EFFECTS OF RESIDUAL-STRESS ON FATIGUE-STRENGTH OF SMALL-DIAMETER WELDED PIPE JOINT

Bending fatigue tests were conducted to investigate the fatigue streng th of small-diameter socket welded pipe joints. In most cases of large -diameter socket joints, a fatigue crack started from the root of the fillet weld, though the stress amplitude at the root was smaller than that at the toe of the fillet weld. Additionally, the fatigue strength was affected by the weld bead sequence, The residual stress was consi dered to be one of the important parameters governing fatigue strength ; therefore, its effects were investigated. In several types of pipe j oints, the local stress and residual stress distributions were calcula ted by finite element analysis. The residual stresses were compressive at the toe and tensile at the root of the socket welded joints, Based on these results, the effects of residual stresses on the fatigue str ength are discussed for small-diameter welded pipe joints in the prese nt work.