WEB Determination of the interface structural resolution of an industrial X-ray computed tomograph using varying gap sizes of a gauge block standardTuesday (22.09.2020) 16:10 - 16:25 Z: Special Symposia II Part of:
Industrial X-Ray computed tomography (XCT) is a tool for non-destructive testing and the only volumetric analysis method with the ability to quantify dimensions inside the component like crack expansions. However, the XCT is a relatively young technology in dimensional metrology and thus faces several challenges. Steel which is often used in joining processes, poses the computed tomography besides image quality influencing metal artefacts to further challenges. In order to illuminate this material a high current is necessary due to the strong material-dependent absorption. This leads to an increase of the focal spot and thus to the resolution of the computed-tomography, that is limited to the blur and the component magnification. Nevertheless, the characteristic of a component can only be detected if the magnification of the component is high enough that the characteristic is displayed on the detector image through several pixels and after the Feldkamp reconstruction through volume pixels. A wide range of structural resolution standards is used to assess the resolution of a X-Ray computed tomography. The determination of the metrological structural resolution (MRS) is possible through it. The MRS is the smallest reliable resolvable surface structure. Due to the fact that the relevance of the MRS for the determination of internal interfaces is not finally clarified, the interface structural resolution (ISR) has to be considered for the characterisation of an XCT system. The ISR is the smallest resolvable interface between two surfaces. The two-sphere standard according to Zanini and Carmignato allows the evaluation of the point-shaped transition between two spheres after the CT-reconstruction in form of a neck-shaped transition. This leads to the determination of the distances between the sphere surfaces and allows a statement about the ISR. The subproject C05 of Transregio 285 developed an interface structural resolution standard with a variable gap size. This consists of calibrated parallel gauge blocks. The standard has a higher number of probing points and thus a higher stability regarding to the fitting of the planes of the gauges through which the ISR is determined. The presentation compares the results of the computed tomography measurements for the designed interface structural resolution standard with those of the two-sphere standard according to Zanini and Carmignato.