EFFECT OF RESIDUAL TENSILE STRESSES ON THRESHOLD LEVEL FOR FATIGUE CRACK PROPAGATION IN WELDED JOINTS OF SM50B STEEL.

The fatigue crack propagation rate and stress intensity threshold level were measured on welded joints made by manual arc welding with covered electrode, gas metal arc welding, and submerged arc welding. The material was SM50B steel. The fatigue crack propagation properties of the weld metal and the heat-affected zone were similar to each other and inferior to those of the base metal. The stress intensity threshold level of the joints was about one fourth that of the base metal. Removal of tensile residual stresses by postweld heat treatment improved the fatigue crack propagation properties.