柔性网增强充气梁的弯皱耦联行为研究

The interactive buckling is a key issue to perform the failure analysis and loading capacity design of inflated beam. The challenge in the theoretical analysis is how to understand accurately the interactive and coupled effects on the post-buckled modes. The study is focused on the flexible mesh reinforced inflatable beam in this project. The theoretical and experimental studies are performed on three key contents, the interactive bending-wrinkling behavior of inflated beam, the constitutive relation for flexible mesh reinforced membrane, and the failure mechanism of buckled inflatable beam. Firstly, the nonlinear buckling control equations of inflated beam are established to analyze the post-buckled wrinkling characteristics and its interactive effects on the large bending deflection. Secondly, a three-node thin-walled tube element is established to discrete the buckling theory. Based on the numerical theory, the full-range buckling analysis is performed to track the post-buckled bifurcation paths and to elucidate the interactive effects on the post-buckled modes. Thirdly, a mechanical model of representative volume element is established to determine the constitutive relation for flexible mesh reinforced membrane based on the energy method and the lamination theory of composite material. Fourthly, the bending-wrinkling and failure behaviors of flexible mesh reinforced inflatable beam are studied. Finally, the mechanical properties of flexible mesh reinforced membrane and the bending-wrinkling characteristics of inflated beam are tested using non-contact measurement methods. Several possible novel achievements will be obtained from the studies on the interactive buckling and failure mechanism of inflated beam. These studies and results will provide a significant support to understand the mechanical behavior of inflated structures.

相关屈曲问题是充气梁失效分析与承载设计中的关键问题，如何准确理解屈后失稳模式的关联与耦合效应是理论分析中的难点。本项目以柔性网增强充气梁为研究对象，重点针对充气梁弯皱耦联行为、柔性网增强膜材的力学本构关系、充气梁皱曲失效机制三个核心问题开展理论与实验研究。首先，建立充气梁的非线性屈曲控制力学模型，分析屈后褶皱特性及其与大挠度弯曲的耦联性。然后，建立三节点薄壁管单元模型并离散屈曲控制方程，进行充气梁屈曲的全过程数值分析，追踪后屈曲分叉平衡路径，进行屈后失稳模式的关联性分析。之后，建立柔性网典型单胞力学模型，基于能量法和复合材料层合理论确立柔性网增强膜材的力学本构关系。随后，进行柔性网增强充气梁的弯皱及失效行为分析。最后，进行柔性网材料性能与结构皱曲行为的实验测试。本项目争取在屈曲关联性与失效机制研究方面取得一定的创新性成果，为丰富充气膜结构的力学基础理论研究奠定基础。

相关屈曲问题是充气梁失效分析与承载设计中的关键问题，如何准确理解屈后失稳模式的 关联与耦合效应是理论分析中的难点。本项目以柔性网增强充气梁为研究对象，重点针对充气梁弯皱耦联行为、柔性网增强膜材的力学本构关系、充气梁皱曲失效机制三个核心问题开展理论与实验研究。取得的重要成果如下：（1）建立了充气梁在均布载荷作用下的三点受弯皱曲失稳力学理论模型，确定了充气梁受弯皱曲失稳和kink失效的判定准则，预报了充气梁临界皱曲和临界kink弯矩，获得了充气梁结构参数、边界条件和载荷变化对皱曲失稳与kink特性的影响规律。（2）建立了充气梁整体与局部耦联失稳力学理论模型，明确了整体屈曲与局部皱曲特征的耦联关系，提出了基于慢变傅里叶和牛顿可信域方法的充气梁局部与整体耦联失稳的求解方法，分析了充气梁皱曲失稳后褶皱演化特性，预报了结构特征参数和边界条件等对充气梁皱曲与kink特征的影响。（3）建立了任意曲梁虚拟等代充气梁的屈曲力学理论模型，采用虚拟梁模型结合曲梁模型分析了充气拱的面内与面外屈曲特性。针对三点弯曲充气梁的弯皱特性，建立了多尺度分析模型，数值分析了褶皱发生、扩展规律和承载特性。建立了基于传递矩阵的变截面充气梁屈曲分析的多尺度数值模型，完成了变截面充气梁的大变形非线性弯曲分析，获得了变截面充气梁的起皱载荷与失效载荷。（4）建立了柔性网增强薄膜材料的拟层单胞力学模型，确定了柔性网增强薄膜材料力学性能的等效性能，评估了增强网格对薄膜材料拉伸力学性能的提升作用，揭示了柔性网格增强薄膜材料阶梯式拉伸失效破坏机理。（5）建立了网格增强圆柱壳结构的整体屈曲力学理论模型,采用瑞利-里兹法确定了能量形式网格增强圆柱壳结构的线性屈曲载荷，通过参数化分析确定了网格材料与结构参数对结构整体屈曲性能的影响规律。建立了网格增强充气梁的弯皱力学模型，确定了网格增强充气梁的起皱载弯矩与失效弯矩，阐明了网格离散化对褶皱扩展的抑制作用。研究成果发表在JMPS、IJSS和IJMS等SCI检索刊物共28篇，会议文章15篇。申请国家发明专利29项，其中16项获得授权。研究结果对理解柔性网增强充气膜结构承载机制以及充气结构轻量化设计具有重要意义。