Effect of rotational speed on various performance measures in friction stir lap weld of aluminium alloy 6061 using numerical simulation approach

The quality of a friction stir weld is significantly influenced by the choice of appropriate weld parameters, with rotational speed being one of the key factors. This study aims to examine these elements' influence on physical characteristics of velocity, viscosity, and torque. The performance measures being evaluated include the assessment of maximum weld interface velocity, minimum weld interface viscosity and tool-workpiece interface torque. This study utilises a computational fluid dynamics model to examine the influence of various rotational speeds on the aforementioned performance indicators. The workpiece selected for this study is an Aluminium Alloy 6061, while the tool employed is a truncated conical pin tool featuring a conical shoulder in a lap joint configuration. The study reveals that with an increase in rotational speed from 500 to 2900RPM, maximum weld interface velocity exhibits an increase with decreasing slope. As the rotational speed increases, the minimum weld interface viscosity decreases with decreasing slope. It is also found that tool-workpiece interface torque decreases with approximately constant slope with increasing rotational speed (500 to 2900RPM), meaning a linear decreasing trend. The findings of this investigation are validated through a comparative analysis with previously published data. With this information and the resulting conclusions, friction stir welders can deepen their understanding of how rotational speed affects welding quality.