Ultrasonic Welding Essay

Ultrasonic metal welding is a promising welding method for joining of metals and their alloys. During the welding process, the ultrasonic vibration energy is committed to the welding interface in which temperature rise， serve plastic deformation and metallurgical reaction are produced. Comparing with fusion welding, the USMW is a solid welding technology that has the advantages of a shorter process and no other material consumed. For other processes, it is difficult to obtain a high quality of Cu/Al joint by resistance spot welding due to conductive properties of the materials. Comparing with friction stir welding, ultrasonic softening reduces the force required to produce serve plastic deformation. This makes the tool not easy to be broken.

[3] concluded that interface friction resulted in tremendous plastic deformation, which was beneficial for joint formation. Ni and Ye [4] found that very fine grain (～4.2 μm) distribution at the weld interface. However, the mechanism of ultrasonic welding is not clear due to the weld process was complicated dynamic process, and the influence of ultrasonic soften of materials on temperature rise and materials plastic deformation are not comprehensively understood by experiments study alone. Finite element method (FEM) can be used in simulate the physic phenomenon in the dynamic process, and was widely used in recent study. In the earlier simulations, the ultrasonic softening of materials is not considered in their models. Siddiq and Ghassemieh [5] developed a UC model, which firstly included thermal softening as well as ultrasonic softening. They found that the thermal were decreased by ultrasonic softening. Elangovan, et al. [6] proposed an axisymmetric model and also included plastic deformation heat. They studied the temperature and stress distribution and found that the peak temperature develops at the center of weld interface. Kim, et al. [7] proposed a 3-D thermo-mechanical analysis of an ultrasonic spot welding