【摘要】 针对基于冷金属过渡(CMT)技术的镁合金摆动电弧增材制造(WAAM)过程，采用流体体积(VOF)法和动网格(DM)技术建立了分别考虑熔滴和熔池受力情况的三维瞬态数值模型，研究了熔滴过渡和熔池流动过程中的温度场和速度场变化.结果表明，相应试验结果验证了所建立数值模型的有效性，熔池和熔滴尺寸参数模拟的误差均在10%之内.在CMT-WAAM开始阶段，基板表面和焊丝在电弧热作用下熔化分别形成熔池和熔滴．在焊丝向熔池送进过程中，熔滴不断长大，并在表面张力作用下长成球形．熔滴金属的热量主要通过热传导的形式向熔池传递，熔池最高温度随着熔滴金属的过渡而升高，熔池最高温度可达2 100.0 K；随着焊丝的回抽，熔池最高温度降低至1 763.6 K．随着焊丝向熔池送进，熔滴的最大速度从1.87 m/s逐渐减小到1.07 m/s，而熔池的最大速度仅为0.87 m/s．当熔滴金属前端与熔池发生接触后，液态金属的最大速度可达到4.21 m/s；随着焊丝的机械回抽，液态金属的最大速度在1.69～4.90 m/s范围内波动．当熔滴与熔池接触发生短路时，熔滴金属从熔池表面流向熔池底部和熔池两侧，增强了对熔池底部和熔池两侧的搅拌作用，使得熔池体积增加；当熔滴从焊丝端部脱离后，熔池中液态金属从熔池底部流向熔池表面和熔池两侧，熔池温度和流体速度随之降低，从而减缓了熔池体积的增加．此外，熔池自由表面在摆动电弧作用下呈现波浪式变形.更多还原

【Abstract】 In the weaving wire arc additive manufacturing(WAAM)of magnesium alloy,enhanced by the cold metal transfer(CMT)technique,a three-dimensional transient numerical model is employed to investigate the temperature and velocity fields during the process. Utilizing the volume of fluid(VOF)method and dynamic mesh(DM)technique,this model accounts for the forces exerted on the droplet and molten pool. The model’s accuracy is demonstrated through experimental validation,with the simulation parameters related to the molten pool and droplet size showing a margin of error under 10%. In the beginning of CMT-WAAM,the molten pool forms on the substrate and the droplet forms at the wire tip owing to arc heat. As the wire feeds into the molten pool,the droplet expands into a spherical shape driven by surface tension. Heat transfer occurs mainly through thermal conduction,causing the peak temperature of the molten pool to rise to 2 100.0 K with the droplet transfer,then drop to 1 763.6 K as the wire retracts. The maximum velocity of the droplet decreases from 1.87 m/s to 1.07 m/s during its incorporation into the molten pool,while the molten pool maintains a maximum velocity of 0.87 m/s. When the droplet meets the molten pool,the maximum velocity of the liquid metal reaches 4.21 m/s. As the wire is withdrawn,this velocity fluctuates between 1.69 m/s and 4.90 m/s. During a short circuit,the metal from the droplet flows from the surface of the molten pool to its bottom and sides,enhancing the stirring effect and increasing the volume of the molten pool. Once the droplet detaches from the wire,the liquid metal moves from the bottom back to the surface and sides of the molten pool,leading to a decrease in temperature and fluid velocity,which moderates the volume of the molten pool. In addition,the free surface of the molten pool exhibits wavy deformation influenced by the weaving arc.更多还原