X-ray Stress Measurement of Coarse-Grained Polycrystalline Materials by Imaging Plate Method

Abstract

We describe the applicability of the imaging plate method for determining stress by x-rays of coarse-grained materials. Three kinds of approach were examined. The first one was the standard type which adopted neither the software oscillation method, which is one of the image processing methods used to improve the accuracy of peak determination in the case of spotty diffraction rings due to coarse-grains, nor the mechanical oscillation method, in which the specimen is moved in a plane parallel to the surface of the specimen. The second one used the software oscillation method without the mechanical oscillation method. The third one used both the software and the mechanical oscillation methods. The material used for the experiment was steel of about 0.55% carbon content (JIS S55C). Specimens with grain size of about 5 μm, 50 μm, 100 μm or 200 μm were prepared by heat treatment such as quenching and annealing at different temperatures. From the experiment that used a collimator of 1 mm diameter, it was found that the standard method was useful for materials with grain size less than about 50 μm. Both measurement accuracy and applicable grain size were imporved by applying the second method. Although the limit of the applicable grain size was about 100 μm in the case of the second method, the third method was found to be able to increase the limit, and specimen with grain size of about 200μm was analyzed accurately by the third method. It is possible to measure stresses on materials with arbitrary grain size in principle using both the mechanical oscillation method and IP.