Numerical modeling of friction stir welding

Welding is a joining process commonly used in industrial environments, based on techniques such as plasma, laser, electron beam or resistance welding. As with the more conventional friction welding methods used since the early 50s, friction stir welding is carried out in the solid phase, without the addition of material. This recent process, also known as Friction Stir Welding (FSW), was developed at TWI (The Welding Institute) in the early 90s. The first applications of this process focused on aluminum alloys, particularly those considered "difficult to weld". Experience has shown that welding without melting enables the friction stir welding process to join this type of material. In addition, phenomena such as hot cracking or loss of volatile solutes can be avoided. Numerous developments are currently underway to extend the scope of the FSW process to other materials such as steels and titanium alloys. There is also a variant of the FSW process known as Friction Stir Processing (FSP), the aim of which is to modify the local characteristics of a component by stirring, without seeking to weld.

The FSW process can be used to join different materials, such as steel with an aluminum alloy. This type of welded joint exists in many industrial sectors, such as the automotive industry, where fusion welding is simply not appropriate, given the significant variation in thermo-physical properties: mechanical behavior, thermal diffusivity or chemical composition that can lead to the formation of intermetallics detrimental to weld quality. These and other factors contribute to the asymmetry of thermal fields, making fusion processes difficult to apply. It is for this reason that the application of friction stir welding to welds of different alloys is of great technical and economic interest. Indeed, the FSW process applied to combinations of relatively soft alloys (e.g. Al/Mg) is of particular interest in the aerospace and automotive industries, as in many cases there are no other alternatives. Despite this, the FSW process induces microstructural changes, residual stresses and distortions that are difficult to control. All these phenomena can affect assembly efficiency, both in terms of final geometry and fatigue strength.

In an increasingly competitive industrial context, companies are obliged to develop their products to ever tighter deadlines and at ever lower costs. Controlling manufacturing processes and the consequences they have on the products produced is an essential success factor. In this context, characterization and numerical modeling of the FSW process are of particular interest when it comes to studying feasibility, optimizing operating parameters or analyzing the service life of an assembly. The aim of this article is to review the numerical modeling methods...