Residual stress state behaviour under fatigue loading in pipeline welded joints

Compressive residual stress state behaviour under fatigue of the welded joi nts of a pipeline were investigated. The regions on the intersection betwee n the welded joints of the longitudinal pipe manufacturing seam and the cir cumferential welded joints of the pipeline construction were investigated. Stress-controlled fatigue loading was carried out at various stress ratios of the yield strength of the base metal. Surface residual stresses were int roduced in samples by shot-peening treatment and were measured using X-ray diffraction techniques. The results showed that compressive residual stress es which, unless they are relieved or inverted during the process of fatigu e loading, make crack initiation difficult.