Low- and high-cycle fatigue behavior of load-carrying cruciform joints with incomplete penetration and strength under-match

The fatigue strengths of load-carrying cruciform joints with incomplete penetration and a strength mismatch between the base metal and the deposit metal were studied. Low- and high-cycle fatigue tests were performed on specimens with five matching conditions and two sizes of incomplete penetration. The test results revealed that the failure life was governed by crack propagation in both the low-cycle and high-cycle fatigue regions, and the crack propagation paths differed according to the matching and loading conditions. In addition, the fatigue strengths of the joints were compared for the degree of strength matching and the size of incomplete penetration in the low- and high-cycle fatigue regions. It was found that the effect of strength matching on the fatigue strength is negligible in the high-cycle fatigue region, but it becomes large in the low-cycle fatigue region and significantly reduces the fatigue life of the specimen in the under-matched joints.