基于平面裁切和材料非线性的ETFE气枕充气成形与结构分析方法研究

The physical states and mechanical model are firstly proposed for the whole process of ETFE cushion integral design, which unevils the coherent mechanical relationship for the sequence of ETFE cushion design, manufacture, installation and operation, respectively. Analyzing the mechanical characteristics of form-inflating-developing of ETFE cushion based on flat-patterning, the form-shaped process is sub-divided into four phases. On the basis of generalized Kelvin-Voigt model and generalized Maxwell model, the shift factor due to temperature change, the corrective function due to various stress, and the nonlinear amplification factor due to plane stress effect, are introduced to the basic linear time-dependent material, and identifying all viscoelastic parameters through series idealized creep test, relaxation test, dynamic viscoelastic experiment and biaxial tension creep experiments, the nonlinear time-dependent model is finally formulated. Adding shrinkage unit and modifying the generalized Kelvin-Voigt model, the time-dependent creep-recovery is formulated sequently and the numerical procedure is realized for the form-inflating-evoluting, as well as inflation procedure and control optimization. On the basis of the developed nonlinear time-dependent mathematic model of ETFE foil, the UMAT is coded through APDL, and the iterative numerical procedure is implemented for form-inflating-developing analysis, structural response analysis and long-term effect evaluation. Series triangular, rectangular and hexgonal ETFE cushion are developed gradually, advanced experiment schemes are proposed and developed to simulate shape-inflating and structural behavior, to measure presicely, and to validate the mathmatic model and numerical method.To combine the theorey and engineering background closely, this will promote structural analysis theory and design technology development of new ETFE membrane structures.

提出ETFE气枕一体化设计全过程的状态、力学模型，揭示ETFE气枕设计、制作、安装、使用过程的内在力学逻辑关系。根据基于平面裁切ETFE气枕充气成形的内在力学机理分析，细分明晰充气成形4个阶段。基于广义Kelvin-Voigt和Maxwell模型，引入温度偏移系数、应力修正函数以及平面应力非线性放大系数，由理想拉伸徐变试验、动力粘弹性试验和双轴拉伸徐变试验的参数表征，建立ETFE薄膜非线性时变模型。通过增加收缩粘弹性单元，修正广义Kelvin-Voigt模型，建立徐变恢复模型，并建立ETFE气枕充气成形非线性分析方法，实现充气成形分析、工艺和控制参数优化。基于所建立的ETFE薄膜非线性时变模型，应用过APDL建立UMAT算法和迭代策略，实现ETFE气枕充气成形、结构载荷响应、长期时效分析。研制三、四、六边形ETFE气枕，设计先进试验方案，分别模拟充气成形、载荷响应，精确测试，验证分析理论。

基于平面裁切和充气成形的ETFE气枕设计方法是一种充分利用ETFE材料粘弹塑性的设计方法，简化裁切、热合工艺流场，节约材料，显著提高生产效率，节约成本。.针对非线性时变模型研究内容，项目通过ETFE薄膜材料系列时间、温度和应力（载荷）相关性的试验，以及短期徐变、松弛、徐变恢复、长期徐变（常温、高温），充分揭示了ETFE薄膜材料的非线性粘弹塑性力学现象及其力学机理，分别基于细观的分子力学、唯象的粘弹塑性力学和广义Maxwell及Kelvin-Voigt模型，并利用试验数据实现参数辨识，分别建立了ETFE薄膜材料非线性时变模型，可以准确考虑率相关性、徐变、松弛和徐变恢复特性，同时引入温度相关系数或温度偏移系数；通过ETFE动力学（DMA）试验，揭示ETFE薄膜的时温叠加效应（TTSP），并通过W.L.F方程表征时温相关性。.针对充气成形分析理论方法，通过ETFE气枕平面充气成形试验、载荷试验和徐变试验，分别进行了三角形气枕常温成形试验，矩形气枕低温成形试验和不同高温（40°、60°）成形试验，结合ETFE非线性时变模型，建立充气成形数值模拟方法及结构设计分析方法。.针对预应力形态与结构响应分析，基于充气成形试验，进行气枕载荷、模态试验，以及结合徐变进行长期时效分析研究。ETFE薄膜集成PV、OPV、LED等构成PV/T或MFM（多功能膜），通过试验和理论及分析，探索研究了光-热-电-结构多物理场问题，及其功能建筑的光热和建筑热物理性能。.通过项目研究，国内膜结构工程领域和学术界逐渐认识并接受了这一新技术，在行业设计指南已推荐可采用ETFE非线性力学模型的分析和设计方法，并为行业规程修订提供了理论基础。

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