大厚度铝合金T型接头激光+GMAW复合焊熔池气/液界面热力耦合机制及流体流动研究

ABSTRACT: In laser+GMAW hybrid welding of thick aluminum alloy T-joint, weld defects are more easily generated when mismatching welding parameters, leading to poor quality stability. The feature of heat and stress distrisbution on vapor-liquid interface can affect thermal field and weld pool behaviour and then the weld formaiton. Thus, in order to eliminate welding defect, it must first analyze the thermodynamic characteristic on vapor-liquid interface of weld pool. This project aims to study the thermo-mechanical coupling mechanism on vapor-liquid interface of weld pool in hybrid welding of thick alluminum alloy for T joint by combining the numerical calculation and experimental detection based on mechanisms of optics, electricity, heat transfer and fluid dynamics after consdiering the joint pattern and therophysical property of base matal. The discrete heat flux distribution model and three dimensional analysis models for keyhole and fluid flow in hybrid welding of T-joint will be developed to analyze the thermo-mechanical coupling mechanism and its influence on weld pool behavior, revealing the generation mechanism of welding defect, including pore, undercut, incomplet penetration and fusion and the supression measure will be put forward. The correlation among the welding paramters, therodynaic characteristic on vapor-liquid interface, weld pool behavior and weld formation is determined, realizing the initiative adjustment and control of welding quality and thus increasing the stabiliy and reliability of hybrid welding for the complex jiont and weldment of thick aluminum alloy.

大厚度铝合金T型接头激光+GMAW复合焊时，若参数配合不当，更易出现焊接缺陷，质量稳定性较差；熔池气/液界面热/力分布特征直接影响焊接热场及熔池形态，继而影响焊缝成形；故消除焊接缺陷，必须首先对熔池气/液界面热力学特征进行准确分析。本项目拟采用数值计算与实验检测相结合的方法，依据光学、电学、传热学及流体动力学机理，综合考虑接头形式及材料热物理特性，研究大厚度铝合金T型接头复合焊熔池气/液界热-力耦合机制，建立T型接头复合焊离散式热流分布模型及小孔、熔池流体流动三维数值分析模型，定量分析了熔池气/液界热-力分布特征及其对熔池动态行为的影响机制，揭示铝合金T型接头复合焊气孔、咬边、未焊透/未熔合等焊接缺陷的产生机理，提出抑制措施，确立工艺参数-气/液界面热-力特征-熔池动态行为-焊缝成形的相关性，实现对焊接质量的主动调控，提高大厚度铝合金复杂接头及焊件复合焊的稳定性及可靠性。

相较于简单接头，铝合金T型接头激光+GMAW复合热源焊更易出现焊缝缺陷，焊接质量的稳定性和可靠性相对较差。针对该问题，本项目对铝合金T型接头激光+GMAW复合热源焊气/液界面热-力耦合行为及熔池内流体流动进行研究，揭示焊缝成形缺陷产生的物理机制，为大厚度铝合金T型接头复合热源焊接工艺优化和实际应用奠定坚实基础。. 依据研究计划，本项目通过实验检测和数值模拟相结合的方法，深入开展了铝合金T型接头激光+GMAW复合热源焊熔池热力特征和焊缝成形机理研究工作。综合考虑接头几何特征和电弧等离子体与光致羽辉相互作用，建立T型接头激光+电弧复合热源焊电弧物理特性数值分析模型；结合实验检测和模拟计算结果，分析了工件及熔池表面热流和应力分布特征及两者耦合机制，探明了激光功率、电弧功率等不同参数对其影响规律。. 以此为基础，考虑材料物理特征、热流及应力动态分布特性、电弧-熔滴-小孔-熔池相互作用，建立了铝合金T型接头激光+GMAW复合热源焊多相耦合数值分析模型。基于实验和计算结果，揭示了铝合金平位置T型接头复合焊熔池热场、流场及小孔动态行为特征，阐明了不同工艺参数对其影响机制及焊缝成形机理。从复合热源热力分布特征及小孔、熔池动力学特性角度，探究了气孔、驼峰及咬边等焊接缺陷的产生和抑制机理；建立了“工艺参数-熔池热力特征-小孔/熔池行为特性-焊缝成形”相关性；从调节熔池热力分布特征角度，提出了铝合金T型接头复合焊焊缝成形的调控措施，继而提高了焊接质量的可靠性。本项目研究成果有助于深入、全面理解铝合金T型接头复合焊内部物理机制，这对于高反射率、高性能合金复杂接头激光+GMAW复合热源优质、高效焊接，促进我国轻量化装备制造的发展，具有重要的学术价值和工程实用价值。