超高强铝合金精密构件制造过程变形/残余应力演化机理与协同控制

Precision components are key constructional elements of spacecrafts’ sub-system, such as space station's robotic arm, satellite observation/positioning system etc. High shape accuracy as well as high shape stability are urgently needed for obtaining high service accuracy and high reliability. Precision components are usually made from ultra-high strength aluminum alloys through high-speed cutting process, in which the material removal is very large and the structure evolution is quite complicated. Serious distortion is prone to occur in the components during the fabrication, leading to deteriorated shape accuracy. Residual stress has dominating influences on the distortion during fabrication. Computer simulation combined with experimental analysis is used in the research to investigate the principle and mechanism of the residual stress evolution as well as the resulting distortion response under different manufacturing procedures and component shapes. Based on the manufacturing procedure simulation and the artificial neural network, fast prediction method for residual stress evolution and fabrication distortion response can be established, and a database of manufacturing procedure can thus be developed. The research then introduces genetic algorithm to optimize the manufacturing procedure as well as processing parameters, aiming to achieve cooperative controlling on residual stress and fabrication distortion. The finding of this research is important for understanding the distortion as well as for controlling the residual stress/distortion during the whole manufacturing procedure of aerospace precision components. It is believed of technically significance for improving the fabricating accuracy, efficiency and the aerospace components’ service reliability.

航天精密构件主要包括空间站机械臂、卫星观测/定位等分系统中的关键构件，其形位精度及稳定性要求十分苛刻。该类构件选用超高强铝合金作为坯材、经热处理后以机加工方法制造，工序复杂、结构多变，制造过程变形问题突出。本课题针对残余应力是构件在制造过程中产生变形主要原因的问题本质，综合应用计算机仿真和实验研究，深入揭示精密构件制造过程中残余应力演化的规律及机理，以及不同工序、不同形状下残余应力诱发构件变形的规律及机理；在此基础上基于工艺序列系统仿真，应用人工神经网络，建立构件残余应力演化/变形行为的快速预测方法、形成构件制造工艺序列数据库，引入遗传算法对构件制造全过程进行工艺序列优选和工艺优化，实现对精密构件制造过程中残余应力和变形的协同控制，提高精密构件的制造精度和制造效率，降低构件内残余应力、保证构件在服役过程中的可靠性。

大型精密构件是空间站机械臂主承载结构研制基础，其形位精度是影响相关分系统服役性能及可靠性的关键。该类构件均采用超高强铝合金制造，工序复杂、材料去除量大，制造过程中残余应力复杂多变、重分布效应强烈，构件易发生变形且成品构件残余应力较高。这种状况会导致构件制造变形、服役变形等，从而对构件的形位精度和形位稳定性造成显著影响。现行研制工艺下，构件机加工变形超差等问题频繁出现，严重制约了构件高效制造及可靠服役。针对关键构件形位控制难题，瞄准制造变形问题的根源、开展残余应力/形位演化与控制技术的研究成为该类构件研制的关键。. 本项目针对残余应力全过程演化、遗传效应显著的因素，以残余应力仿真为基础开展制造全过程残余应力演化及其形性响应规律的研究。项目建立了制造全过程仿真分析平台以及喷射沉积7055铝合金本构与热物参数数据库，实现了 “淬火-时效-机加工”全过程的残余应力/形位演化自动仿真；基于系统比对对仿真系统进行了充分验证，证实了其准确性。基于仿真分析，揭示了结构特征与工艺参数影响残余应力及变形响应的规律；研究证实，在20~80oC范围内提高淬火水温可以显著降低坯材残余应力，而消除表面位置的凹槽结构可以抑制表面拉应力。组织表征及第一性原理模拟显示，适当提高淬火水温可以在显著降低残余应力的同时不显著改变合金析出行为、从未保证材料的强塑性；经典型低应力淬火工艺处理，坯材强度、塑性均满足设计要求。实现了加工过程“切削序列—应力/应变”序列的全过程数据衍生，引入遗传算法建立了去除序列的系统优化，使机加工变形降低30%以上。基于本项目取得的方法开展了空间站基座本体等构件的研制，通过结构优化以及淬火、机加工等工艺环节的优化，使的本体基座主要形位特征变形超差降低70%以上。相应的构件已经成功研制、并应用于空间。. 项目实施期间发表文章15篇，其中SCI收录10篇；申报专利10项，其中国际专利3项；获批软件著作权1项；培养研究生13名。