TA31钛合金电弧增材制造过程液桥过渡数值分析

Numerical Analysis of Liquid Bridge Transfer in Wire Arc Additive Manufacture Process of TA31 Titanium Alloy

建立了电弧熔丝增材制备TA31钛合金过程传热传质的三维瞬态计算流体力学模型,采用流体体积法对自由表面进行追踪,计算了熔滴生长、液桥过渡和脱离焊丝进入熔池的动态演化,以及在表面张力、电弧压力、电弧剪切力、电磁力、重力和热浮力的作用下熔池流体流动的速度分布,并通过与高速成像以及沉积层横截面的比较,验证了该数值模型的有效性。结果表明:液桥过渡模式对熔池冲击较小,有利于减少成形表面的不规则性。随着熔池几何形状的扩大,沉积层高度先增大后减小,最后趋于稳定。在电弧压力和表面张力的作用下,熔池表面形成凹陷,熔池内部产生对流。惯性力和表面张力是影响液桥流动的最重要驱动力,粘性力和重力的影响可以忽略不计。

The three-dimensional transient computational fluid dynamics model of heat and mass transfer in the wire arc additive manufacturing(WAAM)process of TA31 titanium alloy was established.Through the volume of fluid method,the free surface was tracked.The dynamic evolution of droplet growth,liquid bridge transfer,and detachment from the wire tip into the molten pool was calculated.The velocity field of the molten pool driven by surface tension,arc pressure,arc shear,electromagnetic force,gravity,and buoyancy was calculated.The validity of the numerical model was confirmed through the results of high-speed imaging and the crosssections of weld bead.Results show that the liquid bridge transfer mode exerts less effect on the molten pool,which is conducive to reduce the irregularity of the bead surface.With expanding the molten pool,the height of weld bead is firstly increased,then decreased,and finally becomes stable.Under the influence of arc pressure and surface tension,a crater forms on the molten pool surface,and the convection occurs inside the molten pool.The inertial force and surface tension are the most important dynamic forces in the liquid bridge transfer process,and the influence of viscosity and gravity can be neglected.