球形高筋壁板渐进模压变形缺陷调控与加载路径优化

Spherical shaped integral panels with high convex stiffeners are the main load-bearing structures of the node cabin in manned space station. Because of its structural complexity, large deformation and the demand of forming quality, the components are difficult to be formed qualifiedly using the present forming methods for integral panels. In this project, with the combination of the die forming and incremental bending forming, a new technology named point on point incremental die forming is developed in order to form the spherical shaped integral panels with high quality, short cycle and low cost. The research focuses on the below scientific issues of the new technology: (1) the deformation coordination mechanism of intersecting structure of skin and stiffeners during incremental die forming process, (2) theoretical calculation model of existing multi-direction bending springback, (3) evolution of deformation damage mechanism of high convex stiffeners with large deformation. The main research contents are as follows: (1) uneven material flow behavior and critical condition calculation of deformation defect, (2) analytical model of the multi-direction bending springback and calculation of load parameters, (3) formation mechanisms and laws of both residual stress and deformation damage, (4) precision process control of incremental bending forming for spherical integral panels. The formation mechanism of deformation defects, effects of parameters on springback and deformation damage mechanism will be revealed. The research results will supply technical guidance for the shape forming and performance control of the technology. The research has an important academic significance to enrich the plastic forming theory for integral panels. The proposed new technology is great helpful to manufacture the node cabin of space station effectively.

球形外凸高筋整体壁板是载人航天空间站节点舱的主结构件，由于其结构复杂、变形曲率大及成形质量要求高，现有的整体壁板成形工艺难以制造出合格零件。本项目将模压成形与渐进压弯工艺相结合，提出一种逐点渐进模压成形的新工艺，以实现对球形外凸高筋整体壁板高质量、短周期和低成本精确成形制造。围绕逐点渐进模压过程中筋条和蒙皮交叉结构的变形协调机制、多向弯曲加载条件下回弹理论、多道次增量加载路径下变形损伤演化机制等科学问题，从高筋壁板成形过程非均匀材料流动分析及临界条件计算、多向弯曲回弹模型与加载参数计算方法、残余应力与变形损伤形成机制及影响规律、球形壁板渐进模压成形工艺调控方法等方面开展研究，揭示球形外凸壁板渐进模压结构缺陷形成机理、回弹及变形损伤规律，为工艺过程的形、性优化调控提供相应的理论指导。项目研究成果可丰富整体壁板的塑性成形理论和工艺技术，为我国航天空间站节点舱研制提供制造技术保障。

本项目针对我国空间站节点舱的大尺寸球形外凸高筋整体壁板成形制造难题，提出并开发了一种使用小尺寸模具逐点渐进模压的柔性成形工艺。结合理论、有限元仿真和试验方法，针对渐近模压工艺的失稳预测与控制，交叉筋条回弹，变形损伤与残余应力调控、多道次模压工艺规划与参数计算等关键科学问题进行了系统研究。基于渐近模压过程中筋条和蒙皮的材料流动和应力分布，提出了一种考虑剪应力和应变强化的临界失稳条件计算方法；提出了一种综合考虑截面反弯矩和蒙皮内弹性应变释放的交叉筋条结构回弹计算方法，并能计算完全下压和中间道次未完全下压回弹后的筋条轮廓形状；采用适用铝合金拉伸剪切复合变形状态的韧性断裂准则计算变形损伤，基于统计学方法分析变形损伤和残余应力分布，为模具尺寸和加载量的形性调控提供评价指标；基于最小塑性功原理提出了渐进模压成形时中间道次的构型设计方法，综合考虑失稳极限、回弹、变形损伤和残余应力，提出了渐近模压工艺设计流程及工艺参数设计方法；基于ABAQUS软件开发了变形损伤计算、模压快速建模和多道次模压轨迹设计等专业插件，实现了节点舱大型球形壁板的逐点渐近模压复杂工序过程有限元仿真和参数优化；进行了多边形典型件及大尺寸球形壁板1:1渐近模压生产试验，成形制造了合格的大尺寸球形高筋壁板零件，验证了模压工艺设计方法的有效性。本项目解决了交叉高筋壁板渐近模压过程中缺陷预测、成形质量调控和工艺设计的难题，研究成果为型号节点舱研制提供了实用的工艺方法和技术支撑，也为未来空间站双曲率高筋壁板高精度高质量制造积累了技术基础。