The influence of multiaxial stress states, stress gradients and elastic anisotropy on the evaluation of (Residual) stresses by X-rays

In recent years, nonlinear d versus sin² ψ distributions have been observed in stressed materials which cannot be explained by the classical fundamentals of X-ray stress measurement, d is the interplanar spacing measured and ψ is the angle between the surface normal of the sample and the measuring direction. This paper reviews treatments for these nonlinear distributions, including stress gradients, shear stresses and anisotropic X-ray elastic constants. Methods for the evaluation of stresses are reported, and recommendations are given for the practical application of X-ray stress measurement.