Investigation on Fatigue Strength of Aluminum Alloy 6061-T6 Resistance Spot Welded Going under Tensile-Shear test

Resistance spot welding(RSW) is one of the most popular welding methods in joining sheet metals of cars, and etc. In RSW process, a high electric current is passed throw two sheets via electrodes, which results in the generation of a melting zone between the sheets, called nugget. The main purpose of this study is experimental investigation on static and fatigue strength of aluminum alloy 6061-T6 with 2 mm thickness. To achieve this goal, many samples were prepared and welded by different RSW’s parameters. The mechanical strength of welded samples was examined under tensile-shear test. The results show that, by increasing the nugget size, the static strength is improved. In addition, however at first, the fatigue strength is increased by improving the nugget size; it’s decreased significantly after a certain nugget diameter. The micro-structural study indicates the formation of cracks in the HAZ after the certain nugget diameter. However, these liquation cracks have no effect on the static strength of spot welded samples; they cause dramatically changes in the fatigue strength of samples.