A Comparison of Finite Element Analysis With Neutron and X-Ray Measurements of Residual Strains in Stainless Steel

Abstract

The objective of the present work was to compare calculations of residual strain in a steel ring deformed under diametral loading in compression with bulk measurements made with neutron diffraction and surface measurements made with X-rays. Numerical analysis, carried out at LLNL using the NIKE finite element codes, showed that the distribution of residual strain at the four 90° positions of the ring were as expected for a plastically-bent plate. The sample had been designed initially to give plane stress conditions during deformation, and this result was confirmed by comparing calculations from NIKE2D and NIKE3D. Neutron diffraction measurements were made using the (111) and (002) diffraction lines. Both sets of results clearly delineated the elastic-plastic boundaries and the elastic core of the sample. However, because of the elastic anisotropy of the steel, the strains measured with (002) were greater, and those measured with (111) were less than predicted by the NIKE analysis. X-ray diffraction measurements were made with the (420) diffraction line, in order to obtain peaks at high backscattering angles. Results were in reasonable agreement with the NIKE calculations. The data will be discussed in terms of the choice of diffraction line and the elastic anisotropy of stainless steel.