Heat Transfer in Friction Stir Welding—Experimental and Numerical Studies

Abstract

In the friction stir welding (FSW) process, heat is generated by friction between the tool and the workpiece. This heat flows into the workpiece as well as the tool. The amount of heat conducted into the workpiece determines the quality of the weld, residual stress and distortion of the workpiece. The amount of the heat that flows to the tool dictates the life of the tool and the capability of the tool for the joining process. In this paper, we formulate the heat transfer of the FSW process into two boundary value problems (BVP)—a steady state BVP for the tool and a transient BVP for the workpiece. To quantify the physical values of the process the temperatures in the workpiece and the tool are measured during FSW. Using the measured transient temperature fields finite element numerical analyses were performed to determine the heat flux generated from the friction to the workpiece and the tool. Detailed temperature distributions in the workpiece and the tool are presented. Discussions relative to the FSW process are then given. In particular, the results show that (1) the majority of the heat generated from the friction, i.e., about 95%, is transferred into the workpiece and only 5% flows into the tool and (2) the fraction of the rate of plastic work dissipated as heat is about 80%.

A Comparison of Different Finite Element Methods in the Thermal Analysis of Friction Stir Welding (FSW)

“…In the model, a transient thermal condition in which the power was recorded experimentally and defined in the model as a constant value was used. Dong et al [84] and Chao et al [85] compared the experimental and the numerical results of the generated heat energy during FSW using the Lagrangian method. In Chao's model, a steady state condition was employed for the tool and a transient condition was used for the plates.…”

“…In some Lagrangian FE models, over-prediction problem solved by experimentally measuring of the power data and defining this data as an input parameter in the model. These models [85][86][87][88][89][90][91] also were used to find the effect of the latent heat in the peak temperature.…”

Simplified Thermo-Mechanical Modeling of Friction Stir Welding with a Sequential FE Method

“…A substantial effort is usually needed to determine how much heat flows into the tool and how much to the plates. This is highly dependent on the changing friction coefficient, downward force, temperature and the tribology conditions of the contacting surfaces [12]. For simplified models, it is essential to know this and to apply the corresponding heat input to the FE model.…”

“…4 Convection boundary conditions with film coefficient h1 are specified for workpiece surfaces which are exposed to the air. The radiation heat transfer of the surfaces is lumped into the convection, as it is reportedly small [12]. The conduction heat exchange between the bottom surface of the workpiece and the backing plate is simplified by using a larger convective coefficient.…”

Retardation of fatigue crack growth in aircraft aluminium alloys via laser heating – Numerical prediction of fatigue crack growth

“…However, in [28][29][30], for example, friction stir welding of aerospace aluminium alloys was investigated. In [26,[31][32][33][34][35][36], the resulting distortions and residual stresses after laser beam welding of aluminium T-joints were predicted.…”