Prediction of weld zone shape with effect of tool pin profile in friction stir welding process

Abstract

This article investigates the effect of tool pin profile on weld zone shape using computational fluid dynamics techniques in friction stir welding process. The effect of tool pin profile on weld zone shape was investigated by four different pin profile tools: Cylindrical, conical, cylindrical-conical and stepped-conical. In the numerical simulation process, workpiece material and tool are considered as non-Newtonian fluids and solid material, respectively. And simulation is carried out under transient state condition. Temperature distribution and material flow profile developed by the tool pin profile are analyzed for the understanding of viscosity profile of the weld zone region. Critical iso-viscosity surface is developed from the viscosity profile to determine the difference between deformed and undeformed material, which is finally used to determine the weld zone shape. The simulation result shows that maximum temperature and material flow velocity are produced by stepped-conical pin profile tool with respect to all other tools. It is observed from the iso-viscosity surface analysis that a vase-shaped geometry developed around the contact region of the tool and workpiece. The weld zone shape produced by stepped-conical pin profile tool is cylinder dominant vase shape, and weld zone shape of all other tools is basin dominant vase shape. Numerical model was also validated with experimental results of temperature distribution and weld zone shape thickness which showed good agreement.