A METHOD OF DETERMINING THE ELASTIC PROPERTIES OF ALLOYS IN SELECTED CRYSTALLOGRAPHIC DIRECTIONS FOR X-RAY DIFFRACTION RESIDUAL STRESS MEASUREMENT

A technique and apparatus are described for obtaining the elastic constant E/(1 + ν) in selected crystallographic directions for the purpose of calibrating x-ray diffraction residual stress measurement methods. The preparation of a simple rectangular beam specimen with two active electrical resistance strain gages applied to the test surface is described. Samples are clamped in a diffractometer fixture designed to minimize displacement errors, and loaded in four-point bending to several stress levels below the proportional limit. A method is described for calculating E/(1 + ν) and an estimate of the experimental error. Values of E/(1 + ν) obtained for several alloy-(hkl) combinations are presented. The results indicate that several alloys of current commercial interest exhibit significant elastic anisotropy.