脉冲激光表面熔凝熔池演变数值模拟

Melting and Solidification Simulation of Pulse Laser Molten Surface

为了研究脉冲激光作用过程中表面快速熔化与凝固的过程,建立了脉冲激光作用熔池金属熔凝的二维热流耦合模型.考虑重力、材料物性随温度的变化等的影响,利用焓-多孔度方法和用户自定义函数对表面熔化凝固的固液相界面演化进行了分析;采用熔化/凝固模型对熔池内的瞬态温度场、速度场和流场进行了数值模拟,并以实验验证模拟结果.计算结果表明:表面熔化与凝固的固液相界面的移动呈现不同状态;在熔凝过程中,熔池内除存在一对方向相反的主环流外,还存在多个环流;流体的速度随着温度的降低而减小且速度最大的区域位于熔池表面附近.

To investigate the convection and track liquid-solid phase interface in the rapid melting and solidification of laser melting, two-dimensional thermal-fluid coupled model for the pulse laser processing was built. The gravity force and material property varying were considered in the computation. A liquid-solid phase interface evolution was traced with enthalpy-porosity method and user defined function. The temperature distribution, streamlines and velocity distribution during the process were simulated with melting/ solidification model. The results were validated with experiments. The simulation results show that liquidsolid phase interfaces develop differently in the melting and solidification process. Several circulation flow regions exist besides a pair of main circulation flow in the molten pool. The flow velocity reduces with the decreasing temperature and the maximal velocity locates near the molten pool surface.