Development of X-ray stress measurement technique to achieve accurate evaluation for strength of polygranular graphite

A polygranular graphite consists of graphite crystallites. A graphite has strong elastic and strength anisotropy due to its crystal structure, especially in-plane and out-of-plane directions. To reveal mechanical behavior in several directions, stress measurements in several directions are required. In this study, to realize the measurements, a ψ-diffraction X-ray stress measurement system was developed that is equipped a cradle stage onto the current Ω-diffraction X-ray stress measurement system. This system can measure diffractions from 004 indices The measurements using Ω-diffraction X-ray stress measurements were also conducted for the measurements of several directions. Stress measurements were performed during applying stress by four-point bending or uniaxial compressing on the specimens. The relationship between applied macroscopic stress and measured stress by X-ray stress measurement, which corresponds to elastic lattice strain in each crystal direction, were revealed.