This study examined low cycle fatigue behavior of cruciform welded joints containing incomplete penetration. Six types of specimens with different sizes of weld penetrations and weld leg lengths were tested under cyclic plastic strains. The test results revealed that the fatigue strength and cracking patterns depend on the ratio of the weld penetration to the main plate thickness and the ratio of the weld leg length to the main plate thickness, respectively. Then, elasto-plastic finite element analyses including the effective notch concept were performed. The results indicate that the fatigue strength and cracking pattern of the specimens can be correlated with the local strain distribution around the effective notch.
