Effects of residual stress induced by laser shock peening on mixed-mode crack propagation behavior in 7075-T6 aluminum alloy panel

The effects of residual stress on mixed-mode crack propagation behavior of 7075-T6 aluminum alloy panel subject to multiple laser shock peening (LSP) impacts were investigated. Residual stress was obtained by an efficient LSP simulation termed continuous explicit-dynamic impact strategy. A numerical method, combining finite element (FE) method and residual stress intensity factor (SIF) analysis, was used to predict the mixed-mode (I/II) crack propagation in peened compact tension shear (CTS) sample. The effects of residual stress on the mixed-mode crack behaviors in different coverage areas were analyzed. It was found that the LSP-induced residual stress can change the crack path. Compressive residual stresses increase the effective crack length, and delay the crack propagation. The increased LSP coverage area and the decreased distance from the treated area to the crack tip are beneficial to the fatigue performance. The obvious crack turning point near the peened area is related to the significant change of mode II SIF components (K_II^load and K_II^res). The proposed numerical method provides a new idea for the damage tolerance analysis with respect to the applications of LSP technology in aircraft structures.