大型飞机高性能铝合金整体壁板双光束激光压焊机理与工艺研究

Developing large aircrafts is an important national strategic decision. It is demanded that the design and manufacturing of aircraft structures should be satisfied with respect to weight savings, performance improvement and cost reduction. To fulfill such requirements, the application of laser beam welding in manufacturing of integral fuselage panels of new high-performance aluminum alloys has become a trend in the aircraft industry. The laser-welded panels of high-performance aluminum alloys, however, still suffer from serious limitations like the shortage of strength and toughness, and the greater structural distortions. In this project, to overcome those inherent limitations of conventional laser fusion welding processes, a novel approach, namely dual-beam laser pressure welding, is proposed for the manufacturing of aircraft integral panels of aluminum alloys. The aims of the project are: (1) to build up the theoretical frame of laser pressure welding, based on the intensive research on the understanding of physical processes, such as the laser energy transfer and absorption laws in the groove of the joint (in which a new theoretical model of laser energy absorption will also be created in view of quantum effects of valence electrons), laser-induced plasma behavior characteristics in the limited space of the groove, appropriate welding conditions and joint bonding mechanism; (2) to establish the corresponding technical system of dual-beam laser pressure welding of integral fuselage panels of high performance aluminum alloys by fully exploring the welding process, the defect formation mechanisms, the microstructures and joint properties.

研制和发展大型飞机是国家的一项重要战略决策。采用激光焊接技术制造新型高性能航空铝合金整体壁板是大型飞机结构轻量化、高性能化和低成本制造的一种发展趋势,但是传统激光熔焊方法仍然存在接头强韧性不足、焊接结构变形大等瓶颈问题，尚不能满足新型高性能铝合金整体壁板焊接制造的要求。本项目申请人提出采用双光束激光压焊新方法，有望突破传统激光熔焊制造方法的固有局限。项目将系统深入地研究激光压焊坡口的光波导行为及能量耦合规律、受限空间内的光致等离子体行为特性、激光压焊优化工艺条件、接头结合机理，创建考虑价电子量子效应的激光能量吸收新的理论模型和激光压焊理论体系；构建双光束激光压焊实验平台，深入研究高性能铝合金整体壁板双光束激光压焊工艺、缺陷形成机理、接头组织性能等，为激光压焊在我国的创新发展和应用奠定理论和技术基础。

围绕大型飞机新型高性能铝合金整体壁板激光焊接制造中存在的接头强韧性不足、焊接结构变形大等瓶颈问题，项目申请人提出了铝合金激光双光束压焊方法，并针对：“ (a) 激光压焊坡口的波导行为及吸收特性；(b) 坡口内光致等离子体特性及其对激光能量传输与耦合的影响规律；(c) 激光压焊焊缝成形特点及结合机理；(d) 高强铝合金薄壁T型构件双光束激光焊接变形规律与控制”这四个方面开展了系统的理论和实验研究工作。. 本项目基于几何光学、光线追踪法和菲涅尔吸收原理，建立了激光在V型坡口内传输与能量耦合理论计算模型，揭示了铝合金激光压焊坡口内激光的波导行为、激光能量耦合机制、材料的熔化行为。基于不同波长激光焊接铝合金的深熔阈值特征，研究了光致等离子体的行为及其对激光能量传输与吸收的影响规律；通过铝合金压焊焊缝横截面和不同纵截面晶粒形貌、织构及晶粒间小角度晶界比例的表征，分析不同焊缝截面所经历的熔化凝固过程以及受到压力后的晶体转动情况，从而揭示了铝合金激光压焊焊缝的成形机理；根据高强铝合金T型构件双光束激光同步焊接热力过程的特点，修正了现有激光深熔焊热源模型的计算方法，提出并实施了双光束激光同步焊在蒙皮背部随焊辅助热源+辅助激冷的方法，有效地实现了角变形和残余应力的同时控制。. 本项目执行顺利，在研究内容、研究目标、研究预定成果等方面均基本完成任务。在本项目资助下，已发表学术论文共10篇，其中SCI检索论文7篇；申请国家发明专利1项，参加国内外会议并作口头报告共10次；培养硕士和博士研究生合计4名（含硕士毕业1名、博士毕业1名，博士在读2名）。