激光+GMAW复合热源焊焊缝成形的数值模拟III.电弧脉冲作用的处理与热源模型的改进

针对激光+脉冲GMAW复合焊时电弧脉冲的热作用特点,将电弧热流处理为脉冲电流和基值电流阶段分布参数不同的双椭圆模式,同时适当减小焊件表面的热导率,以间接考虑脉冲电流和基值电流的间歇式作用.根据平均焊接电流大小确定熔滴热焓椭球体分布的作用区域,并考虑激光热源的作用位置.从以上几方面对前期研究采用的热源模型进行了改进,建立了两类新的适用于复合焊的组合式体积热源模型.利用改进后的热源模型对不同工艺条件下复合焊的焊缝横断面形状尺寸进行了模拟计算.计算得到的熔深、熔宽以及熔合线走向都与实验结果吻合,使数值模拟精度有了较大提高.

NUMERICAL SIMULATION OF WELD FORMATION IN LASER+GMAW HYBRID WELDING III. Treatment of Pulsed Arc Action and Improvement of Heat Source Modes

Considering the thermal action characteristics of pulsed arc in laser+pulsed GMAW (gas metal arc welding) hybrid welding, the arc heat flux is divided into two double-elliptic distribution modes with different parameters corresponding to pulse current duration and base current duration. Meanwhile, the thermal conductivity at the weldment surface is appropriately lowered to take account of intermittent action of pulse and base current indirectly. Based on the level of averaged welding current, the distributed region for double-ellipsoid of droplets heat content is determined, and the action location of laser heat input is taken into consideration. The previous heat source modes have been improved through dealing with the abovementioned aspects, and two new kinds of adaptive combined volumetric heat source modes are developed. The weld geometry and dimensions are numerically simulated under different conditions in hybrid welding process by using the improved heat source modes. The predicted weld penetration depth, width and fusion line locus all agree well with the experimental results. Thus, numerical simulation accuracy for hybrid welding has been greatly improved.