Issue 42

J. Klon et alii, Frattura ed Integrità Strutturale, 42 (2017) 161-169; DOI: 10.3221/IGF-ESIS.42.17 166 pair X-Ray tube – detector. For CT scanning, a nanofocus X-Ray tube (XWT-240-SE, X-Ray WorX, Germany) operating in microfocus mode (spot size 4.0 μm) with a voltage of 220 kV, target current of 386 μA and power output of 85 W was used. Low energy photons, which do not contribute to the resulting image quality, were filtered using a 1.5 mm thick layer of brass. As a detector, a flat panel (XRD-1622-AP-14, Perkin Elmer, USA) with dimensions of 40 × 40 cm, pixel matrix 2048 × 2048 and 200 μm pixel size operating with a capacity of 0.5 pF was used. By geometry adjustment to the focus- detector distance of 1000.09 mm and focus-object distance of 326.23 mm, the projection magnification factor 3.07 was obtained, leading to the resolution of 65.24 μm per pixel in projections and 65.86 μm per voxel in 3D reconstructions. Geometrical parameters were chosen in order to obtain the best possible resolution with regard to the size of the samples and the detector area. For image correction in projection images, standard “dark field” and “open beam” correction, along with “beam hardening” correction (BHC), was used. Data for BHC were taken for a set of brass filters with thicknesses of 0, 0.3, 0.6, 0.9, 1.5, 3.0 and 6.0 mm, the correction image for each filter was averaged out of fifty images with the acquisition time of 1000 ms. For tomography, 1 200 projections were acquired, each with the exposure time of 1000 ms. Figure 6 : Overall view of the test machine with the specimen and selected details of the experiment. Figure 7 : P–CMOD diagram of MCT A and MCT B tests.