Abstract
The fatigue strength of non-load carrying cruciform welded joints were investigated on small welded specimens by the testing method keeping the maximum stress to be the yielding strength of base metal. This stress pattern modifies the existence of welding tensile residual stress in real welded structures. Some fatigue tests were performed at R=0. Slit welded specimens of 250 mm width were prepared to realize the residual stress existed in real welded structures. The tensile residual stress at slit welded part reached to the yield strength. The tensile residual stress on small welded specimens was smaller than the yield strength. The fatigue strength of small welded specimens at R=0 was larger than that of slit welded specimen near fatigue limit region. The fatigue strength of small welded specimens by σ max=σ y tests coincided well with that of slit welded specimen. The knee point appeared around 2x107 cycles for slit welded specimens (R=0) and small welded specimens (σmax=σy). It is pointed out that the design S-N curves in JSSC have same concept with this paper.
