Measurement of residual stress distribution on coarse-grained polycrystalline materials by means of imaging plate
Sasaki Toshihiko; Yazawa Kazumichi; Hirose Hajime
Abstract:In this paper, a method for determining the distribution of residual stress on the surface of a coarse-grained material was studied. The method used in this study was a combination of the method based on the cos alpha method with an imaging plate (IP-cosa method) and the computerized tomography (CT). In the present method, mean stresses over many different irradiated linear area are measured using the IP-cosa method first. Second, the distribution of stress on the surface of the material is reconstructed through the CT approach. A method for determining the least distance, which is needed to obtain mean stresses accurately was also studied and the fractal analysis was applied to diffraction image for this purpose. An experiment was performed using a steel which consisted of grains having diameter around 200 mm. It was found from the experiment that the distribution obtained from the present method almost agreed with that obtained from the sin2y method using both the parallel beam and the oscillation methods. The present method has a feature that the measurement is easier because the analytic method for polycrystalline materials can be used. In principle, the method is applicable to more coarse-grained materials as long as the material is large enough to keep the irradiated area more than the least distance and thus it will be useful to obtain actual residual stress state on coarse-grained materials. Key Words:Nondestructive inspection, X-ray stress measurement, Imaging plate, Computerized tomography, Residual stress, Coarse-grained mateirial, Fractal analysis