安全壳钢衬的初始后屈曲分析

基于Ｄｏｎｎｅｌｌ的非线性板壳理论，认为钢衬壳是一种有特殊缺陷形状的钢衬板，用初始后屈曲渐进分析理论，研究了在温度应力作用下缺陷钢衬板即钢衬壳的初始后屈曲性态。计算了一个四点铆固钢衬壳模型，同时给出了铆钉间距等参数对钢衬壳屈曲极值温度的影响。     

组合壳屈曲和后屈曲分析

讨论组合壳屈曲和后屈曲分析中有关两壳交线上节点广义位移的转移矩陈和刚度矩陈修改等问题，给出具体的转换矩陈，并用它分析计算了断面为Ｌ型，Ｚ型和Ｈ型三种壳体结构。     

冲击后含损伤复合材料格栅加筋板的后屈曲

采用数值分析方法研究了冲击后含损伤的复合材料格栅加筋板的后屈曲特性。基于Mindlin 一阶剪切理论和Von Karman 大挠度理论, 建立了冲击后蒙皮内含分层损伤复合材料格栅加筋板后屈曲分析的有限元方法; 分析中同时考虑了蒙皮和肋骨中纤维断裂、基体开裂等损伤累积造成的刚度的退化和蒙皮分层子板间的闭合接触效应, 为含损伤复合材料格栅加筋板的后屈曲特性研究提供了一种有效的数值分析方法。分析结果表明, 蒙皮分层面积较大时, 格栅加筋板出现蒙皮分层上子板的局部屈曲后仍然具有较强的继续承载能力, 而在后屈曲分析中, 应考虑损伤累积对格栅加筋结构承载能力的影响; 采用非线性虚拟界面元可成功处理分层子板间的闭合接触效应。      

复合材料格栅加筋板的分层扩展特性

采用有限元方法对低速冲击后蒙皮内含有不同分层形式的复合材料格栅加筋(AGS)板的分层扩展行为进行了数值模拟。采用虚裂纹闭合技术计算分层前缘的总能量释放率,并以总能量释放率准则作为分层扩展判据,结合自适应网格移动技术,分别研究了在压缩载荷作用下,蒙皮内具有圆形和椭圆形分层的复合材料格栅加筋板的分层扩展过程。数值研究结果表明:分层深度的变化导致了AGS的分层扩展特性十分复杂,它与分层深度、初始分层尺寸、蒙皮和肋骨的刚度比、后屈曲变形模式等因素都密切相关。本文结论对AGS的承载能力预测及优化设计具有一定的参考价值。     

PUBLICATIONS ON THERMAL STRESSES

The study of the nonlinear response of sandwich flat panels exposed to thermomechanical loading systems is the topic of this article. The sandwich structure considered in this article consists of a thick core layer bonded by the face layers, which are assumed to be symmetrically located with respect to the midplane of the overall structure. The loads involved in this analysis consist of biaxial compressive edge loads, a lateral pressure, and a nonuniform temperature field. The effects of the unavoidable initial geometric imperfections and the character of tangential boundary conditions are incorporated, and their implications upon the structural response are explored. In short, the results of this study are intended to provide pertinent information on the thermomechanical load-carrying capacity of flat sandwich structures.     

Nonlinear mechanical,thermal and thermo-mechanical postbuckling of imperfect eccentrically stiffened thin FGM cylindrical panels on elastic foundations

This paper presents an analytical approach to investigate the nonlinear stability analysis of eccentrically stiffened thin FGM cylindrical panels on elastic foundations subjected to mechanical loads, thermal loads and the combination of these loads. The material properties are assumed to be temperature-dependent and graded in the thickness direction according to a simple power law distribution. Governing equations are derived basing on the classical shell theory incorporating von Karman–Donnell type nonlinearity, initial geometrical imperfection, the Lekhnitsky smeared stiffeners technique and Pasternak type elastic foundations. Explicit relations of load–deflection curves for FGM cylindrical panels are determined by applying stress function and Galerkin method. The effects of material and geometrical properties, imperfection, elastic foundations and stiffeners on the buckling and postbuckling of the FGM panels are discussed in detail. The obtained results are validated by comparing with those in the literature..     

基于改进弧长法的层压复合壳后屈曲反应分析

研究了层压复合壳在横向均匀外压作用下的后屈曲反应。应用全拉格朗日公式描述和9结点退化三维壳单元。提出了一种渐进破坏的模式,并且引入改进的弧长法用于非线性有限元分析。重点研究了不同铺设顺序及方向的层压复合壳后屈曲变形形态和破坏过程。数值计算结果的精度和稳定性得以证实。     

基于三维Puck失效准则及唯象模量退化的复合材料臂杆屈曲分析

针对碳纤维增强树脂基复合材料（CFRP）臂杆结构在压缩和扭转载荷条件下屈曲与后屈曲问题,采用三维Puck失效准则和基于唯象分析的模量退化方法,同时考虑层合结构就位效应及沿纤维方向应力对横向强度的影响,建立了一种适用于考虑渐进失效CFRP结构的屈曲分析方法,并通过编写有限元软件ANSYS的USERMAT子程序进行了数值实现。与文献中实验结果的对比表明,上述方法能够分析复合材料结构的渐进失效过程和后屈曲承载特性,预测精度高。进而采用此方法,详细分析了某航天器臂杆结构在承受压缩与扭转载荷条件下的屈曲载荷及后屈曲特性。      

Free vibration behavior of a thermally post-buckled FG Timoshenko beam under large deflection using a tangent stiffness-based method

For thermally postbuckled configurations, the free vibration behavior of functionally graded (FG) Timoshenko beams are investigated. The postbuckling configurations are obtained through a geometrically nonlinear static problem. The free vibration problem around the postbuckled configuration is formulated using its tangent stiffness. The energy based governing equations are solved following the Ritz method. The elements of the tangent stiffness matrix are obtained using the Ritz coefficients. The results are shown to exhibit the effects of FG material, material profile parameter, and length-thickness ratio. The comparative results are presented for both the cases of the physical neutral surface and the geometrical neutral surface.     

Study on postbuckling of axial compressed elastoplastic functionally graded cylindrical shells

Postbuckling of plates and shells is an important and cumbersome problem in the structural stability field. Presently, postbuckling behaviors of elastoplastic functionally graded cylindrical shells are investigated by a numerical simulation. The elastoplastic material properties are assumed to be of a multilinear hardening type, according to the constituent distributions, and are modeled using the laminate method. The Riks algorithm is used to obtain the equilibrium path. The postbuckling deformation and stain history of elastoplastic functionally graded cylindrical shells are investigated and various effects of the shell thickness and the constituent distributions are discussed. The results show material unloading effects in the postbuckling state.