气肋膜结构动态折叠建模方法研究

Dynamic folding study of air-inflated rib membrane structure

建立充气膜结构初始瘪气状态的折叠模型是进行充气仿真的基础.动态泄气倒塌分析是获取复杂结构初始折叠模型的基本建模方法之一.以气肋膜结构为例,基于控制体积法,研究了有限元分析中单元类型、数量及三种倒塌算法对计算效率、折叠效果及单元变形等的影响.结果表明,三角形膜单元计算耗时少,但计算结果收敛慢;随单元数量上升,计算耗时呈非线性快速增长,收敛效率则呈非线性递减;压应力消除法倒塌计算慢、体积压缩困难、表面积收缩大,不适于建立初始折叠模型;过载法计算快、体积压缩极快、表面积变形极小,可用于建模,但折叠形态不佳;在综合应力消除法和过载法的基础上,提出适于建模的混合法,实现了较优的计算效率和单元变形控制,且折叠形态较自然.

Achieving folded model of inflatable membrane structure is the first step of inflation simulation. Dynamic collapse analysis is one of the folding methods to deal with complex structures. Based on control volume method, a series of air-inflated rib membrane structures are studied, which include researches of computational efficiency, folded quality and element deformation of different finite element types, element quantity and three collapsing algorithms. Analysis shows that triangular element is less time-consuming while with lower convergence efficiency. When element quantity increases, calculation time rises non-linearly and convergence efficiency decreases non-linearly. Compression stress elimination method is not good for creating folded model with time-expensive calculation, slow volume compression and large shrinkage of surface area. Over loading method provides a feasible way to perform fast collapsing with excellent volume compressibility and extremely small deformation of finite elements except for its unrealistic surface appearance. A mixed method is proposed, which integrates advantages of both above methods and presents potential of better folding performance with acceptable efficiency and deformation,and more importantly a natural shape of deflated surface.