Influence of varying shoulder profiles in pin-less tool on friction stir welding of thin plates

This study explores the thermal and mechanical characteristics of Friction Stir Welding (FSW) using pin-less tools with varied shoulder geometries to weld 2 mm dissimilar plates. FSW is a solid-state joining technique known for minimizing weld defects and enhancing joint integrity, particularly in the applications requiring high precision and low thermal distortion. Using simulation-based analysis via ANSYS, three custom-designed tool profiles are considered (i.e) spiral, concentric, and diamond tip, were evaluated. The rotational speeds considered are 500, 1000, and 3000 rpm at a constant traverse speed of 90 mm/min. The 3D models of the FSW tool with required shoulder profiles and thin plates are developed using Solid works. The tool and plates are characterized using tungsten carbide and aluminium-magnesium for workpieces. The simulations focused on key field variables including, temperature distribution, residual stress, and deformation on the welded plates. Results indicated that the spiral tool produced highest temperatures and residual stresses, due to its aggressive stirring action and posed risks of distortion. The concentric tool demonstrated a more balanced thermal profile with moderate stresses and deformations. However, the diamond tip tool emerged as optimal, generating the lowest peak temperatures and residual stresses, while maintaining minimal deformation. Its sharp geometry localized the heat generation, promoting controlled plastic flow and structural stability. The study concludes that the diamond tip tool at medium rpm (around 1000 rpm) achieves the most efficient compromise between thermal input and mechanical performance. This configuration offers enhanced dimensional precision and mechanical integrity, especially relevant to microelectronics, automobiles, aerospace, and medical device manufacturing. The findings support further development of customized FSW tooling for high-performance, precision-critical applications.