On-the-Fly Fast X-Ray Tomography Using a CdTe Pixelated Detector—Application in Mechanical Testing

Abstract

Fast tomography measurements are still done almost exclusively within the domain of synchrotrons. However, recent progress in radio diagnostic instrumentation has enabled researchers to perform time-lapse computed tomography (4-D CT) even under laboratory conditions with standard X-ray sources. Thus, fast time-dependent processes within materials with relatively high X-ray attenuation can be monitored. This paper describes the in situ tomographic monitoring of crack formation and propagation in a quasi-brittle silicate matrix composite subjected to three-point bending. A 3-D CT volume containing the region of interest in the specimen is imaged over a period of time, while the continuously increasing load causes crack initiation and propagation, creating a dynamic volume data set. An acquisition time of 50 s for one full-angle tomography with 400 projections makes this tomographic system one of the fastest systems in the world. The resulting visualizations provide qualitative information concerning progressive crack propagation within areas of lower material density. Differential images then allow displaying the spatial orientation of the crack over time. The results were further processed for a quantitative analysis of image quality using various methods of beam hardening correction.