Strengthening Effect Analysis of Laser Shock Processing on Aluminum Alloy Welded Joint Process

Abstract

High-strength aluminum alloy is one of the commonly used materials of pressure vessels. And it has the significant advantages of light-weight and cost-effective. But the strength of welded aluminum alloy greatly decreased. The welding line and heat-affected zone became high-risk area on pressure vessel. At present, it is difficult to improve the welding process, thus improving the microstructure and stress state of welded joints become the main means to improve the fatigue properties and extend the service time of aluminum pressure vessels. As a new treatment process after welding, the process parameters of laser shock processing (LSP) can be precisely controlled, and the process is non-contact. It can be adapted to deal with macro and micro scale aluminum pressure vessels, so it has broad prospects for engineering applications. Based on the introduction of principle and features of LSP welded joint process, the estimation model of laser-induced surface residual stress is analyzed. The safety lives of welded joint specimens with and without LSP are estimated by making low cycle tensile fatigue test. The effect of LSP on fatigue properties of aluminum alloy welded joint is analyzed. The fatigue fracture mechanisms of these specimens with and without LSP are studied by surface integrity and fracture surface testing. The result showed that the safety lives of these specimens with LSP are increased significantly. At the same time, Compressive residual stress and dense surface layer are induced at the surface of welded joints by LSP. After summarizing the research status about fatigue properties of aluminum alloy welded joint by LSP, the problems existing in current research of LSP welded joint process are pointed out. Finally, expectations of future studies on LSP welded joint process are brought forward.