Transmission Imaging and Strain Mapping in the Vicinity of Internal Crack Tip Using Synchrotron White X-Ray
A transmission imaging and a strain mapping in the vicinity of a crack tip in steel were investigated using a high energy white X-ray obtained from BL28B2 beam line at SPring-8 in Japan. Low-alloy and high-tensile steel was used as a specimen prepared in the G-type geometry with a rectangular sectional part of 5mm thickness for a four-point bending. A fatigue crack was introduced into the notch root on the tension side of the specimen by a pulsating bending load. The imaging of the crack in the specimen under the bending load was carried out by using the CCD camera that can detect indirectly the X-ray transmitted through the specimen. To measure the internal strain in the vicinity of the crack tip, the synchrotron white X-ray beam, which had a height of 80m and a width of 300m, was incident on the specimen with the Bragg angle of 5 degrees using the energy dispersive X-ray diffraction technique. As the results, the transmitted image of the crack showed that the crack in the specimen was propagated deeper than that on the surface. The map of the internal strain near the crack tip could be obtained using the white X-ray with energy ranging from 50keV to 150keV. It became clear by the numerical simulation that the FWHM of diffracted X-ray profile measured near the crack tip was increased due to the steep change in the strain distribution. It was confirmed that the synchrotron white X-ray was useful for the imaging of the internal crack and the strain mapping near it.
T. Chandra, N. Wanderka, W. Reimers , M. Ionescu
J. Shibano et al., "Transmission Imaging and Strain Mapping in the Vicinity of Internal Crack Tip Using Synchrotron White X-Ray", Materials Science Forum, Vols. 638-642, pp. 2476-2481, 2010