Analytical and experimental investigations of optimum thermomechanical conditions to use tools with non-circular pin in friction stir welding

Friction stir welding tools with non-circular pins exhibit comparatively superior weld quality than circular pins. Improper selection of process parameters directs towards excess or insufficient heat supply which deteriorates weld quality and tool life. This necessitates exact prediction of heat generation with respect to the chosen pin geometry that is required to optimise process parameters. In this paper, a novel analytical model is developed to quantify the percentage reduction in heat generation on the replacement of circular tool pin with non-circular. Experiments were conducted using tools with different pin geometries to validate the proposed model. Based on the obtained results, optimum process variable selection charts were prepared with respect to the reduction in heat supply to facilitate amiable environment to use non-circular tool pins. Weld quality on the suggested range in the charts was examined through macro structure, hardness and tensile analysis.