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考虑熔滴和小孔对熔池的影响,建立了基于FLUENT软件的激光+熔化极电弧(GMAW)复合热源焊三维瞬态熔池流体流动数值分析模型.利用双椭球体热源描述电弧热输入,将激光热输入视为热流峰值可调节的双曲线旋转体热源,其热源分布参数通过简化的小孔形状尺寸模型确定;将熔滴过渡过程视为从熔池上部特定区域流入熔池高温液态金属的过程,并通过建立液态金属流速对时间的周期函数表征熔滴过渡频率;将小孔视为由激光致蒸汽反作用力引起的熔池表面变形,以简化计算过程,重点考虑小孔的存在对熔池流体流态的主要影响.利用所建模型对不同焊接条件下的激光+GMAW复合热源焊小孔形态、熔池流体流动和温度场进行模拟计算,分析了激光+GMAW复合热源焊流场特征,探讨了激光功率对复合焊熔池动态行为的影响规律.结果表明,在1 m/min焊速条件下,GMAW焊(激光功率为0 W)出现驼峰缺陷;当激光功率为500 W时,驼峰缺陷消失,但熔池中无小孔产生,且流体流动模式与GMAW焊相近;而当激光功率增至2000 W,熔池中出现小孔,使得流体流动模式更为复杂.将焊缝横断面形状尺寸的计算结果与实验结果进行比较,2者吻合较好,从而证明了模型的准确性和适用性.
Considering the effect of droplets and holes on the weld pool, a numerical simulation model of fluid flow in a three-dimensional transient weld pool based on FLUENT software was established.A dual-ellipsoid heat source was used to describe the arc heat input, The laser heat input is regarded as the hyperbolic rotating heat source whose heat flow peak is adjustable. The heat source distribution parameters are determined by the simplified pore shape and size model. The droplet transfer process is regarded as the flow from the upper part of the molten pool into the hot metal , And the transition frequency of the droplet is characterized by the establishment of a periodic function of liquid metal flow velocity over time; the pinhole is considered as the surface deformation of the molten pool caused by the laser-induced reaction force of steam to simplify the calculation process, with emphasis on the existence of small holes The main influence of the fluid flow state in the molten pool is simulated by using the model. The shape of the holes, the fluid flow and the temperature field in the molten pool under different welding conditions are simulated. The laser + GMAW composite heat source welding flow field Characteristics of laser welding, the influence of laser power on the dynamic behavior of molten pool was discussed.The results show that GMAW welding (laser power of 0 W) The hump defects disappeared when the laser power was 500 W, but no holes were formed in the weld pool, and the fluid flow pattern was similar to that of GMAW welding. When the laser power increased to 2000 W, small holes appeared in the weld pool, Making the fluid flow pattern more complicated.Comparing the calculated results of the cross-sectional shape and size of the weld with the experimental results, the two agree well, which proves the accuracy and applicability of the model.