Temperature distribution and residual stress in Friction Stir Welding process

Abstract

Friction Stir Welding is an advanced solid state joining process invented as an alternative to join materials which are unfavourable to join using fusion welding technique. In Friction Stir Welding, the non-consumable tool is rotated and is slowly dived into the centreline and simultaneously progressed along that line. The heat generation in the process is a combined effect of frictional heating and heat because of the plasticization of the material. In this paper, the Finite Element package COMSOL Multiphysics 5.2a is used to develop a three dimensional numerical model to generate thermal profiles during welding, which is validated through experimentation. Due to the differential heating and cooling and the plasticization of the material, residual stresses develop in the material. The nature of the residual stresses significantly affects the quality of the joints. To analyse the residual stresses developed, three different approaches; namely experimental, analytical and numerical methods are used. Experimentally, residual stress is obtained by X-Ray Diffraction technique, Masubuchi and Martin’s longitudinal stress equation is used for analytical measurements and also residual stress is obtained numerically. The three approaches used for measurement of residual stresses are in well agreement with each other.