Influence of Rebar Strength, Pre-treatment, and Measurement Method on Residual Stress Measurement using Portable X-ray Diffractometer

It is effective for the maintenance of existing structures to understand the current status, such as the residual stress of the materials used, and a portable X-ray diffractometer is used as a technique for measuring steel stress. Although measurement methods and pre-treatment for steel bars with low strength have been revealed, the influence of the strength on the X-ray stress measurement and the appropriate measurement method has not been clarified. In this study, residual stress measurements using the X-ray diffraction are performed on steel bars, the differences in the results for various steels with different strengths are discussed, and measurement conditions for accurate measurement are reported. In addition, the cause of the tendency of the X-ray stress measurement to be smaller than the actual increment value under high stress is investigated. The experimental results show that the appropriate measurement conditions vary depending on the rebar strength, and that the X-ray stress measurement under high stress also varies. The metallurgical structure of the steel was shown to be related to the cause of this phenomenon through microstructural observation and analysis of the deformation behavior.