Comparison of warm laser shock peening and laser shock peening techniques in lengthening the fatigue life of welded joints made of aluminum alloy

Welded joints made of 6061-T6 Al alloy were studied to evaluate warm laser shock peening (WLSP) and laser shock peening (LSP) processes. The estimation model of laser induced surface residual stress was examined by means of experiments and numerical analysis. The high-cycle fatigue lives of welded joint specimens treated with WLSP and LSP were estimated by conducting tensile fatigue tests. The fatigue fracture mechanisms of these specimens are studied by surface integrity and fracture surface tests. Experimental results and analysis indicated that the fatigue life of the specimens processed by WLSP was higher than that with LSP. The large increase in fatigue life appeared to be the result of the larger residual stress, more uniform microstructure refinement and the lower surface roughness of the WLSP specimens.