抄録
This paper describes the effect of a small notch at the toe of the reinforcement on the fatigue strength of welded joints. Both large and small notches appeared at the root of the toe. It was clarified from a detailed survey on the toe shape of the joints welded under several conditions that the radius of the large notch was larger than that of the critical radius. The fatigue strength of welded joints was determined by the crack initiating condition when the fatigue strength was evaluated based only on the shape of the large notch at the toe without regard for the effect of the small notch existing at the root of the large notch.
The depth of the small notch was about 35μm, and was less than the length of nonpropagating cracks which was in the range of 40-80μm depending mainly on the hardness of the carbon steel used in this study. This means that the small notch does not give any effect on the fatigue strength of welded joints.
The out of plane bending fatigue tests revealed the validity of the above estimation on the fatigue strength of welded joints. The fatigue strength of welded joints was not affected by the small notch but depended on the shape of large notch at the toe.
