Abstract
The fatigue strength of mild and high strength steel plates and their welded joints is studied with respect to stress concentration factor (Kt) and welding residual stress. The fatigue strength of high strength steel is higher than that of mild steel when Kt is less than 3, though the effect of strength on fatigue strength becomes smaller as Kt increases. The fatigue strength of welded joint of high strength steel, however, is similar to that of mild steel in the case that K2 is 1.68. The tensile residual stress in the welded joints of high strength steels is higher than that of mild steel. The effect of stress concentration factor on fatigue strength and the existence of higher welding residual stress in the higher strength steel welded joint conclude that the welding residual stress has a predominant effect on the fatigue strength of the welded joint of high strength steel.
