铝锂合金蒙皮桁条结构激光焊接残余应力形成机理及航天特种服役环境结构性能评价研究

As a symbol of lightweight structure in the future spacecraft, the laser welded stin-stringer structure of Al-Li alloy takes a tendency to wide application. However, the applications are still limited by deficient research in residual stress distribution and evolution and property change during aeronautics servicing. Considering the DLBSW(dual laser-beam bilateral synchronous welding) technology, the project aims at establishing a coupled thermo-mechanical model considering element damage and microstructure evolution, as well as a property evaluation method of welding structure during servicing process including the defects condition. The distribution and evolution of residual stress and property transformation process during servicing will be deeply explored in this project. The project results provide a theoretical support for the application of Al-Li alloy welding structure in the aerospace industry and enhance the theoretical basis as well..The problems of the following respects are focused:.1.Coupled thermo-mechanical model which consider element damage and organizational evolution is expected for the DLBSW welding process of Al-Li alloy stin-stringer structure. .2.The mechanism of stress formation and evolution in the whole life cycle of Al-Li alloy panel welded structure..3.Microstructure and properties evolution rule of Al-Li alloy welded structure for space panel in the condition of space alternating thermal loading,.4.Property evaluation standard and results of Al-Li alloy welded structure for space panel during special servicing process.

铝锂合金蒙皮-桁条激光焊接结构是未来航天器轻量化结构的发展趋势，但由于面临残余应力分布与演变规律、服役过程性能变化不清晰等问题，限制了其工程应用。本项目基于双激光束双侧同步填丝焊接工艺，提出结合焊接过程元素烧损与组织演变因素的焊接过程热力耦合模型、含缺欠条件下的焊接结构服役过程性能评价方法，揭示典型航天结构的残余应力的分布规律、航天服役条件下的性能演变过程。研究结果将为回答航天领域铝锂合金焊接结构是否“合于使用”提供理论支持，同时也将丰富焊接结构理论基础。.重点解决以下几方面的问题：.1.面向元素烧损与组织变化的铝锂合金蒙皮桁条结构激光焊接过程热力耦合模型；.2.铝锂合金航天壁板焊接结构件产品全生命周期应力形成与演化机理研究；.3.空间交变热载荷条件下的铝锂合金航天壁板结构件组织与性能演变规律；.4.面向航天特种服役环境的铝锂合金蒙皮桁条壁板焊接结构件性能评价准则与评价结果。

本项目针对当今航天器轻量化结构中的铝锂合金蒙皮-桁条激光焊接结构的残余应力分布与演变规律、服役过程性能变化不清晰等问题，主要开展了铝锂合金蒙皮-桁条结构双激光束双侧同步焊接工艺试验，提出了结合元素烧损与组织演变因素的焊接过程热力耦合模型，进行了单桁条试片件，三桁条典型件以及三个典型航天结构件的双激光束双侧同步焊接过程及服役载荷作用下的热力耦合建模及仿真求解。在此基础上，进行了工艺参数-焊接应力状况模型研究，构件“初始状态和服役载荷-空间性能指标”研究以及基于应力数据库和构件生命周期仿真结果的残余应力形成及演化分析等研究，揭示了典型航天结构的残余应力的分布规律以及航天服役环境下的性能演变过程。最终获得了面向元素烧损与组织变化的铝锂合金蒙皮-桁条结构激光焊接过程热力耦合模型，构件产品全生命周期应力形成与演化规律及机理，构件在空间交变热载荷条件下性能演变规律以及面向航天特种服役环境的铝锂合金蒙皮-桁条壁板焊接结构件性能评价准则与评价结果。本项目的研究结果为航天领域铝锂合金焊接结构应用的可行性提供了理论支持，同时也丰富了焊接结构理论基础。