Fatigue strength assessment of load-carrying cruciform joints with material mismatching in low- and high-cycle fatigue regions based on the effective notch concept

This study examined the applicability of the effective notch concept to the low- and high-cycle fatigue regions for load-carrying cruciform joints. Low- and high-cycle fatigue tests were performed on specimens with various strength matching conditions and incomplete penetration ratio. Fatigue test results revealed that the effect of strength matching becomes obvious in low cycle fatigue region, while, it was negligible in high cycle fatigue region. Different failure patterns can be observed for specimen with different strength mismatching condition in the low cycle fatigue tests. Elasto-plastic finite element analyses were performed under the same conditions as the experiments. The effective notch strains were determined at the crack initiation points. A unique relationship between effective notch strain and fatigue life was obtained regardless of matching condition and incomplete penetration ratio.

► Specimens were made with various strength mismatch and incomplete penetration.
► Low- and high-cycle fatigue tests were performed on specimens.
► Strength mismatch causes different failure patterns in the low cycle fatigue test.
► Elasto-plastic FEM was performed under the same conditions as the experiments.
► A unique relationship between effective notch strain and fatigue life was obtained.