铝合金双脉冲MIG焊过程的温度及应力变形模拟

Simulation of temperature,stress and deformation during double pulsed MIG welding of aluminum alloy

针对6061-T6铝合金薄板T型接头的双脉冲MIG焊,采用弹塑性有限元方法对其温度场与应力-应变场进行模拟,并将热输入简化为以低频脉冲频率在强、弱脉冲之间周期性转换的热源,同时运用生死单元技术模拟焊丝的填充过程。结果表明:焊后T型接头的残余应力主要集中在焊缝处,其最大值为273 MPa,导致受热侧翼板产生了1.61°的角变形。焊接过程中的温度场和应力场均以低频脉冲频率周期性变化,与强脉冲群相比,弱脉冲群阶段的熔池温度较低且体积较小,而熔池及周边金属的受力较大。强、弱脉冲之间的周期性转换引起熔池尺寸及受力的周期性变化,有利于鱼鳞状焊缝和细小均匀的焊缝组织的形成。熔池尺寸、焊接热循环曲线以及T型接头焊接变形的模拟结果与实验结果吻合较好,验证了模拟的可靠性。

Based on thermo-elastic-plastic model, a three-dimensional finite element model was applied to simulating the temperature, residual stress and deformation fields of 6061-T6 T-joint weld during double pulsed MIG （DP-MIG） welding process. During describing the heat source of DP-MIG the heat input was simplified to change between thermal pulse and thermal base at the cycle of low pulse. The technique of element birth and death was employed to simulate the weld filler in T-joint fillet welds. The simulation results show that the stress located at fusion zone reaches 273 MPa, which induces a 1.61° angular distortion. Besides, temperature and stress fields will change with the cycle of low pulse. The temperature of weld pool is lower and the weld pool size is smaller during thermal base compared with that in thermal pulse, while the stress of weld pool shows an opposite tendency. The cyclic change of temperature and stress between thermal pulse and thermal base during welding process results in the formation of typical ripples appearance on the weld joints, as well as enhances the flow of weld pool to produce more uniform and finer microstructure. The comparison between the experiment and simulation results shows a good agreement, which verifies the precision of welding simulation.