| [ 1 ]
|| Schild, L.; Kraemer, A.; Reiling, D.; Wu, H. & Lanza, G. (2018), Influence of surface roughness on measurement uncertainty in Computed Tomography. 8th Conference on Industrial Computed Tomography, Hrsg. NDT Online, S. 1-8.
In geometrical measurements using computed tomography (CT), the measurement uncertainty is often derived from reference measurements that have been made with a tactile coordinate measuring machine (CMM). This paper shows the influence that a test object’s surface roughness has on such reference measurements. To do so, test objects which have been manufactured by means of additive manufacturing methods are compared to conventionally produced objects. Results of geometrical measurements using a tactile CMM as well as measurements conducted with a CT are analysed with respect to the surface quality. Following the analysis, the validity of tactile CMMs to reference CT measurements is discussed.
| [ 2 ]
|| Schild, L.; Vötter, L.; Jung, M.; Häfner, B. & Lanza, G. (2018), Aufwandsarme Unsicherheitsstudien in der industriellen Computertomographie, wt - Werkstatttechnik Online, S. 1-9.
Zum Erreichen einer minimalen Messunsicherheit ist es in der industriellen Computertomographie (CT) nötig, der Messaufgabe angemessene Einstellungen zu wählen. Aufgrund der vielfältigen Einstellmöglichkeiten müssen die richtigen Einstellungen langwierig durch systematische Variation ermittelt werden. Dieser Artikel schlägt unter Berücksichtigung der CT-spezifischen Eigenheiten ein Vorgehen vor, wie solche Unsicherheitsstudien mit einem möglichst geringen Aufwand realisiert werden können.
| [ 3 ]
|| Schild, L.; Häfner, B. & Lanza, G. (2018), Knowledge Based User Support for Computed Tomography Measurements. Advances in Production Research: Proceedings of the 8th Congress of the German Academic Association for Production Technology (WGP), Aachen, November 19-20, 2018, Hrsg. Springer Nature Switzerland AG, S. 667-678.
X-Ray Computed Tomography (CT) has been successfully introduced into industrial applications in the last few years. Recent industrial needs aim at increasing the accessibility of CT technology to more users than only measurement experts. Suitable concepts for user support have been developed in the past. However, these user support concepts do not cover the entire measurement process and only a small variety of measurement tasks. To overcome these shortcomings and to support the user in an optimal manner, the existing concepts need to be integrated together with knowledge deduced from different measurements into a single software tool. In this paper, different types of knowledge based systems are compared and assessed in their ability to integrate knowledge of the measurement process, the form and material of the workpiece as well as quality parameters of the CT projections. The assessment is used to derive the structure of a suitable knowledge based system that addresses industrial needs regarding flexibility and usability. The results may be used in the future to develop a software tool for user support, which can be used in an industrial environment, enabling untrained users to utilize CT-based systems with a low measurement uncertainty.
| [ 4 ]
|| Schild, L.; Fülling, M.; Häfner, B. & Lanza, G. (2019), Uncertainty Evaluation of Pore Analysis for Additively Manufac-tured Parts using Cross Sections. 9th Conference on Industrial Computed Tomography, Hrsg. NDT Online, S. 1-8.
Additively manufactured (AM) workpieces, which have been produced by means of laser beam melting (LBM), tend to show quality relevant pores and cracks on the inside. Quality assurance on these parts may be conducted using x-ray Computed Tomography (CT), as CT is able to spot pores and cracks in the entire volume of a specimen. However, the uncertainty of detection of such cavities in a CT measurement is unknown. To tackle this shortcoming, different authors have compared metallographic cross sections to CT images. None of these investigations have compared the cross section’s plane directly to the corresponding plane of the CT’s 3D voxel image, without using features of the CT image itself, though. This paper introduces a special artifact as reference standard, whose pyramid like form allows a direct comparison of a metallographic cross section and the corresponding plane in a CT scan. The shape of the test object allows to calculate the parameters of the plane equation of the metallographic cross section in a coordinate system fixed to the test object. The plane equation is used to identify and investigate the corresponding plane in the CT scan. By comparing this artificial cross section from the CT scan with the cross section from the metallography specimen, the CT’s performance for detecting pores is assessed. As a result, a general method to test any CT’s capability to detect pores in an AM part is given by using cross sections of test objects with the proposed pyramid like form.