Research On Welding Deformation Prediction And Control Of Car Beam

More and more large welding structures are used in industries with the development of economy. However the welding deformation is inevitable in the welding structure manufacture process. The welding deformation not only influences the structure size, damaging the assembly accuracy, but also reduces the load capacity of structure. So has great significance to predict and control of the welding deformation of large structure.This paper adopts the "local-global" method to predict the welding deformation of car beam. SYSWELD software is used to calculate the local model, while Pam-assembly software is used to predict the global model’s deformation. The mix application of 3D and 2D unit in the calculation ensures the balance of simulation accuracy and efficiency. The results show that the "local-global" method can exactly predict the welding deformation, meanwhile different welding sequence on welding deformation are analyzed. It is concluded that symmetry welding sequence from the middle to the bilateral is the optimum welding sequence, which provides reference date for automatic production.Welding with trailing cooling which considers the endothermic Gauss heat source mode as cooling model is applied to control welding deformation in this paper. Both experimental and numerical methods are employed to study the control of welding deformation mechanism. Compared to conventional welding, welding with trailing cooling generates noticeable low temperature field in the cold source parts due to the effect of rapid cooling rate, leading to obvious "saddle" temperature field. Quenching of high temperature metal produces tensile effects on surrounding metal and plastic strain and residual stress are reduced, flexural deformation is decreased from 3.8 mm to 1.0 mm, reducing by 74%. The effects of cooling distance and cooling power on welding deformation were studied. The results show that with the distance decreasing, the temperature field distortion increases and longitudinal residual stress decreases, and the effects of controlling welding deformation become more obvious. But the distance cannot be too small because of the actual engineering situation, and the "isothermal method" is applied to select a suitable space scope. With cooling power increasing, the minimum temperature and longitudinal residual stress become smaller, and the control of welding deformation becomes more effective. Both indicate that the welding deformation initially decreases then remains unchanged with the growth of water flow.Welding with trailing cooling is applied on car beam’s welding. "Isothermal method" is used to determine the cooling distance, and "ratio method" is used to select suitable cooling power. Effects of trailing cooling on beam’s welding deformation were simulated. Results show that the welding with trailing cooling can obviously control welding deformation, which founds the theoretical basis for the practical application of welding with trailing.