The Effect of Setting Errors on the Accuracy of Stress Measured with Parallel Beam X-Ray Diffractometer

Abstract

In the X-ray stress measurement using a parallel beam diffractometer, the X-ray diffraction profile was approximately calculated by digital computer, assuming some setting errors, i.e. the offset of the specimens or incidental X-ray beams against the center of the scanning circle of X-ray detector. The incidence angle φ used were 0°, 15°, 30° and 45°. The effects of setting errors on the accuracy of stress determined by the sin2φ method were examined using peak angles of the calculated diffraction profile.The relations between the peak angle and the offset of the specimens, obtained from the calculated diffraction profile, showed good correlation with those obtained from the experiment. The calculated diffraction peak angles, when the offset of the specimens or incidental X-ray beams is assumed showed cyclic changes in relation to the divergence angle α of the receiving soller slit.It seems unavoidable, even under the most careful setting, that the error of the stress of Fe {211} determined by Cr-Kα amounts to ±2kg/mm2, where α=0.35°.Provided, on the contrary, that the error of the determined stress is allowable up to ±2kg/mm2, the offset of the specimens or incidental beams against the center of the scanning circle is acceptable up to ±4mm or ±3mm respectively.