激光深熔焊细长小孔数值模拟与试验研究

为了准确模拟焊接过程中小孔的瞬态形成过程,采用水平集法追踪小孔气/液界面,运用混合理论处理固/液相变,建立了气、液、固三相耦合模型。该模型综合考虑了表面张力、浮力、反冲压力、固/液间摩擦力、潜热、对流以及辐射等影响因素,数值计算得到小孔演变的动态过程和孔内外金属蒸汽行为。模拟发现,小孔形貌瞬态变化,前后壁凹凸变形,逐渐趋于稳定,孔径约为1mm;金属蒸汽与小孔相互影响,最大蒸汽速率为5.3m/s。采用改进的"三明治"方法进行激光焊接实验验证,实验结果与模拟结果相吻合。结果表明,水平集法追踪小孔自由界面在激光深熔焊模拟中具有良好的适用性。这为小孔的研究提供了理论依据。

Numerical simulation and experimental research of slender keyholes during deep penetration laser welding

In order to simulate the transient formation of a keyhole during the welding process accurately, the gas-liquid interface of the keyhole was traced by means of the level set method, the solid-liquid phase transition process was disposed by the mixture model, and the gas, liquid and solid coupling model was established. The factors, such as surface tension, buoyancy, recoil pressure, friction between solid and liquid, latent heat, convection and radiation were taken into account in this model. The dynamic process of the keyhole and the behavior of the metal vapor inside and outside the keyhole were obtained by numerical calculation. The simulation results show that the morphology of the keyhole was transient, had convex deformation in anterior and posterior and became stable gradually. The size of the keyhole was about 1mm. The keyhole and the metal vapor interacted each other. The greatest vapor velocity was 5.3m/s. A modified "sandwich" novel method was used to conduct laser welding experiment verification. The simulation results matched well with the experimental results. The results show that the level set method to track the free surface of a keyhole in laser deep penetration welding has good adaptability and can provide the theoretical basis for the study of keyhole.