The Effect of Welding Tensile Residual Stresses on Fatigue Crack Propagation in Low Propagation Rate Region(Mechanics, Strength & Structural Design)

The effect of welding tensile residual stresses on fatigue crack propagation in low propagation rate(low ΔK) region was studied by experiments. The used material was high tensile strength steel (HT80) of 800MPa class in tensile strength. Center Cracked Tension (CCT) specimens were employed for experiments, and consisted of three kinds ; specimens of base metal only, specimens with longitudinal welded joint (as weld), specimens with longitudinal welded joint (stress relieved). The major results obtained are summarized as follows: (1) Tensile residual stresses lower the threshold value of ΔK. (2) When tensile residual stresses were high, the threshold value of ΔK becomes the lower limit and is independent of stress ratio. (3) The effect of residual stress can be treated as effect of mean stress.