Determination of Stress Gradients by X-ray Diffraction: Comparison of Different Methods and Applications

The paper presents a review of the main theoretical formulations of the analysis of steep stress gradients by X-ray diffraction and a comparison of calculations with experimentally applied stresses in a four-point bending test on a beryllium specimen. The comparison between theoretical approaches and experiments is therefore limited to uniaxial linear stress gradients. It shows that, in this case, only an evaluation of stress gradient can be obtained from the analysis of X-ray diffraction measurements even when experiments are performed very carefully. In this direction, very complex formulations could often not be necessary. Then, a summary of advantages and drawbacks of each theoretical approach is presented. Finally, for different forms of stress gradients, the paper proposes the most convenient formalism and experimental technique to be used.