FORMALISM FOR THE EVALUATION OF STRONGLY NONLINEAR SURFACE STRESS-FIELDS BY X-RAY-DIFFRACTION PERFORMED IN THE SCATTERING VECTOR MODE

A formalism is proposed for the evaluation of residual stress fields in polycrystalline materials which vary significantly within the penetration depth tau of the X-rays. It is shown that the penetration depth may be varied independently of the angle psi by rotating the sample around the scattering vector g(psi psi) which is parallel to the normal of the reflecting lattice planes N-h. Therefore, it becomes possible to separate individual components of the stress tenser from the fundamental equation of X-ray stress analysis and to evaluate the gradients sigma(ij)(tau) without any assumption in form of an analytical expression to describe the depth profiles.