Procedures for Residual Stress Analysis in Textured and in Coarse Grained Materials

Abstract

For the investigation of residual stresses by means of X-ray diffraction, special procedures for the registration and evaluation of the experimental strain data are necessary for textured and coarse grained materials. In both cases inhomogeneous diffraction intensity patterns are present which lead to the formation of intensity poles or even to Bragg reflections. Such experimental findings indicate also that the material properties within the investigated gauge volume are anisotropic so that the evaluation of the experimental strain up to stress values requires the introduction of anisotropic elastic constants. For the residual stress investigation of textured and fine grained materials averaging procedures using short wavelength radiation are discussed. A more detailed insight also in the microstress states may be obtained from the measurement of several different reflections whereby the effects of the elastic anisotropy may be corrected for by including the orientation distribution function as calculated from different poles figures. For coarse grained materials it is experimentally possible to determine the strain state of the individual crystallites so that their anisotropy is directly included in the evaluation of the stress data by using the single crystal elastic constants. The macroscopic residual stress values may then be obtained from the averaging over stress values of several crystallites.