小孔等离子弧焊接热场的有限元分析

Finite element method analysis of temperature field in keyhole plasma arc welding

根据小孔等离子弧焊接的工艺特点,建立了相应的热源模型和焊接热场的分析模型。数值模拟结果表明,一般的双椭球体热源和三维锥体热源不能准确描述小孔等离子弧焊接热过程。提出了改进型的三维锥体热源模型,可以较准确地计算焊缝的正面和背面熔宽,但熔合线走向的计算精度仍较低。在此基础上,考虑等离子弧对熔池的热-力作用,建立了符合小孔形态的热源模型,对小孔等离子弧焊接热场进行了有限元分析,计算出的小孔等离子弧焊缝形状与试验结果吻合良好。

The models of both heat source and welding temperature field were developed according to the characteristic of keyhole plasma arc welding (K-PAW) process. The result of numerical simulation indicated that neither general double ellipsoidal heat source nor three-dimensional conical heat source could precisely describe the thermal process in K-PAW. A modified model of three-dimensional conical heat source was put forward. It could be used to calculate the weld width on both the top and the bottom surfaces of the workpiece exactly. But for the fusion line, the calculating precision was lower. Based on the theoretical analysis of keyhole and weld pool behaviors, a novel heat source model was employed which considered the combined action of both heat and force from the plasma arc. Finite-element analysis of the temperature fields in K-PAW was conducted, and the calculated geometry result of K-PAW weld geometry was in agreement with experimental result.