大型铝锂合金薄壁构件电辅助双面多点增量成形材料流变行为及工艺研究

Aluminum lithium alloy material for large thin-walled structures on aerospace has poor plasticity and formability at room temperature. The traditional incremental forming technology has limited deformation modes and strong effect of local deformation and internal stress. As a result, it is difficult to reflect the overall structure from the precision of local plastic deformation and the precision of overall structure is further influenced. Therefore, the manufacturing technology for large thin-walled structures of aluminum lithium alloy is urgent to overcome. The electrical-assisted effect is introduced and the double-side multi-point incremental forming method is proposed for large thin-walled structures of aluminum lithium alloy. The formability will be enhanced and the precision of large structure are expected to be improved by a variety of deformation modes optimization. Based on material rheological behavior control in the forming process,the electrothermal effect and electroplastic effect introduced by electric field are studied and quantitatively described. The inherent mechanism to improve the formability is revealed and the material forming limit criteria under local cycle-load and electricity-thermal-force couple is developed by investigating the effect of material partial softening in electrical-assisted condition.The multi- fields coupling simulation model for the electrical-assisted double-side multi-point incremental forming process is developed and the influence law of electric filed distribution and load path is obtained. The forming quality indicators are proposed and methods of process design and optimization are established for electrical-assisted double-side multi-point incremental forming process. Furthermore, the experimental prototype is setup and experiments are systematically carried out. The theory and method for the accurate manufacture of large thin-walled structures of aluminum lithium alloy are achieved through this proposal.

大型航空铝锂合金薄壁构件材料室温塑性差，成形困难；传统增量成形技术变形方式单一，局部形变与内应力效应明显，导致局部塑性变形精度难以反映到整体构件，影响构件整体精度，其制造技术亟待突破。 本项目引入电辅助效应，提出大型铝锂合金薄壁构件双面多点增量成形新方法，改善其成形性能，实现多种变形方式优化，提高大型构件成形精度。围绕成形过程中材料流变行为控制，研究电场引发的电热与电致塑性效应，实现对电场电热和电致塑性效应的定量描述；探究电辅助条件对材料产生的分片局部软化效应，揭示成形性能提高的内在机理，建立局部循环载荷下电-热-力耦合的材料成形极限准则；通过大型薄壁构件电辅助双面多点增量成形多场耦合仿真建模，获得电场分布和加载路径的影响规律；提出大型薄壁构件成形质量指标，建立电辅助双面多点增量成形工艺设计与优化方法，并构建实验原型系统，为大型铝锂合金薄壁构件的精确制造提供理论与方法。

大型航空铝锂合金薄壁构件材料室温塑性差，成形困难；传统增量成形技术变形方式单一，局部形变与内应力效应明显，导致局部塑性变形精度难以反映到整体构件，影响构件整体精度，其制造技术亟待突破。 .针对上述材料和工艺问题，本项目将电热效应和电致塑性效应引入局部加载增量成形中，提出电辅助双面多点增量成形工艺，籍以降低成形力、提高成形性能，实现铝锂合金材料大型复杂薄壁零件的高精度加工。本项目主要完成工作为：. 围绕成形过程中材料流变行为控制，研究了高密度脉冲电流条件下铝锂合金板料的弹塑性力学行为：通过电辅助单拉以及高温拉伸实验，研究电流场、温度场以及其耦合作用下对材料流动性能的影响并构建了高密度脉冲电流下材料的本构模型；探究电辅助条件下引入的电致塑性效应以及焦耳热效应等对材料成形极限的影响，建立了电-热-力耦合条件下材料成形极限准则，揭示成形性能提高的内在机理；研究电辅助双面多点增量成形多场耦合仿真建模方法，获得电场参数和加载路径对成形性能的影响规律；提出大型薄壁构件成形质量指标，分析比较包括加载路径、电场参数等在内的工艺参数对成形质量的影响,构建了实验系统并开展相应实验研究。.本项目研究工作中提出的电辅助双面多点增量成形新工艺，可实现多种变形方式，改善了铝锂合金的成形性；构建高密度脉冲电流作用下的铝锂合金材料本构模型，综合考虑了高密度脉冲电流下电热效应、电致塑性效应及其耦合规律，实现了材料流变行为的精确描述；开发电辅助双面多点增量成形工艺实验平台，建立了铝锂合金增量成形极限，并进行成形质量评价方法研究，为大型铝锂合金薄壁构件局部结构的成形提供了理论支持与技术指导。