still lacking, which is reflected by the absence of appropriate models allowing the prediction of final component properties in terms of residual stresses and distortion. In order to close this gap, a 2-D numerical model has been developed, considering short time austenitization kinetics of quenched and tempered AISI 4140. The induction heating model considering the nonlinear magnetic material behaviour is realized with MSC.Marc®, whereas the mechanical response is implemented in Abaqus/Standard®. The comparison of residual stresses and distortion with experimental results shows that the developed model is in good agreement. Numerical investigations have shown that the core temperature and the TRIP strain during the martensitic transformation will determine the quantitative distribution of the residual stresses


[ 49 ] Merzkirch, M.; Reeb, A.; Schulze, V. & Weidenmann, K. A. (2014), "Cyclic deformation and damage behaviour of the spring steel wire reinforced aluminium alloy EN AW-6082", Journal of Materials Science, vol. 49, no. 5, pp. 2187-2203. http://dx.doi.org/10.1007/s10853-013-7913-5 [30.11.-1].
Abstract:
The demand for lightweight materials used for constructions in automotive applications, e.g. space frames, requests for composite materials such as reinforced aluminium extrusions with a high specific stiffness and strength. This contribution shows that a spring steel wire reinforcement content of 11.1 vol% leads to a significant increase in fatigue life of monofilament composite extrusions based on the aluminium alloy, EN AW-6082, in heat treatment state T4 under stress controlled fatigue loading. As groundwork, the cyclic deformation and damage behaviour of the unreinforced matrix material is investigated in detail. Beside the determination of three stages of deformation and damage, the reason for the high fatigue strength in comparison to the quasi-static offset yield strength is also clarified. The main aim of the research focusses on the description of the mechanisms and mechanics of constituent deformation and damage evolution of 11.1 vol% spring steel wire reinforced EN AW- 6082, which is presented quantitatively and qualitatively by metallographic means. The three stages represent the deformation and damage of the matrix material, whereas the fourth stage is characterised by the fatigue of the reinforcing element. Based on the knowledge of the quasistatic behaviour of the single components and the fatigue behaviour of the single matrix material, a new lifetime model is deduced from the strain response in order to predict the fatiguelife for unidirectionally reinforced material systems.


[ 50 ] Kümmel, J.; Gibmeier, J.; Müller, E.; Schneider, R.; Schulze, V. & Wanner, A. (2014), "Detailed analysis of microstructure of intentionally formed built-up edges for improving wear behaviour in dry metal cutting process of steel", Wear, vol. 311, no. 1, pp. 21-30. http://dx.doi.org/10.1016/j.wear.2013.12.012 [30.11.-1].
Abstract:
Tool wear is a very important factor determining tool life and surface quality of a machined workpiece surface. In the range of small cutting geometries the cutting depth can be in the range of the cutting edge radius, hence, it promotes the development of built-up edges (BUE). A systematic and comprehensive examination of built-up edge formation and associated microstructural features is still lacking. In the present study a targeted examination of microstructural features of the built-up edge was carried out with uncoated WC/Co as cutting tool and SAE 1045 steel as workpiece material. The process parameters were chosen so that the built-up edge formation was provoked. The dimensions of the built-up edge were assessed by light-optical microscopy (LOM) and scanning electron microscopy (SEM). The microstructure of the adhering built-up edge was revealed using new nonconventional metallographic methods. The nanocrystalline grain structure of the built-up edges was analysed by means of focused ion beam (FIB) inspection and preparation as well as transmission electron microscopy (TEM) in combination with energy-filtered TEM (EFTEM). The investigated built-up edges showed a highly deformed microstructure and a possible protecting effect could be concluded with respect to the cutting tool for certain cutting speed regimes. The built-up edge can be considered as a protecting surface layer formed in-situ during the metal cutting process with different microstructural states of ferrite and cementite. The developed microstructures show similar properties as microstructures produced by severe plastic deformation processes. In addition to built-up edge and wear examinations, the resulting surface layer states in the machined workpiece were determined using a stylus instrument for surface roughness measurement and by means of X-ray diffraction for residual stress analysis.


[ 51 ] Nusskern, P.; Hoffmeister, J. & Schulze, V. (2014), "Simulation of the manufacturing process of case-hardened powder metallurgical components: carburizing simulation", Advanced Engineering Materials, vol. 16, no. 2, pp. 147-150. http://dx.doi.org/10.1002/adem.201300101 [30.11.-1].
Abstract:
In many cases, powder metallurgical components are heat treated in order to improve the component behavior. An established heat treatment technique for wrought materials is case-hardening. But up to now, this procedure is not applied for powder metallurgical components, since the existing porous microstructure avoids adjusting a defined carbon depth profile. As a consequence a carbonization of the core and a full hardening can occur, leading to a disadvantageous phase and residual stress distribution. However, a new approach for case hardening of powder metallurgical components is to perform a surface densification prior to the heat treatment. In this study this approach is realized by using a deep rolling process. In order to verify the functionality of the process chain, the surface integrity was analyzed after each processing step using X-ray diffraction measurements and materialographic methods. There is clear evidence that the open porous structure could be transferred into a surface densified graded porous layer. As a consequence the carburization is dominated by solid state diffusion enabling to adjust a defined carbon depth profile leading to a martensitic surface layer and compressive residual stresses in the near surface zone. Subsequent fatigue strength experiments for sintered samples as well as for additional densified or densified plus case-hardened specimens were performed in order to demonstrate the enhanced mechanical properties. A significant increase in fatigue strength can be measured.


[ 52 ] Merzkirch, M.; Schulze, V. & Weidenmann, K. A. (2013), "Lifetime behaviour of unidirectionally wire reinforced lightweight metal matrix composites", International Journal of Fatigue, vol. 56, no. 99, pp. 60-68. http://dx.doi.org/10.1016/j.ijfatigue.2013.08.002 [30.11.-1].
Abstract:
In the field of lightweight construction for transportation means, hybrid structures composed of high-strength and low-density materials exhibit a high application potential. The current work shows that a spring steel wire reinforcement content of 11.1 vol.% leads to a significant increase in lifetime of the magnesium alloy AZ31 under stress controlled fatigue loading. Based on the knowledge of the quasi-static behaviour of the single components and the fatigue behaviour of the single matrix material and on the understanding of mechanisms and mechanics of constituent deformation and damage evolution a new model is deduced from the quantitative strain response in order to predict the lifetime for different unidirectionally reinforced material systems.


[ 53 ] Schwenk, M.; Hoffmeister, J. & Schulze, V. (2013), "Experimental Determination of Process Parameters and Material Data for Numerical Modeling of Induction Hardening", Journal of Materials Engineering and Performance, vol. 22, no. 7, pp. 1861-1870. http://dx.doi.org.10.1007/s11665-013-0566-3 [30.11.-1].
Abstract:
Induction surface hardening is a widely used manufacturing process to improve the mechanical properties of components. However, better process understanding as well as process development requires numerical modeling. The modeling itself depends on the input data in terms of process parameters and the material behavior. Data acquisition is a rather difficult task due to very short processing times, as seen in contour hardening of gears. The article will give an overview over critical aspects regarding the acquisition of input data. A short presentation of the numerical model used to compare experimental and numerical results shall promote better understanding for improving the modeling or reducing the model complexity necessary for good predictability.


[ 54 ] Schwenk, M.; Kaufmann, B.; Hoffmeister, J. & Schulze, V. (2013), "Modelling of Strain Rate and Temperature Dependent Flow Stresses of Supercooled Austenite for AISI 4140", Materials Science Forum, vol. 762, no. 999, pp. 122-127. http://dx.doi.org.10.4028/www.scientific.net/MSF.762.122 [30.11.-1].
Abstract:
The numerical modelling of heat treatment has become an essential tool in understanding distortion potentials for case hardening. When looking at other surface hardening processes such as induction or laser hardening, high heating and cooling rates automatically lead to higher strain rates during the heat treatment cycle. So far, there have been almost no investigations on the strain rate as well as temperature dependency of the mechanical properties of supercooled austenite. In this paper, the typical induction and laser hardening steel AISI 4140 has been used in order to determine the influence of strain rate and temperature on the mechanical behaviour. The experiments are based on tensile tests, using a specifically designed thermo-mechanical simulator. The experimental results show that a positive strain rate sensitivity for strain rates up to 1 s-1 results. Especially in the temperature interval where austenite formation occurs during heating, the strain rate sensitive flow stress might lead to an alteration of the plastic strains in comparison to conventional heat treatments at low heating rates. The material model presented in this paper allows a good reproduction of the experimental data over a wide range of strain rates and temperatures.


[ 55 ] Habschied, M.; Dietrich, S.; Heussen, D. & Schulze, V. (2016), "Performance and Properties of an Additive Manufactured Coil for Inductive Heat Treatment in the MHz Range", HTM - journal of heat treatment and materials, vol. 71, no. 5, pp. 212-217. http://dx.doi.org/10.3139/105.110294 [30.11.-1].
Abstract:
In inductive heat treatment, the induction coil design plays an important role in the localization of heat generation. Therefore, the combination of an optimized coil geometry and frequency choice determines the workpiece properties and applicability of close-to-contour hardening for small parts or thin hardened layers. Additive manufacturing of copper alloys in the Selective Laser Melting (SLM) process offers a method to build coils with high design flexibility and precision. Conventional coil manufacturing methods are reaching their limitations due to the conflicting geometry specifications at the applied frequency range. In the present work, a characterization is presented and the performance of an SLM manufactured coil in MHz induction application of small surface hardened wires of steel is examined.


[ 56 ] Schulze, V.; Bleicher, F.; Groche, P.; Guo, Y. & Pyun, Y. (2016), "Surface modification by machine hammer peening and burnishing", CIRP annals, manufacturing technology, vol. 65, no. 2, pp. 809-832. http://dx.doi.org/10.1016/j.cirp.2016.05.005 [30.11.-1].
Abstract:
Abstract A wide range of surface modification processes has been developed over the past decades. Beside the well-established processes such as shot peening, there are other emerging surface modification processes such as machine hammer peening with a potential of applications that still needs to be evaluated. Therefore, all surface modification processes using guided tools with periodic or continuous contact to the workpiece are compared in this paper. After a classification of the processes, the paper presents a systematic description by comparing the different technologies and it explains the proposed standardized nomenclature. It identifies the relevant physical mechanisms of the surface modifications processes and it compares the influences on surface roughness, residual stresses, work hardening and microstructure. One section is dedicated to the need of an accompanying quality assurance. Furthermore, the capabilities of different process simulation approaches are analyzed with respect to process mechanisms and the resulting surface layer characteristics. The service performance such as fatigue life, corrosion resistance, friction and wear are discussed based on best practice results. Finally, the paper discusses the actual and potential applications of surface modification processes: surface strengthening, post welding treatments, smoothing of tools and molds as well as surface structuring and embedding of coating materials.


[ 57 ] Schulze, V.; Lang, K.; Voehringer, O. & Macherauch, E. (1998), "Zum Wechselverformungsverhalten von vergütetem 42 CrMo 4 bei zweistufiger Zug-Druck-Beanspruchung", [30.11.-1].

[ 58 ] Menig, R.; Schulze, V. & Voehringer, O. (2002), "Effects of static strain aging on residual stress stability and alternating bending strength of shot peened AISI 4140", Zeitschrift für Metallkunde, vol. 93, no. 7, pp. 635-640. [30.11.-1].

[ 59 ] Obergfell, K.; Schulze, V. & Voehringer, O. (2002), "Neuartiger thermisch-mechanischer Versuchsstand", Materialprüfung, vol. 44, no. 4, pp. 139-143. [30.11.-1].

[ 60 ] Menig, R.; Schulze, V. & Voehringer, O. (2002), "Optimized warm peening of the quenched and tempered steel AISI 4140", Materials science and engineering A, vol. 335, no. 1, pp. 198-206. [30.11.-1].

[ 61 ] Menig, R.; Schulze, V. & Voehringer, O. (2002), "Residual stress stability and alternating bending strength of AISI 4140 after shot peening and successive annealing", Materials science forum, vol. 404, pp. 469-476. [30.11.-1].

[ 62 ] Horsch, C.; Schulze, V. & Loehe, D. (2002), "Konfokale Schneidkantenvermessung. Ermitteln der Topographie von Hartmetall-Schneidkanten", wt Werkstattstechnik online, vol. 92, pp. 609-611. [30.11.-1].

[ 63 ] Franz, C.; Hunkel, M.; Schulze, V.; Hoffmann, F.; Mueller, H. & Mayr, P. (2002), "Simulation der Eigenspannungen von Stahlbauteilen bei der Wärmebehandlung. Zwischenbericht über den Zeitraum vom 30.06.2001-30.06.2002", Forschungsreport, Forschungsvereinigung Antriebstechnik, vol. 2002, pp. 397I+II-1-397I+II-15. [30.11.-1].

[ 64 ] Schulze, V.; Lang, K.; Voehringer, O. & Macherauch, E. (1997), "Cyclic deformation behaviour of quenched and tempered AISI 414 at two-step tensile- compressive-loading", [30.11.-1].

[ 65 ] Auhorn, M.; Beck, T.; Schulze, V. & Loehe, D. (2002), "Quasi-static and cyclic testing of specimens with high aspect ratios produced by micro-casting and micro-powder-injection-moulding", Microsystem technologies, vol. 8, no. 2, pp. 109-112. [30.11.-1].

[ 66 ] Wick, A.; Schulze, V. & Voehringer, O. (2000), "Effects of warm peening on fatigue life and relaxation behaviour of residual stresses of AISI 4140 steel", [30.11.-1].

[ 67 ] Schulze, V. & Voehringer, O. (2000), "Influence of alloying elements on the strain rate and temperature dependence of the flow stress of steels", [30.11.-1].

[ 68 ] Peichl, A.; Huentrup, V.; Schulze, V.; Loehe, D. & Spath, D. (2000), "Einfluss des Wärmebehandlungszustandes auf die Mikrozerspanbarkeit von Stählen", [30.11.-1].

[ 69 ] Obergfell, K.; Schulze, V. & Voehringer, O. (2000), "Microstructural characterization of laser hardened steel surfaces", [30.11.-1].

[ 70 ] Obergfell, K.; Beck, T.; Schulze, V. & Loehe, D. (2000), "Mikroproben quasistatisch und zyklisch prüfen - Aufbau, Regelung und Meßwerterfassung einer Mikro-Universalprüfmaschine", [30.11.-1].

[ 71 ] Biermann, H.; Tetzlaff, U.; Grossmann, B. V.; Mughrabi, H. & Schulze, V. (2000), "Rafting in monocrystalline nickel-base superalloys induced by shot peening", [30.11.-1].

[ 72 ] Hoffmann, D.; Schulze, V. & Macherauch, E. (1996), "Modellierung des Verformungsverhaltens von praxisüblich nitriertem CK 20 bei Temperaturen 25 0C<=T<=590 0C", [30.11.-1].

[ 73 ] Burgahn, F.; Schulze, V.; Voehringer, O. & Macherauch, E. (1996), "Modellierung des Einflusses von Temperatur und Verformungsgeschwindigkeit auf die Fließspannung von Ck 45 im Tieftemperaturbereich T<=0.3Tsub(S)", [30.11.-1].

[ 74 ] Auhorn, M.; Kasanicka, B.; Beck, T.; Schulze, V. & Loehe, D. (2003), "Microstructure, surface topography and mechanical properties of slip cast and powder injection moulded microspecimens made of zirconia", Zeitschrift für Metallkunde, vol. 94, no. 5, pp. 599 - 605. [30.11.-1].

[ 75 ] Schulze, V.; Lang, K. & Macherauch, E. (2003), "Fatigue life and cyclic deformation behaviour of quenched and tempered steel AISI 4140 at two-step stress- and total-strain-controlled push-pull loading", Zeitschrift für Metallkunde, vol. 94, no. 5, pp. 492-498. [30.11.-1].

[ 76 ] Obergfell, K.; Schulze, V.; Loehe, D. & Voehringer, O. (2001), "Einfluss der Pulsfrequenz auf das temperaturkontrollierte Laserstrahlhärten von Stählen", Härterei-Technische Mitteilungen, vol. 56, no. 5, pp. 353-358. [30.11.-1].

[ 77 ] Obergfell, K.; Schulze, V.; Loehe, D. & Voehringer, O. (2001), "Application of x-ray diffraction analysis on microstructural investigations of laser-hardened steel surfaces", Zeitschrift für Metallkunde, vol. 92, no. 3, pp. 265-269. [30.11.-1].

[ 78 ] Menig, R.; Pintschovius, L.; Schulze, V. & Voehringer, O. (2001), "Depth profiles of macro residual stresses in thin shot peened steel plates determined by X-ray and neutron diffraction", Scripta Materialia, vol. 45, no. 8, pp. 977-983. [30.11.-1].

[ 79 ] Franz, C.; Hunkel, M.; Schulze, V.; Hoffmann, F.; Mueller, H. & Mayr, P. (2001), "Simulation der Eigenspannungen von Stahlbauteilen bei der Wärmebehandlung. Zwischenbericht über den Zeitraum vom 01.01. - 30.06.2001", Forschungsreport, Forschungsvereinigung Antriebstechnik e.V., vol. 2001, pp. 397I+II1-397I+II-18. [30.11.-1].

[ 80 ] Schulze, V.; Lang, K.; Voehringer, O. & Macherauch, E. (1998), "Versuchsführungsbedingte Unterschiede im zyklischen Verformungsverhalten von vergütetem 42 CrMo 4 bei Spannungs- und Totaldehnungskontrolle", [30.11.-1].

[ 81 ] Schulze, V.; Voehringer, O. & Macherauch, E. (1998), "Modellierung des Verformungsverhaltens und der Makrospannungsänderungen von kugelgestrahltem 42CrMo4", [30.11.-1].

[ 82 ] Holzapfel, H.; Wick, A.; Schulze, V. & Voehringer, O. (1998), "Einfluß von Kugelstrahlparametern auf die Randschichteigenschaften von 42CrMo4 in verschiedenen Wärmebehandlungszuständen", [30.11.-1].

[ 83 ] Holzapfel, H.; Schulze, V. & Voehringer, O. (1998), "Residual stress relaxation in an AISI 4140 steel due to quasistatic and cyclic loading at higher temperatures", [30.11.-1].

[ 84 ] Wick, A.; Schulze, V. & Voehringer, O. (1999), "Kugelstrahlen bei erhöhter Temperatur mit einer Druckluftstrahlanlage", [30.11.-1].

[ 85 ] Schulze, V.; Burgahn, F.; Voehringer, O. & Macherauch, E. (1993), "Zum thermischen Abbau von Kugelstrahl- Eigenspannungen bei verguetetem 42 CrMo 4", [30.11.-1].

[ 86 ] Schwarzer, J.; Schulze, V. & Vöhringer, O. (2003), "Evaluation of the influence of shot peening parameters on residual stress profiles using finite element simulation", Materials science forum, vol. 426, pp. 3951-3956. [30.11.-1].

[ 87 ] Schulze, V. (2003), "Warm peening. A possibility to induce stabilized compressive residual stresses", Metal finishing news, vol. 4, pp. 18-19. [30.11.-1].

[ 88 ] Obergfell, K.; Schulze, V. & Vöhringer, O. (2003), "Classification of microstructural changes in laser hardened steel surfaces", Materials science and engineering / A, vol. 355, pp. 348-356. [30.11.-1].

[ 89 ] Obergfell, K.; Schulze, V. & Vöhringer, O. (2003), "Simulation of phase transformations and temperature profiles by temperature controlled laser hardening: influence of properties of base material", Surface engineering, vol. 19, no. 5, pp. 359-363. [30.11.-1].

[ 90 ] Mikovic, T.; Schulze, V.; Löhe, D. & Vöhringer Otmar, . (2003), "Experimentelle Analyse und Modellierung des Kurzzeitumwandlungsverhaltens von Stählen am Beispiel von 42CrMo4", Härterei-Technische Mitteilungen, vol. 58, no. 6, pp. 304-313. [30.11.-1].

[ 91 ] Menig, R.; Schulze, V. & Vöhringer, O. (2003), "Kugelstrahlen und anschließendes Auslagern. Steigerung der Eigenspannungsstabilität und der Wechselfestigkeit am Beispiel von 42CrMo4", Härterei-Technische Mitteilungen, vol. 58, no. 3, pp. 127-132. [30.11.-1].

[ 92 ] Gerber, A.; Schulze, V. & Löhe, D. (2003), "Influence of selected manufacturing parameters on the fatigue strength and the damage behaviour of aluminium light weigth structures for automotive series production", Advanced engineering materials, vol. 5, no. 3, pp. 148-155. [30.11.-1].

[ 93 ] Franz, C.; Schulze, V.; Macherauch, E. & Löhe, D. (2003), "Simulation der Wärmebehandlung von Stählen am Institut für Werkstoffkunde I", Materialwissenschaft und Werkstofftechnik, vol. 34, no. 1, pp. 162-171. [30.11.-1].

Non-peer-reviewed papers at conferences

[ 1 ] Moch, K.; Dietrich, S. & Schulze, V. (2015), "Dependence of the local heat transfer coefficient on temperature and surface roughness in quenching steel parts in high efficiency quenching oil".

[ 2 ] Kümmel, J.; Gibmeier, J.; Müller, E.; Schneider, R.; Schulze, V. & Wanner, A. (2013), "Effect of built-up edges and transfer layers on the wear state during dry cutting of steel with cemented carbide tools".

[ 3 ] Klemenz, M.; Zimmermann, M.; Schulze, V. & Löhe, D. (2007), "Numerical Prediction of the Residual Stress State after Shot Peening". Numerical Prediction of the Residual Stress State after Shot Peening, eds. W. E. Nagel, pp. 437-448.
Abstract:
Shot peening is amechanical surface treatment with the purpose to modify the surface state of a meterial in order to improve fatigue strength of a component subjected to cyclic loading. Teh material state after a shot peening treatment is governed by various shot peening parameters. In order to comprehend the complex interaction between process parameters and material state time and money consuming experiments are usually accomplished. Promising alternatives are numerical simulation methods such as FEM combined with similarity mechanics having the possibility to predict the shot peening results for arbitrary combinations of shot peening parameters. In this work the residual stress development during shot peening for various shot peening parameters was simulated successfully with a FEM model. Additionally the method of similarity mechanics was used in combination with the FEM simulation results in order to predict residual stress states for a wide parameter field with almost no additional computing effort.


[ 4 ] Peichl, A.; Huentrup, V.; Schulze, V.; Spath, D. & Loehe, D. (2000), "Determination of heat treatment states fit for microcutting of steels". Verl. Ddp Goldenbogen, Dresden, pp. 976 - 979.

[ 5 ] Loehe, D.; Peichl, A.; Schulze, V.; Spath, D. & Tritschler, H. (2000), "Microcutting of steels - interaction of material properties and process parameters". VDE-Verl., Berlin, pp. 7 - 11.

[ 6 ] Menig, R.; Schulze, V.; Löhe, D. & Vöhringer, O. (2003), "Shot peening plus subsequent short-time annealing - a way to increase the residual stress stability and alternating bending strength of AISI 4140. > the residual stress stability and alternating bending strength of AISI 4140. Shot peening plus subsequent short-time annealing - a way to increase > the residual stress stability and alternating bending strength of AISI 4140". SAE, Warrendale (PA), pp. 711 - 718.

[ 7 ] Kasanická, B.; Schulze, V. & Löhe, D. (2003), "Characterisation of slip cast and powder injection moulded microcomponents made of zirconia". Frankfurt a.M..

[ 8 ] Auhorn, M.; Beck, T.; Schulze, V. & Löhe, D. (2003), "Determination of mechanical properties of micro-specimens produced by micro-moulding techniques". Rhiem, Voerde, pp. 35-39.

[ 9 ] Auhorn, M.; Beck, T.; Schulze, V. & Löhe, D. (2003), "Determination of mechanical properties of microspecimens made of a AuAgCu-alloy".

Non-peer-reviewed articles in books and monographic series

[ 1 ] Pabst, R.; Schulze, V. & Nestler, B. (2010), Graduiertenkolleg 1483, Prozessketten in der Fertigung, Shaker Verlag, Aachen. ISBN/ISSN: 978-3-8322-9036-8
Abstract:
In den letzten Jahren ist die Bedeutung der Simulation in der Fertigungstechnik gewachsen. Strategien zur Simulation einzelner, isolierter Fertigungsprozesse sind bereits weit entwickelt und vielfach erfolgreich umgesetzt. Jetzt gilt es die einzelnen Simulationsschritte verknüpfbar zu machen, um vollständige Prozessketten vom Halbzeug zum Bauteil zuverlässig simulieren zu können. Daraus ergibt sich die zentrale Forschungsidee des Graduiertenkollegs 1483, Simulationsmethoden zur Beschreibung, Bewertung und Optimierung von Bauteilzuständen bei verketteten Fertigungsprozessen zu entwickeln und durch experimentelle Untersuchungen zu verifizieren.

In einer weiteren Großinitiative fördert die Landesstiftung Baden-Württemberg Forschungsarbeiten im Rahmen eines Exzellenzzentrums CCMSE - Center of Computational Materials Science and Engineering. Die Ziele des CCMSE fokussieren sich auf die Erarbeitung von effizienten Simulationstechniken zur skalenübergreifenden Modellierung von Mikrostrukturausbildungen und zur Prozessschrittübergreifenden Beschreibung von Material- und Bauteilbearbeitungen. Auf der Basis umfangreicher Simulationsrechnungen werden Gefüge-Eigenschaftskorrelationen hergeleitet und Methoden zur Optimierung von Materialeigenschaften und Prozessabläufen für die Herstellung und Fertigung von Werkstoffen entwickelt. Die hergeleiteten Strukturbildungsmechanismen lassen sich auf verschiedene Materialsysteme übertragen. Mit den entwickelten Simulationsmethoden für die Material- und Werkstoffentwicklung soll eine Brücke zwischen universitärer und industrieller Forschung geschlagen werden. Die vorgestellten Forschungs- und Entwicklungsprojekte werden u. a. durch Mittel der Deutschen Forschungsgemeinschaft (DFG) und durch die Europäische Union, den Europäische Fonds für Regionale Entwicklung und das Land Baden-Württemberg gefördert.



[ 2 ] Schneider, M.; Köhler, G.; Fleischer, J.; Munzinger, C. & Schulze, V. (2011), "Genauigkeitssteigerung der Profilherstellung durch fliegendes Abtrennen während des Rundens beim Strangpressen" in Integration von Umformen, Trennen und Fügen für die flexible Fertigung von leichten Tragwerkstrukturen - Ergebnisbericht der Phase II, 1. Januar 2007 bis 31. Dezember 2010, eds. Tekkaya, E. & Baier, H., VDI-Verlag GmbH, Düsseldorf, pp. 73-100. ISBN/ISSN: 978-3-18-367802-0
Abstract:
Die flexible Herstellung dreidimensional gerundeter Strangpressprofile ist mit standardisierten Herstellverfahren für kleine Serien nicht umsetzbar. Im Sonderforschungsbereich Transregio 10 werden daher, basierend auf dem flexiblen Verfahren des Rundens beim Strangpressen, im Teilprojekt A4 Methoden und die erforderliche Maschinentechnik erarbeitet, um während des Run-dens eine rückwirkungsfreie Unterstützung des Profils im Raum, das Abtrennen desselben und die Übergabe an weitere Bearbeitungsstationen darzustellen. Eine zentrale Herausforderung ist dabei die Gewährleistung einer hohen Profilkonturgenauigkeit. Ausgehend von dem erarbeiteten Prototyp zum fliegenden Abtrennen soll ein Verfahren entwickelt werden, um die prozess- sowie temperaturbedingten Einflüsse auf die Konturgenauigkeit auszugleichen.


[ 3 ] Schulze, V. & Ruhs, C. (2012), "Prozessübergreifende Abtragregelung für die Mikrobahnerosion durch die Nutzung konfokaler Weißlichtsensorik" in Jahrbuch Optik und Feinmechanik 2012, OPTIK-Verlag Dr. Wolf-Dieter Prenzel, Görlitz, pp. 239-245. ISBN/ISSN: 978-3-7949-0831-8
Abstract:
Die Mikrostrukturtechnik ist mittlerweile ein bedeutender Markt mit einer hohen Nachfrage nach Bauteilen und Systemen mit Strukturdetails im Mikrobereich. Die voranschreitende Miniaturisierung sowie steigende Anforderungen an die Bauteilgüte und damit die Prozesssicherheit führen zu neuen Herausforderungen hinsichtlich der Optimierung des Fertigungsprozesses. Um große Stückzahlen bei gleichzeitig niedrigen Kosten zu realisieren, werden hoch belastbare Mikrobauteile normalerweise mittels Pulvermetallurgie wie dem Powder Injection Moulding (PIM) hergestellt. Zur Gewährleistung einer hohen Lebensdauer dieser Formwerkzeuge werden diese vorwiegend aus verschleißfesten Materialien, wie z. B. gehärteten Stählen, gefertigt. Der berührungslose und auf dem thermischen Abtragprinzip basierende Prozess der Mikrofunkenerosion bietet eine herausragende gestalterische Freiheit bei der Spritzgussformherstellung und ist im Stande, selbst härteste Werkstoffe zu bearbeiten.


[ 4 ] Tillmann, A.; Weckenmann, A.; Hartmann, W.; Schmidt, H.; Schulze, V. & Stockey, S. (2012), "Funktionsorientierte Bewertung bei der Druckwalzenherstellung" in Merkmalbasiert geregelte Fertigungsprozesse für die beherrschte Herstellung funktionaler Produkteigenschaften von mikrostrukturierten Bauteilen - Ergebnisbericht FunkProMikro, eds. Wiedenhöfer, T., Apprimus Verlag, Aachen, pp. 57-76. ISBN/ISSN: 978-3-86359-087-1
Abstract:
Bei der Fertigung von Werkstücken sind Abweichungen von der Soll-Gestalt und ungewollte Einflüsse des Produktionsprozesses auf die Oberfläche unvermeidlich. Wesentlich für das Ergebnis ist jedoch, dass das gefertigte Werkstück seine vorgesehene, geplante Funktion erfüllt. Bestehende Kennwerte und Toleranzkonzepte beschränken sich bisher lediglich auf Gestaltkenngrößen und deren Prüfung. Vor diesem Hintergrund hat sich das Verbundprojekt FunkProMikro folgende Ziele gesetzt:
  • Beschreibung funktionsbedingt zu fordernder Gestaltabweichungen
  • simulationsunterstützte Vorausbestimmung zu erwartender funktionaler Qualität
  • Identifikation funktionsorientiert signifikanter geometrischer Merkmale
  • Extraktion von Parametern für die Fertigungsprozesslenkung
Im Fokus der Betrachtung sollten Mikrostrukturen und mikrostrukturierte Bauteile stehen.


[ 5 ] Schulze, V. & Zanger, F. (2012), "Untersuchung der Zerspanung von Metall-Matrix-Verbundwerkstoffen (MMC) mittels Finite-Elemente-Simulationen" in Spanende Fertigung, eds. Biermann, D., Vulkan-Verlag GmbH, Essen, pp. 51-58. ISBN/ISSN: 978-3-8027-2965-2
Abstract:
Am wbk- Institut für Produktionstechnik wurde eine Methode für die FE-Zerspanungssimulation mehrphasiger Werkstoffmaterialien auf Mikroebene entwickelt und hier vorgestellt. Dazu wurden zwei verschiedene Werkstoffe mit unterschiedlichen Materialmodellen implementiert. Die Spanbildung konnte mittels einer selbstentwickelten Neuvernetzung in ABAQUS/Standard realisiert werden. Die hier vorgestellten Ergebnisse zeigen, dass das Simulationsmodell für eine präzise Vorhersage der in den Prozesszonen wirkenden Spannungen, Deformationen, Temperaturen und der daraus an den Werkzeugen resultierenden Kräfte geeignet ist, sodass die Wechselwirkungen unterschiedlicher Prozessparameter und Geometriegrößen sowie der Werkstoffzusammensetzung auf die resultierenden mechanischen und thermischen Werkzeugbelastungen in weiteren Analysen untersucht und diskutiert werden können.


[ 6 ] Schulze, V.; Klotz, S. & Zanger, F. (2012), "Experimentelle Untersuchung von Bauteilschädigung und Werkzeugverschleiß bei der FVK-Bearbeitung" in Spanende Fertigung, eds. Biermann, D., Vulkan-Verlag, Essen, pp. 330-337. ISBN/ISSN: 978-3-8027-2965-2
Abstract:
In den vergangenen Jahren hat der Einsatz von faserverstärkten Kunststoffen (FVK) immer weiter an Bedeutung gewonnen. Als einer der Treiber dieser Weiterentwicklung hat die Automobilindustrie in der jüngsten Vergangenheit verstärkt den Leichtbau mit Faserverbundbauteilen fokussiert. Die Gründe hierfür liegen beispielsweise in immer höheren Anforderungen an den Umweltschutz und den erforderlichen Gewichtsreduktionen [1]. Die Faserverbundwerkstoffe sind hier mit ihrer besseren spezifischen Steifigkeit und Festigkeit den Metallen deutlich überlegen. Zudem können durch die gezielte Anpassung von Faserverläufen an die vorliegenden Lastpfade weitere Gewichtsreduktionen erfolgen. Bauteile aus Faserverbundwerkstoffen werden meist endkonturnah hergestellt. Aus fertigungstechnischen Gründen ist jedoch eine Nachbearbeitung, beispielsweise bei der Herstellung von Bohrungen, für die spätere Montage oder zur Fügestellenvorbereitung, erforderlich. In den Bereichen, in denen die Bauteile nachbearbeitet werden, werden die Faserverläufe jedoch wieder unterbrochen, was zu einer Schwächung der Bauteile führt. Durch ungünstige Bearbeitungskräfte bei der Bearbeitung entstehen zudem Schädigungen an den Randzonen des Bauteils, die dieses weiter schwächen. Das primäre Ziel bei der Nachbearbeitung von FVK-Bauteilen ist es daher, bearbeitungsinduzierte Schädigungen zu vermeiden. Der zunehmende Einsatz von Faserverbundwerkstoffen, auch in Bereichen der Großserienfertigung, erfordert jedoch auch neue Herstelltechnologien, welche die wirtschaftlichen Anforderungen der Serienfertigung berücksichtigen [1]. Neben der Fertigungsqualität gewinnen die Fertigungskosten bei der Bearbeitung von FVK zur Sicherung der Wettbewerbsfähigkeit immer mehr an Bedeutung. Daher sind neben geringen Schädigungen möglichst geringe Prozesskosten ebenfalls ein wichtiger Bestandteil für den wirtschaftlichen Serieneinsatz von Faserverbundwerkstoffen.


[ 7 ] Schulze, V. (2002), "Warm- und Spannungsstrahlen - Wege zur Erzeugung stabilisierter und erhöhter Druckeigenspannungen"

[ 8 ] Miokovic, T.; Obergfell, K.; Schulze, V. & Voehringer, O. (2002), "Mikrostrukturelle Charakterisierung lasergehärteter Randschichten und Entwicklung neuartiger Temperatur-Zeit-Regime für die gepulste Laserstrahlhärtung"

[ 9 ] Menig, R.; Schulze, V. & Voehringer, O. (2002), "Shot peening at elevated temperatures - influence of the material state of AISI 4140 on the fatigue strength"

[ 10 ] (2002).

[ 11 ] Auhorn, M.; Beck, T.; Schulze, V. & Loehe, D. (2002), "Fatigue behaviour of a micro-cast Au-Ag-Cu alloy"

[ 12 ] Wick, A.; Schulze, V. & Voehringer, O. (2000), "Influence of the shot peening temperature on the fatigue strength and relaxation behaviour of residual stresses during cyclic bending of AISI 4140"

[ 13 ] Eigenmann, B.; Schulze, V. & Vöhringer, O. (1994), "Surface residual stress relaxation in steels by thermal or mechanical treatment"

[ 14 ] Obergfell, K.; Schulze, V. & Voehringer, O. (2000), "Modelling and experimental investigation of laser hardened steel surfaces"

[ 15 ] Biesinger, F.; Soehner, J.; Schulze, V.; Voehringer, O. & Weule, H. (2000), "Zerspankraftmessung und Randschichtcharakterisierung beim Hochgeschwindigkeits-Stirnplanfräsen"

[ 16 ] Biesinger, F.; Schulze, V. & Voehringer, O. (2000), "Characterization of HSC-milled surfaces"

[ 17 ] Schulze, V. & Voehringer, O. (1996), "Constitutive relation on the strain rate and temperature dependence of the flow stress of uniaxially deformed steels"

[ 18 ] Holzapfel, H.; Schulze, V.; Voehringer, O. & Macherauch, E. (1996), "Stability and relaxation behaviour of shot peening induced residual stresses in AISI 4140 during bending fatigue"

[ 19 ] Holzapfel, H.; Schulze, V.; Voehringer, O. & Macherauch, E. (1996), "Relaxation behaviour of shot peening induced residual stresses in AISI 4140 due to quasistatic uniaxial loading at elevated temperatures"

[ 20 ] Hoffmann, D.; Schulze, V. & Macherauch, E. (1996), "Modellierung des Verformungsverhaltens eines unlegierten Stahles mit Stickstoffkonzentrationsgradient bei Temperaturen 25 0C<=T<=590 0C"

[ 21 ] Schulze, V.; Lang, K. & Macherauch, E. (1995), "Ein- und mehrstufige totaldehnungs- und spannungskontrollierte Wechselverformungsexperimente an einem Stahl vom Typ 42CrMo4 unter Eigen- und Mittelbeanspruchungsvariation"

[ 22 ] Holzapfel, H.; Schulze, V. & Voehringer, O. (1995), "Relaxation of residual stresses - some new results"

[ 23 ] Schulze, V.; Lang, K.; Voehringer, O. & Macherauch, E. (1996), "Relaxation of shot peening induced residual stresses in quenched and tempered steel AISI 4140 due to uniaxial cyclic deformation"

[ 24 ] Schulze, V.; Voehringer, O. & Macherauch, E. (1993), "Thermal relaxation of shot peening induced residual stresses in a quenched and tempered steel 42CrMo4"

[ 25 ] Wick, A.; Schulze, V. & Voehringer, O. (1999), "Einsatz modifizierter Kugelstrahlbehandlungen zur Erhöhung der Schwingfestigkeit von 42 Cr Mo 4"

[ 26 ] Wick, A.; Schulze, V. & Voehringer, O. (1999), "Shot peening and stress peening of AISI 4140 at increased temperatures"

[ 27 ] Wick, A.; Schulze, V. & Voehringer, O. (1999), "Influence of the shot peening temperature on the relaxation behaviour of residual stresses during cyclic bending"

[ 28 ] Wick, A.; Holzapfel, H.; Schulze, V. & Voehringer, O. (1999), "Effect of shot peening parameters on the surface characteristics of differently heat treated AISI 4140"

[ 29 ] Wick, A.; Schulze, V. & Loehe, D. (1999), "Influence of heat treatment state on material changes close to surface of micromachined steel SAE 1045"

[ 30 ] Obergfell, K.; Schulze, V. & Voehringer, O. (1999), "Mikrostrukturelle Charakterisierung und Simulation lasergehärteter Randschichten von Stählen"

[ 31 ] Obergfell, K.; Schulze, V.; Lang, K. & Loehe, D. (1999), "Aufbau, Regelung und Messwerterfassung einer Mikro-Universalprüfmaschine"

[ 32 ] Soehner, J.; Weule, H.; Biesinger, F.; Schulze, V. & Voehringer, O. (2001), "Examinations and 3 D-simulations of HSC face milling process"

[ 33 ] Schulze, V.; Hornung, A.; Dahmen, N.; Hierl, F.; Tuerk, M. & Piotter, V. (2001), "Entbinderung pulverspritzgegossener Bauteile mit überkritischem Kohlendioxid"

[ 34 ] Schulze, V. & Voehringer, O. (2001), "Plastic deformation: constitutive description"

[ 35 ] Menig, R.; Wick, A.; Schulze, V. & Voehringer, O. (2001), "Neuere Untersuchungen zum Eigenspannungsabbau von Stählen"

[ 36 ] Gerber, A.; Schulze, V. & Loehe, D. (2001), "Automated welding of extruded profiles and sheets of aluminium alloys for car bodies"

[ 37 ] Biesinger, F.; Thiel, M.; Schulze, V.; Voehringer, O.; Krempe, M. & Wendt, U. (2001), "Characterization of surface and subsurface regions of HSC-milled steel"

[ 38 ] Biesinger, F.; Soehner, J.; Schulze, V.; Voehringer, O. & Weule, H. (2001), "Aspects of materials science and production engineering at high-speed-cutting processes and their finite-element simulation"

[ 39 ] Auhorn, M.; Beck, T.; Schulze, V. & Loehe, D. (2001), "Mechanical testing of specimens with high aspect ratios produced by micro-casting and micro-powder-injection-molding"

[ 40 ] Obergfell, K.; Schulze, V. & Voehringer, O. (1998), "Microstructural characterization of surface hardened 20MoCr4 steel (AISI 4118) using a pulsed Nd:YAG laser"

[ 41 ] Holzapfel, H.; Schulze, V.; Voehringer, O. & Macherauch, E. (1998), "Residual stress relaxation in a quenched and tempered steel due to quasistatic and cyclic loading at higher temperatures"

[ 42 ] Ehlers, M.; Schulze, V.; Mueller, H. & Loehe, D. (1998), "Numerical simulation of temperature, phase and stress evolution during immersion cooling of tempering steel"

[ 43 ] Schwarzer, J.; Schulze, V. & Vöhringer, O. (2003), "Finite element simulation of shot peening. A method to evaluate the influence of peening parameters on surface characteristics" in Shot peening. Hrsg.: L. Wagner, Wiley-VCH, Weinheim, pp. 508-515. ISBN/ISSN: 3-527-30537-8

[ 44 ] Schulze, V. (2003), "Characteristics of surface layers produced by shot peening" in Shot peening. Hrsg.: L. Wagner, Wiley-VCH, Weinheim, pp. 145-160. ISBN/ISSN: 3-527-30537-8

[ 45 ] Menig, R.; Schulze, V. & Vöhringer, O. (2003), "Influence of optimized warm peening on residual stress stability and fatigue strength of AISI 4140 in different material states" in Shot peening. Hrsg.: L. Wagner, Wiley-VCH, Weinheim, pp. 317-323. ISBN/ISSN: 3-527-30537-8

[ 46 ] Menig, R.; Schulze, V. & Vöhringer, O. (2003), "Residual stress relaxation and fatigue strength of AISI 4140 under torsional loading after conventional shot peening, stress peening and warm peening" in Shot peening. Hrsg.: L. Wagner, Wiley-VCH, Weinheim, pp. 311-316. ISBN/ISSN: 3-527-30537-8

[ 47 ] Menig, R.; Schulze, V. & Vöhringer, O. (2003), "Effect of short-time annealing on fatigue strength of shot peened AISI 4140 in a quenched and tempered material state" in Shot peening. Hrsg.: L. Wagner, Wiley-VCH, Weinheim, pp. 331-337. ISBN/ISSN: 3-527-30537-8

[ 48 ] Menig, R.; Schulze, V. & Vöhringer, O. (2003), "Comparison of surface characteristics and thermal residual stress relaxation of laser peened and shot peened AISI-4140" in Shot peening. Hrsg.: L. Wagner, Wiley-VCH, Weinheim, pp. 498-504. ISBN/ISSN: 3-527-30537-8

[ 49 ] Lang, K.; Schulze, V. & Vöhringer, O. (2003), "Shot peening and fatigue strength of steels" in Shot peening. Hrsg.: L. Wagner, Wiley-VCH, Weinheim, pp. 281-294. ISBN/ISSN: 3-527-30537-8

[ 50 ] Kasanická, B.; Wild, M.; Schulze, V. & Löhe, D. (2003), "Analysis of residual stresses in injection moulded micro bending specimens made of zirconia" in HASYLAB Annual report. Hamburger Synchrotronstrahlungslabor HASYLAB am Deutschen Elektronen-Synchrotron DESY. Hrsg.: G. Falkenberg, HASYLAB, Hamburg.