Research On Numerical Simulation And Nugget Performance Of RSW For Aluminum Alloy

RSW(Resistance Spot Welding) is widely used in areas of aerospace, energy source, electronics, vehicle and light industry, and plays the important role in modern manufacturing industry. However, the nugget formation of RSW is extremely complex and non-linear multi-physics coupling fields, and weld time is transitory and nugget formation is invisible, so that it is difficult for us to observe and research through traditional experiment.This paper makes use of numerical simulation method to search the nugget formation on RSW, and an axisymmetrically electro-thermo-mechanical model is built to simulate variety of the temperature field of nugget during welding, show the course of nugget generated, formed and grown. Finally nugget formation on RSW is completely analyzed.From the process of how to design nugget of RSW, a reverse method, based on shearing performance of nugget, is put forward. The model about nugget dimension and shape is set up through mechanical performance of welding structure, so that eligible nugget able to meet shearing performance is obtained. According to eligible nugget, welding parameters are ascertained through simulating temperature fields. It will be used for directing welding process parameters at present.At the aspect of residual stress, temperature grads is high, nugget expanse and shrinkage is big, and pressure is function during spot welding, so the elastic and plastic distortion is severe, and nugget of RSW has a big residual stress. Residual stress can have influence in reliability and fatigue life of nugget design. As a result, residual stress of welding spot is analyzed in electrode pressure force and in heat load respectively. At the same time, residual stress in different welding force and welding time is checked by X-ray diffraction. Testing and computing results show average residual stress through numerical simulation has an almost common with that of X-ray diffraction. It shows correct through numerical simulation.At fatigue of welding spot, two researches are done. For one thing, the stress and strain response is calculated according to the loads and geometric structure, which is a premise of fatigue analysis. For another, the polar plot of fatigue damnification along nugget is depicted considering about stress and strain response and material performance parameter. The mechanism of fatigue damnification on spot welding is accurately realized and known, and it will make for design of fatigue life. Finally, fatigue life from influence on residual stress is discussed in quality.