Non-destructive Surface Residual Stress Profiling by Multireflection Grazing Incidence X-Ray Diffraction: a 7050 Al Alloy Study

Abstract

The multireflection grazing incidence X-ray diffraction method (MGIXD) was used to analyze the surface residual stresses in 7050 Al alloy samples. This technique can provide a non-destructive stress profile in function of sample depth, avoiding the relaxation effects intrinsic to destructive methods. The state of residual stress in aeronautical aluminium samples was modulated by milling and shot peening processes. After structural characterization, the residual stress states of the samples were analyzed by multireflection and conventional stress measurement methods. The milled samples presented tensile surface residual stress relaxation attributed to thermal effects and the shot peened samples showed strong compressive stress at sub-surface, which intensity was reduced near the surface. The residual stress profiles of the Al samples were obtained by MGIXD method that evidenced properties commonly undetected in conventional residual stress studies.