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

For the investigation of residual stresses by means of X-ray diffraction, special procedures for theregistration and evaluation of the experimental strain data are necessary for textured and coarsegrained materials. In both cases inhomogeneous diffraction intensity patterns are present which leadto the formation of intensity poles or even to Bragg reflections. Such experimental findingsindicate also that the material properties within the investigated gauge volume are anisotropic sothat the evaluation of the experimental strain up to stress values requires the introduction ofanisotropic elastic constants. For the residual stress investigation of textured and fine grainedmaterials averaging procedures using short wavelength radiation are discussed. A more detailedinsight also in the microstress states may be obtained from the measurement of several differentreflections whereby the effects of the elastic anisotropy may be corrected for by including the orientationdistribution function as calculated from different poles figures. For coarse grained materials it isexperimentally possible to determine the strain state of the individual crystallites so that their anisotropyis 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 valuesof several crystallites.