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基于流体动力学原理,同时考虑电弧压力、表面张力、电磁收缩力、浮力和重力等因素影响,建立了随小孔深度增加热力作用二次变化的三维瞬态计算模型.利用上部双椭球体下部锥体的组合式体积热源描述等离子电弧对焊接工件的热作用,提出了可以维持小孔稳定的“孔内固体搅动式”计算方法.为了提高计算效率,建立了相对焊缝纵截面对称的计算区域;计算过程利用流体体积函数(VOF)法追踪小孔边界,基于FLUENT软件对穿孔型等离子弧准稳态焊接过程进行了数值模拟,得到了准稳态焊接过程中小孔、熔池及流场的动态变化行为,分析了穿孔型等离子弧焊接(K-PAW)准稳态过程的稳定性,探讨了影响小孔稳定的工艺因素,最后进行了计算模型的验证实验.结果表明,在设定的焊接工艺参数下,3.0 s之后焊接过程达到准稳态,准稳态焊接过程中小孔前壁熔池较薄,平均厚度为0.6 mm,且小孔前壁有一定倾斜现象,使得背面小孔中心相对焊接中心向后偏移,焊接不同时刻偏移量在0.46~0.97 mm之间波动.在准稳态焊接过程中熔池内存在稳定的逆时针涡流,计算所得的背面小孔宽度与实验结果吻合良好.
Based on the principle of fluid dynamics and taking into account the influences of arc pressure, surface tension, electromagnetic force, buoyancy and gravity, a three-dimensional transient model was established with the secondary change of thermal effect with the increase of pore depth.Using the lower part of the upper double ellipsoid The combined volumetric heat source of the cone describes the thermal effect of the plasma arc on the workpiece, and proposes a method to calculate the “intra-hole solid-agitation” method that can maintain the stability of the hole. In order to improve the computational efficiency, . The calculation process uses the fluid volume function (VOF) method to trace the hole boundary. Based on FLUENT software, the quasi-steady state welding process of the pierced plasma arc is numerically simulated. (K-PAW), the stability of the quasi-steady state of P-type plasma arc welding (K-PAW) was analyzed, and the process factors affecting the stability of the pores were discussed. Finally, the verification experiments of the calculation model were carried out. Under the set welding parameters, the welding process reaches the quasi-steady state after 3.0 s, and the molten pool in the quasi-steady state welding process is thin with an average thickness of 0.6 m m, and the front wall of the hole has a certain inclination phenomenon, so that the center of the back hole is offset backward relative to the welding center, and the offset varies from 0.46 to 0.97 mm at different times of welding. In the quasi-steady state welding process, The stability of counter-clockwise eddy current, the calculated width of the back hole coincides well with the experimental results.