An experimental study was performed to investigate the effect of residual stress on fatigue crack propagation of welded specimen. The specimen made of SM 50A steel was welded by MAG. The shape of the specimen used was CCT for the study of the residual tensile stress while SEN specimen was used for the residual compressive stress.
Results showed that the fatigue crack propagation rate as a function of the effective stress intensity factor in the welded specimen is the same as that in the base metal free of residual stress if we use the effective stress intensity factor, Keff. Therefore it is concluded here that the fatigue crack propagation in welded material is affected by the crack closure phenomenon. It was also found that the residual compressive stress affected the propagation rate more significantly then the residual tensile stress, hence the effect of residual stress is not identical to that of the mean stress.
