The residual stress distribution and fatigue property of TC4 laser-welded joint treated by laser shock peening

Abstract

The absence of highly tensile residual stress which distributed in laser welded joint is primary factor of decreasing fatigue life. Laser Shock Peening (LSP) experiments were conducted on TC4 laser welded joints of 2.5mm thickness, using circular laser spot with pulse duration of 10ns, laser power density of 7.2GW/cm 2 and overlapping ratio of 37.5%. Surface residual stress distribution were studied under LSP of one layer, three layers and five layers. Surface tensile residual stresses converted to compressive residual stresses on LSP area, and compressive residual stresses along longitudinal direction were greater than along transverse direction. The amplitude of compressive residual stress were greatly relative to number of LSP layer. Fatigue life of specimens treated by three layers increased 50% in comparison to untreated specimens (maximum stress:750MPa, stress ratio:0.06). In a word, LSP could adjust residual stress field of laser welded joint, and it is an alternative technology to be potential to substantially improve fatigue performance.