Flow, process forces and strains during Friction Stir Welding: A comprehensive First principle approach

Abstract

Friction stir welding is recent yet spectacular process, which assumes accrescent expanse to evolve as a multi-purpose process. Its potential is greatly being tapped through large-scale experimental and computer simulation-based investigations. Several simulation and empirical models have been proposed but exact fundamental analyses on forces, material flow and strain are still absent. Complexities associated with the process are perhaps the main reason that a fundamental analysis is difficult. A comprehensive analysis of this kind is critical for understanding the evolution of microstructure, mechanical properties of joint and defect formation. This study presents an analysis of material flow, process forces and strains using first principle approach. Results have been presented as exact mathematical expressions in terms of material properties and process parameters. It was demonstrated that the material during stirring experiences direct and shear strains both when it moves from advancing side to retreating side in front of the tool and after rotation deposits behind the tool. It was also demonstrated that the strain significantly reduced from advancing to retreating side; for a typical case the shear strain greater than 10,000% prevails in advancing side and the maximum shear strain on retreating side is of the order of 6000%.