Fundamental Concepts in X-ray Diffraction

Abstract

Diffraction methods of residual stress determination basically measure the angles at which the maximum diffracted intensity occur when a crystalline sample is irradiated with x-rays or neutrons. From these angles one then obtains the spacing of the diffracting lattice planes by using Bragg’s law. If the material is under load, these values will be different than the unstressed plane spacing, and the difference will be proportional to the stress acting on the planes. At this point one can use elasticity theory, Is discussed in Chap. 2 and 3, to determine the stress (residual or applied) acting on these planes. Thus, no matter how sophisticated the elasticity analysis, the final stress results are only as good as the data supplied by the diffraction methods.