Fatigue property analysis of 5083-O aluminum alloy joints considering multiple repaired welded residual stress

Multiple repair welds significantly affect the microstructure and mechanical properties of aluminum alloy joints. In the study, 0 to 3 repair welds were conducted on 5083-O aluminum alloy using melt inert-gas (MIG) welding. Through metallographic observation, hardness testing, and fatigue analysis, a systematic comparison and analysis of the changes in the microstructure and mechanical properties of the repaired welded joints were carried out. Finite element analysis (FEA), validated by the blind-hole method, was used to analyze the residual stress redistribution. The results show that repair welding aggravates grain boundary liquefaction in the partial melting zone (PMZ) and grain coarsening in the heat-affected zone (HAZ), causing a slight decrease in hardness from 87 MPa in the as-welded state to 81 MPa after three repairs. Additionally, the peak residual stress increases notably with the number of repair welds, reducing the fatigue life. Compared with the as-welded joints, the fatigue life of joints after one, two, and three repairs decreased by 11.5 %, 41.2 %, and 35.4 %, respectively. Finally, the study developed the master S-N curve, considering the influence of residual stress and angular misalignment, and provided a theoretical framework for the fatigue life assessment for repaired welded aluminum alloy structures.