Residual Stress Gradient Analysis by Multiple Diffraction Line Methods

The paper deals with methods for X-ray stress analysis (XSA), which allow for the evaluation of near surface in-plane residual stress gradients sigma(parallel to)(Or) and sigma parallel to(z) in the LAPLACE- and the real space, respectively. Since the 'robustness' of residual stress gradient analysis strongly depends on both, the quality of the measured strain data and the number of experimental data points, the discussion aims at those approaches which are based on processing various diffraction lines or even complete diffiaction patterns. It is shown that these techniques, which were originally developed for angle-dispersive (AD) diffiaction, can be adapted and enhanced for energy-dispersive (ED) diffraction employing high-energy synchrotron radiation. With the example of a shot-peened ferritic steel it is demonstrated, that sin(2)psi-data measured in the psi-mode of XSA employing the ED diffraction technique can be analyzed on different levels of approximation.