PNNL

Abstract

This study uses hole-drilling electronic speckle pattern interferometry and process simulations to address three critical gaps in understanding 3D residual stress distributions in friction-stir-processed thin aluminum plates. First, a gradual stress reduction from the tool shoulder side to the bottom surface was revealed in AA7075. In AA380, the stresses sharply increased near the surfaces because of the skin effect. Additionally, increased process temperature reduced stress in AA380 but had the opposite impact in AA7075 due to its higher yield stress. Finally, stresses increased with an additional AA380 pass, a phenomenon attributed to material hardening occurring in the initial pass.