X-ray residual stress measurement under non-ideal conditions using silicon-on-insulator pixel detectors

We report the application of charge-integration-type silicon-on-insulator (SOI) pixel detectors, INTPIX4 and INTPIX4NA, to X-ray residual stress measurements under non-ideal conditions. Although these devices can measure residual stress in less than 1 s, they have been evaluated for only flat surfaces under ideal conditions. In this study, we examined their applicability to curved surfaces and verified their measurement accuracy for imperfect diffraction rings. The cos(α) and Fourier analysis methods were used for residual stress evaluation. The measurement results showed that the stress measurement on curved surfaces is possible when the ratio of the X-ray irradiation diameter to the specimen diameter is less than 0.5 in the circumferential stress direction. In the case of imperfect diffraction rings, residual stress measurement is possible if a detection range of at least 20°–30° is obtained for the diffraction rings of materials with good crystallinity. Furthermore, an X-ray intensity of approximately 5 W was sufficient for residual stress measurements, and the measurement accuracy can be improved using the plane oscillation method in the case of spotty diffraction rings. Residual stresses in steel with a diffraction ring with a full width at half maximum of 6.5° or less can be measured normally. The results provide insights into the applicability of the developed device to curved surfaces and samples with imperfect diffraction rings. We will conduct a comprehensive evaluation of metal products in our future work.