Key Technology Research On Welding Numerical Simulation Of Aluminum Alloy Body Of EMU

Based on medium and long-term development plan of China Railway, by2020China’s high-speed mileage will reach16,000km. With the rapid development of high-speed railway, the higher quality of the manufacturing and processing of high-speed trains are required.To achieve lightweight purpose, aluminum is widely applied to the body structure, during the manufacturing process of EMU body, welding is an essential meathod. Due to the internal of workpiece will produce the non-uniform plastic deformation in the welding process, this will make the workpiece generate welding residual stress.Welding residual stress will bring great harm to welded structure, such as reducing the static strength of structure, reducing the fatigue life of the structure and reduce the corrosion resistance of the material. So by means of numerical simulation to simulate the welding process to study the law of welding temperature field and welding residual stress, which can be based on the simulation results to develop optimal welding parameters, it also meets the requirements of railway vehicle high performance and high standard.Firstly, put forward the secondary development method of heat source of SYSWELD and obtain the "double ellipsoid+cylindrical" mixed heat source.Secondly, use the mixed heat source model to simulate the transient evolution of the molten pool during the welding process. By comparing the molten pool result of numerical simulation with the actual cross-sectional shape when reaching quasi-steady state, it shows that the simulation result is consistent with experimental result. Studying the affect of welding parameterson the workpiece temperature field and molten pool shape.Finally, analyze the impact of welding process on welding residual stress of aluminum alloy body of EMU. Analyze the impact of the law on residual stress in different preheating temperature by means of numerical simulation; Analyze the impact of speed on residual stress under the same process parameter. Simulate the welding residual stress of8welds of the side walls and16V6pass K-K side in different welding sequence, the result shows that different welding sequence will have a great impact on the size of the residual stress, we can obtain optimal welding sequence through numerical simulation.