Low-cycle fatigue properties of welded microzones based on the local strain approach

Due to the inaccuracy of the nominal strain approach in evaluating the low-cycle fatigue (LCF) properties of welded joints, a local strain approach considering mechanical heterogeneity of welded joints and based on elastic-plastic finite element analysis was proposed to evaluate the LCF properties of welded joints accurately. The LCF tests of smooth specimens of the welded joint of heat-resistant steel and the weld metal were conducted. The elastic-plastic finite element analysis of the smooth specimens of the welded joints during loading was calculated. The LCF properties of the welded joint were evaluated using the nominal and local strain approach. The results showed that the smooth specimens of the welded joint fractured at the softened weld zone. The LCF properties evaluated by the nominal strain approach were conservative. Since the mechanical heterogeneity of the welded joint was considered by the local strain approach, the LCF properties were evaluated based on the local strain in the fractured microzone. Therefore, the strain−life curve of the welded joint obtained by the local strain approach was close to the strain−life curve of the material of the fractured microzone.