Digital simulation of the friction stir welding process

Abstract

A recently developed welding process has proven to be well suited to making high strength aluminium alloy joints. This friction stir welding (FSW) process was invented and patented by The Welding Institute (TWI). The objective was to develop a means of simulating the process that could subsequently be used as a means of enhancing the design of these welded structures. Furthermore, these methods will enable easier development of the process, and for improved knowledge of the quality of the workpieces, in particular in terms of residual stresses. It will also make for better forecasting of the lifetime of these structures. These three-dimensional thermomechanical transient calculations were made using two finite element codes (SYSWELD (ESI Group) and MARC (MSc Group)). The heat input of the process was modelled by two different digital heat sources: a surface source with SYSWELD, and a volume source with MARC. The temperature results obtained are then compared with the experimental thermal measurements taken using thermocouples and an infrared camera. Neither the material flow nor the tool itself were modelled in the mechanical calculation. However, the mechanical characteristics of all the microstructure zones (Fig. 1) were factored into the calculations.