摘    要   作为一种轻质材料，铝合金密度低、强度高、热电导率大、耐腐蚀能力强，因而铝合金的焊接结构被广泛应用于工业产品。作为一种新型焊接工艺，激光+GMAW复合热源焊综合了激光焊和GMAW焊的双重优点， 克服了两者的不足，且产生了额外的能量协同效应，具有实现铝合金优质、高效焊接的巨大潜力。但激光+GMAW复合焊较单热源焊，其工艺参数较多，难于优化，阻碍该工艺的推广应用。焊接过程中，熔池内流体流动与焊缝成形密切相关，因此，深入了解铝合金激光+GMAW复合焊焊缝成型机制，有助于促进该工艺在铝合金焊接中的推广应用。 本文综合考虑铝合金热物理性能和复合焊工艺特点，基于 FLUENT 软件，建立了适用、高效的铝合金激光+GMAW复合热源焊三维瞬态熔池流体流动数值分析模型。该模型综合考虑了电弧热输入、激光热输入和熔滴热焓三者之间的耦合作用； 利用双椭球热源模型描述电弧热输入；用锥形热源模型描述激光热输入；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； 依据蒸汽反作用力的作用确定小孔形态。 用该模型对不同工艺参数下的铝合金激光+GMAW 热源复合焊接的热场和流场进行模拟计算，并将焊缝尺寸与实验结果比较，从而使模型得到验证和优化。结果表明：当激光功率为 3000W 时，熔池尺寸较小，小孔深度较浅；小孔前壁金属始终向熔池底部流动，而熔池后壁附近金属流态相对复杂；当激光功率为5000W 时，熔池小孔处于动荡过程重复出现小孔产生和闭合。小孔前壁金属流向小孔底部，然后再流向熔池后部，或沿厚壁向上流动；小孔后壁金属流向与小孔深度及动态行为相关。 58957
毕业论文关键词：铝合金；激光焊；GMAW；复合焊；热源模型；熔池形态
Abstract Aluminum alloy has the features, including  low density, high strength, large thermal conductivity, corrosion resistant capability is strong,  Thus the welding of aluminum alloy structure is widely used in industrial products. As a new type of welding process, Laser+GMAW welding composite heat source combines laser welding and the double advantage of GMAW welding,  and  overcomes  the disadvantages of both, and produces the additional energy synergy effect, and is with implementation of aluminum alloy the great potential of high quality, high efficiency welding. But the laser+GMAW composite brazing a single heat source, and there is a lot of process parameters which is difficult to optimize, and those hinder the process of popularization and application. Comprehensive consideration of  aluminum  alloy composite thermal physical properties and welding process characteristics, based on    FLUENT software, laser+GMAW is established, the highly effective aluminum alloy composite three-dimensional transient heat weld pool fluid flow numerical model. The model considers the arc heat input and laser heat input and the coupling effect between and among thermal enthalpy drop; Double ellipsoid heat source model is used to describe electric arc heat input; Using the conical heat source model to describe thermal input; Will drop as a transitional process from the molten pool of a particular area of liquid metal flows into the molten pool temperature process; According to the role of vapor reaction determine the pore morphology. With the model of aluminum alloy under different process parameters with the laser+GMAW composite welding heat source of thermal field and flow  field numerical simulation, and compared with the experimental results, the size of the welding so that the model is verified and optimized. The results showed that: when the laser power is 3000W, the small size of molten pool, the shallow hole depth; holes front wall metal has always been to melt the bottom flow of the molten pool near the back wall of metal flow is relatively complex; when the laser power is 5000W, molten pool holes in repeated hole instability process and closed. small hole at the bottom of the front wall of metal flow and then at the back flow of molten pool, or along the thick wall upward mobility; after hole wall metal flow is associated with small hole depth and dynamic behavior.  铝合金激光+GMAW复合热源焊熔池形态的分析:http://www.751com.cn/cailiao/lunwen_63981.html