考虑裁切效应的膜结构找形优化与全过程精确分析理论研究

The analytical states and numerical computation procedures are firstly proposed for the whole process of membrane structures. On the basis of form finding and cutting of standard design method, the 2D cut panels are mapped to 3D surface with transformation technique, introducing accurate constitutive of membrane, the form finding optimization considering patterning is developed through Update Reference Strategy, which is subjected to minimization of 'stress difference' energy. By prestress releasing, the idealized zero-stress state is calculated iteratively with specific stress field and constitutive law taken into account. In addition，the cutting and patterning method is considered, as well as the effects of surface undevelopability, the constructed zero-stress state is computated sequentially with Update Reference Strategy. Based on the idealized zero-stress state, the prestress developing analysis is established, and the prestress developing mechanism is evaluated thoroughly. Furtherly, on the basis of the constructed zero-stress state, assuming the multi particale-spring system, the forming analysis is proposed through the Euler integration of kinetic equation, which include membrane slack, wrinkle and self-interfere action. Based on the prestressed state, considering high therm and therm-wind coupling, the advanced structural behavior is investigated comprehensively for the mechanically stressed and penumatic-stressed membrane, respectively. Costa's tensile surface and three-layer ETFE cushion prototype with thin film photovoltic will be manufactured respectively. The advanced test-up needs development to testify the forming, stress releasing and developing through high precision surveying of form and stress field, and finally demonstrate the theoretic algorithm. To implement the computation algorithm, computer code will be developed accordingly. The close combination of theory and engineering application will promote the development of structural analysis theory and design technology of new membrane structures.

提出膜结构设计分析全过程的数理状态、数理分析模型；基于膜结构初次找形、裁切，建立2D膜裁片3D膜面映射关系，引入膜精确本构，以应力偏差能量最小为目标函数，应用修正位形方法，建立考虑裁切效应的膜找形分析优化理论；根据找形优化平衡形态，考虑膜本构、应力场，通过预应力释放分析求理想零应力态；以找形优化平衡态为基础，考虑裁切方法及效应，通过位形迭代应力释放求构形零应力态；基于理想零应力态，建立预应力导入分析方法，研究预应力导入机理；基于构形零应力态，采用多质点-弹簧模型，考虑膜松弛褶皱和自接触，应用欧拉法求解，建立成形分析理论，研究成形机理与形态控制方法；基于预应力态，考虑多场耦合，研究膜结构精细行为特征。研制Costa曲面张拉膜、三层ETFE气枕，设计先进试验方案，分别模拟膜面成形、应力导入，精确测试，验证分析理论。针对所研究理论开发软件，将理论与工程结合，促进膜结构设计分析理论和技术发展。

薄膜航天器、浮空器以及新型建筑膜结构对其形态和安全性具有高于一般建筑膜结构的技术要求，须采用精细设计分析方法以实现“控形控性”。.项目提出和完善了膜结构全过程精细设计方法，基于找形、裁切、焊接、张拉/充气成形的物理过程，定义其物理状态及过程力学模型，提出12个状态9个过程分析；将膜面等效为膜线，基于找形平衡形态几何和应力，考虑膜材精细本构模型，采用M-P广义逆求最优解，通过释放边界和泄压模拟，迭代计算零应力态；基于找形平衡态，采用测地线裁切，由节点不平衡力最小展平膜面（3D至2D），考虑大转动、大位移、小应变，将2D膜裁切片“张拉”至3D测地线，构建新找形平衡形态，从而实现考虑裁切效应的成形过程分析。.膜材的力学行为和本构模型是准确分析膜结构形态和响应的基础。项目完善了多功能双轴拉伸试验机系统及测试和分析方法，建立了以双轴拉伸为核心的织物膜材测试方法，包括双轴拉伸弹性常数、双轴剪切、双轴撕裂、双轴拉伸强度，并以此为基础建立织物膜材的弹性力学模型、应力空间相关性非线性力学模型及残余应变模型、剪切力学模型，并应用于膜结构技术规程及飞艇结构设计；ETFE为热塑性薄膜，进行不同应变率等温拉伸试验、高低温试验、低周循环试验、徐变试验、徐变恢复试验、DMA试验、高温徐变试验等，深入揭示ETFE薄膜率-温度-时间相关非线性力学行为机理与特征，分别基于经典粘弹塑性力学理论模型、高分子理论、广义Maxwell模型、Kelvin-voigt模型，研究了ETFE薄膜非线性力学模型，包括：率相关模型、时温相关模型、徐变模型等。.针对复杂构型充气尾翼、椭球飞艇、四边形PV-ETFE气枕、三角形ETFE气枕等，研制了试验模型、无接触摄影形态测量系统，测试了热载荷、均匀外气压、激振作用下膜结构的变形、应变、动态响应，验证了材料本构模型、数值分析方法。.项目研究成果对膜结构精细设计及相关基础理论重要具有推动作用。