Numerical Simulation Of Spot Welding For Aluminum Alloy

Aluminum alloy has been widely used in aerospace,automobile manufacturing and other areas by its small proportion, good corrosion resistance, easy to process and so on. Resistance spot welding is one of the main connection technology for aluminum alloy thin sheet. The spot welding performance of aluminum alloy is poor because of its high thermal conductivity and low resistivity characteristics. The process mechanism of aluminum alloy RSW is the base and key to solve the problem of spot welding.The paper firstly simulate the spot welding process of LF2 aluminum alloy with 2mm thickness,and then create thermal ,electrical and mechanical coupled analysis model through the finite element analysis software ANSYS. Using numerical simulation method, the mechanism and influence factors of aluminum alloy spot welding is investigated. The influence analysis of the temperature field and stress field under different welding process parameters lays the foundation to realize the real-time monitoring and process parameter optimization of aluminum alloy spot welding process.The contact behaviors and features of welded stress and strain with taper-shaped and dome-shaped eletrodes under the conditions of aluminum resistance spot welding preloading phase are compared,and the use of dome-shaped electrode is advantageous to limit early splash and improve surface quality of weldment.According to dome-shaped electrode contact analyzing result,the ohmic heating and cooling phase of aluminum spot welding are simulated. In the ohmic heating moment,the temperature of joint surface rises at first,and finally formed ellipse nugget within the workpiece. The compressed stress in nugget is main,and the stress value of nugget center is quite small at the end of heating phase. In the cooling phase ,the nugget instantly change to solid state, the isotherm remains the ellipse contraction,and the temperature gradient gradually flatten. The stress of welding area transforms gradually to tension stress,ultimately, the residual stress of welding area is bidirectional tensile stress ,and there is larger stress concentrating in the joint surface at the edge of strenth area.Using the same simulation, the influence rule of welding process parameters change to the spot welding temperature field and the residual stress is analyzed,and for improving simulation accuracy, the contact radius of the model is modified according to the change in the spot welding parameters. The analysis result indicate: with the increasing of welding current, nugget diameter and penetration rates increase, the residual stress of welding area will be reduced accordingly;The impact on nugget size of circular time is similar to welding current but weaker effect,and after increasing a certain stage, the residual stress of the welding area is no longer affected; With the electrode pressure increasing, nugget diameter Change little, while penetration rate decrease significantly, the residual stress distribution of joint surface is more sensitive to the change of electrode pressure.Do spot welding experiments to aluminum alloy plate in the same condition of simulation, prepare low magnification metallographic photos of joint ,and measure nugget diameter and penetration rate. Experimental results and simulations are in good agreement, which verify the simulation method is reasonable and the simulation results is accurate .