Influence of Welding Residual Stresses on Fatigue Crack Initiation Life

Fatigue tests were conducted on mild steel (SS41) plate in which residual stresses were varied by different heat treatments: as-welded, and stress relieved at 380, 500 and 620 deg C. Total fatigue life was divided into initiation life and propagation life. The influence of welding tensile residual stresses on crack initiation life was studied experimentally. Crack initiation life increases as welding tensile residual stress becomes lower. The influence of welding tensile residual stress on crack propagation life is smaller than that of crack initiation life. Scatter of failure life is caused by crack initiation life; scatter of crack propagation life is small. This phenomenon is not affected by welding residual stress.--J.H.B.