Thermomechanical modelling friction stir welding aluminium 2024-T3

Abstract

This paper investigates a metal joining process called Friction Stir Welding (FSW). FSW is an innovative welding technique invented by TWI Ltd. in Great Britain in 1991. Applications of FSW can be found in the shipbuilding, aerospace and automotive industries. In the recent past some research projects have been carried out on the numerical simulation of FSW and yet problems in modelling the process still exist. The aim of the research project is the development of a numerical model to provide a better understanding of the FSW process. The commercial code DEFORM 2D was used to simulate the material flow pattern and the initial plunge force during the FSW of Aluminium 1100-O assuming the material to deform plastically. Also, a thermomechanically coupled, rigid-viscoplastic DEFORM 3D analysis was performed to predict the forces, stresses, strains, strain rates and temperatures occurring during the FSW of 4.89 mm thick sheets of Aluminium 2024-T3 (Alclad). The experimental welding tests were performed on a vertical milling machine adapted to run the process and appropriate tooling was designed. The experimental and FE results were then analysed and compared. The main findings of the work suggested that the DEFORM package was able to effectively model the large deformations encountered during the FSW process but did not have the capability to generate the expected high temperatures at the end of the plunging process. As a consequence approximate initial temperatures boundary conditions were used in the simulations.