Fatigue analysis of TIG welded joints of dissimilar aluminum alloys

Constant amplitude fatigue testing on 5,083 and 6,061 dissimilar aluminum alloy tungsten inert gas (TIG) welded lap joints was carried out using an MTS material testing machine, and the typical fatigue fractures of specimens were observed, followed by the life prediction. The results of the fatigue tests showed that the specimens shared different fracture forms at high and low stress levels, in addition to the presence of one specimen that fractured at the weld root. Observation on the fractured specimens at the weld root by scanning electron microscope revealed that there were unfused and porosity defects inside the weld, and the stress concentration at the weld root was high, which led to the cracks to sprout here. Combined with the results of finite element stress analyses, the fatigue lives of welded joints were predicted using the notch stress method and the equivalent structural stress method, respectively. The prediction results showed that both methods are effective in predicting the fatigue life, the prediction results errors are within three factors, and the prediction results are all conservative.