铝合金等离子弧立焊穿孔熔池的计算机模拟

Simulation of molten pool for vertical keyhole plasma arc welding in aluminium alloy

根据流体力学理论和传热学机理 ,建立了运动等离子弧作用下立焊穿孔焊接熔池流场和温度场的三维瞬态数值分析模型 ,并采用有限元法对模型进行离散化处理。模型中 ,考虑了熔池内部液态金属的对流传热和熔池外部的固体导热、材料热物理性能参数随温度的变化、焊件表面通过对流和辐射向周围环境的散热以及熔化 /凝固相变潜热对熔池流场与温度场的影响 ,焊接热源采用高斯分布函数 ,计算中对边界条件进行了处理 ,根据穿孔熔池温度场与流场模型的特点 ,采用非均匀网格对单元进行划分 ,并采用分区异步长算法确定时间步长 ,利用ANSYS(一种有限元计算软件 )有限元软件对所建立的模型进行了求解。通过试验测量焊缝几何尺寸与计算结果相比较 ,验证了本模型的计算结果和实际相差不大 ,是基本正确和可靠的。

Based on theories of hydromechanics and heat transfer, a three dimensional transient numerical model of flow and temperature field of the keyhole plasma arc welding ( PAW) molten pool with a moving arc is established, and the model is discretized with the finite element method. In the model, the following factors, which consist of both convection heat transfer of the melted metal inside the pool and heat conduction of solid metal outside the pool, the variation of thermophysical parameters of material with temperature, the effect of the loss of heat, including convection and radiation, and latent heat of phase transformation on the temperature field are considered. Welding heat source is presumed to be Gaussian distribution. Also, the boundary conditions are dealt in the calculation. On the basis of the model, elements are divided according to a non-uniform grid and time steps are defined to a non-uniform step in different subareas. ANSYS, calculating software of finite element technology, is adopted. The results show that the calculated results approximately agree with the experimentally measured geometric sizes and shape of the fusion boundaries, and that the model is basically correct and credible.