Effects of weld geometry and HAZ property on low-cycle fatigue behavior of welded joint

A previous experimental study by the authors clearly indicated that, due to the delay of the crack initiation, the butt-welded joint with smoother weld toe profile and harder weld metal had a longer low-cycle fatigue life. In the present study, supplementary numerical studies considering weld geometries and inhomogeneous mechanical properties are executed. Monotonic tensile and strain-controlled low-cycle fatigue tests on the reheated round bars are firstly conducted to characterize the mechanical properties for different zones of the butt-welded joints. The test results are used to calibrate the material constitutive model, which is then embedded into three-dimensional finite element models to investigate the low-cycle fatigue behavior of the butt-welded joints. The numerical results suggest the necessity of considering the effects of inhomogeneous material properties when evaluating the low-cycle fatigue of welded joints. It is also confirmed that decreasing weld toe stress concentration and simultaneously increasing weld metal strength can maximally increase the low-cycle fatigue life of welded joints compared to the individual changes for either one. These findings are expected to provide some insights into the low-cycle fatigue life improvement of welded joints.