### Tech Briefs

Thermo-mechanical Modeling of Friction Welding

In friction welding heat is generated through mechanical friction between a moving workpiece and a stationary component, with the addition of a lateral force to plastically displace and fuse the materials. During the process no melting occurs. The main benefit of this technique is that it allows materials with very different physical and mechanical properties to be joined. The technique has many applications in the aerospace, nuclear and oil industries [1].

In this News, we present the numerical simulation of friction welding between aluminum and corundum ceramic (Al2O3) rods [2]. A schematic of the physical problem is depicted in Figure 1.

Figure 1 Schematic of the physical problem

The two rods are modeled as axisymmetric solids. The model is subjected to a time varying angular velocity and axial pressure. The ceramic is considered an elastic material and the aluminum a thermo-elasto-plastic material with temperature-dependent work hardening.

The animations above show the evolution of the temperature field, contact tractions and deformations of the rods during the welding process. The nonuniformity of the contact tractions and temperature distribution at the interface during the welding process are noteworthy. Figure 2 shows the nonuniformity of the heat flux at the interface as a function of the radial coordinate at one point in time during welding.

Figure 2 Distribution of heat flux at the interface

In this type of welding, the heat flux generated at the interface of the two materials is a function of the normal pressure between the two parts, coefficient of friction and angular velocity of the welding tool. In other words, the heat flux at the interface is a function of the mechanical deformation at the interface. Also, the coefficient of friction is a function of temperature (Figure 3). As such, the mechanical deformations and heat transfer are fully coupled.

Figure 3 Variation of the coefficient of friction at the interface with temperature

In this study, the full coupling between the temperature and deformation fields is taken into account using the staggered solution scheme available in ADINA; for details see ref. [2]. Figure 4 shows the deformation profile of the aluminum rod obtained using the numerical analysis (left) and physical experiment (right). Excellent correspondence is seen.

Figure 4 Deformation profile of the aluminum rod

This problem solution demonstrates some of the many powerful capabilities available in ADINA to solve problems involving full coupling between mechanical deformations and temperature fields. For more information on the modeling of such problems, see Thermo-mechanical Coupling Capabilities.

References

1. Wikipedia article on Friction Welding