Numerical Simulation Of Resistance Spot Welding Process Of Aluminum Alloy Of Copper With Aluminum

Resistance spot welding (RSW) of aluminum alloys which are widely used in aerospace, electronics, vehicles and light industry and so on, has an important status in the modern manufacturing industry. Because the aluminum alloys resistance spot welding existence of instability in weld quality and electrode with low efficiency in the continuous welding process, it has limited the applications and development of the resistance spot welding in these areas. The alloying between copper electrode tip and aluminum alloy sheet surface during the spot welding is the main reason of decreasing electrode life, which is effected by the higher electrode tip temperature and pressure distribution. The resistance spot process is a highly nonlinear, multi-physical coupling complex process. It is difficult to observe the resistance spot process, due to the weld period temporary and the unobvious molten bath forming process. Therefore, the electrode collapse is researched by means of numerical simulation with ANSYS software. Specific results from the research in this paper are as follows:According to the elastoplastic theory and contact theory,pre-squeeze contact analysis for RSW is developed by means of numerical simulation, and the initialized conducting region is decided by this model. According to the basic equation of depicting RSW process, an axial symmetric finite element model is developed of mechanical,thermal and electrical coupled analysis for the process of aluminum alloy RSW.Temperature field and stress field of RSW are analyzed by numerical simulation with couple model. The results show that contact resistance distribution is not uniform in the initial stage, which cause a high temperature in contact surface of local and even can achieve the temperature of the alloying between copper and aluminum. This kind of phenomenon is changed in a very short time, and most of the energy is engendered on the edge of the electrode tip, where is also the stress concentration.In order to further study the mechanism of the alloying of copper and aluminum, a finite element model based on the diffusion reaction of copper and aluminum was given. According to the similarity of diffusion equation and hears transfer equation, thermal analysis was used to simulate the diffusion process. Temperature was used to represent the concentration. Through the analysis of the diffusion reaction, some about the reliable theory of alloying of copper and aluminum is put forward: under electrode pressure, copper and aluminum form mechanical mixture, and both of them are mixed on atomic scales with the form of atomic diffusion. Finally, Al solubilizes in copper and the solid solution (α) is formed. When the content of copper element in aluminum matrix exceeds 5.65% and reaching the reaction temperature, intermetallic compound of copper and aluminum is generated. In addition, electrode tip is generated plastic deformation under high pressure and temperature, which improves internal dislocation density, and it is beneficial to the spread of aluminum atom.