Japanese Standard for X-ray Stress Measurement

摘要

To authorize the use of X-rays in stress determination widely in the industrial fields, JSMS Committee on X-ray Study of Mechanical Behavior of Materials first established the Standard for X-ray Stress Measurement for ferritic steel and martensitic steel in 1973. This Standard has been widely adopted and effectively used in industrial as well as research fields in Japan to evaluate residual stresses in the parts and components of mechanical products and in other fields. The Standard is based on the sin~2ψ method, which approximates the plane stress in the X-ray irradiated region, and the use of parallel beam optics. Basically, a 2θ-sin~2ψ diagram is plotted in order to confirm the linearity of the line. From the slope of the regression line, the stresses are determined by the following equation: σ = KM where K is the X-ray stress constant and M is the slope of the 2θ-sin~2ψ diagram. A 211 diffraction line obtained by CrKα characteristic X-rays should be used to observe lattice distortions. It is recommended that the position of diffraction profile be determined by the FWHM method as it is the most accurate in determining the position when compared with other methods. It is noted that the Standard recommends the parallel beam optics which permits a few mm of setting error on the objective surface without any alteration in the evaluated stresses. This enables us to obtain a very easy and reliable way to measure the stress at a job site. The side inclination method (ψ-diffractometer method) was supplemented in the Standard in 1977. In 1982, the Standard was revised to include a method to measure austenitic steel by 311 CrKβ diffraction and also a digital evaluating method, made possible by advanced computer techniques in the measuring system. The newest version, which governs a position sensitive detector, was published in 1997. Cooperative research by the committee determined the X-ray stress constant K to be — 318 MPa/deg for the 211 CrKα diffraction of ferritic steel and martensitic steel and — 366 MPa/deg for the 311 CrKβ diffraction of austenitic steel.