Incremental Hole Drilling Residual Stress Measurement in Thin Aluminum Alloy Plates Subjected to Laser Shock Peening

The American standard ASTM E837 presents a standard procedure to determine residual stresses in isotropic materials using the incremental hole drilling technique (IHD). The standard, however, presents limitations regarding its applicability, such as those related with the thin thickness of the samples. According to this standard, in depth non uniform residual stresses can only be determined, roughly, in plates where the thickness is greater than the mean diameter of the strain gage rosette used. This limitation excludes important experimental cases and, therefore, deserves to be investigated. In this work this limitation is numerically and experimentally investigated in detail, considering the case of residual stresses induced by laser shock peening (LSP) in aluminum alloy 7075-T651 plates. The obtained results using the incremental hole drilling technique (IHD), based on the integral method, are benchmarked against the results of several diffraction techniques, used as reference, and a procedure to correct the experimentally determined strain-depth relaxation curves, to accurately still apply the ASTM E837 standard procedure is discussed and validated.