用于AGS结构分析的混合法

结合均匀化模型和加筋单元模型构造了一种混合模型用来分析复合材料格栅加筋板/壳结构（AGS）。所构造的加筋单元模型是一种高性能协调转角独立加筋板壳单元,保持了肋骨和蒙皮位移场的协调性,同时还满足肋骨和蒙皮具有独立转动条件,该单元中肋骨的方向和位置任意。混合法具有精度高、速度快等特点。通过典型算例讨论了肋骨间距和高度对均匀化模型计算结果精度的影响,通过对带孔复合材料AGS板孔边特殊点应力值的分析证明了混合法的有效性。      

复合材料旋转壳轴对称问题的几何非线性分析

本文以文［１］为基础,提出了一种修正的二维曲壳等参元,并用之分析了承受轴对称荷载的层会复合材料旋转天的几何非线性问题。数值算例表明：该单元精度较高,对多层复合材料厚薄壳均是有效的。     

板锥网壳结构的静力有限元分析

板锥网壳结构是一种受力性能合理,技术经济效益良好的新型空间结构形式。本文采用组合结构有限元法对板锥网壳结构进行了线弹性静力分析,分别考虑了三种计算力学模型,着重研究了具有内节点的三角形板单元及复合材料层合板单元,编制了板锥网壳结构的专用计算程序。     

复合材料大变形任意加筋壳单元

构造了用于复合材料偏心加筋壳形结构大变形分析的任意加筋壳单元。在此模型中,肋骨连同壳的整体被视为一个单元偏心加筋壳单元。肋骨可放在壳单元内的任意位置和任意方向。所构造单元的特点是在网格划分时,可不必考虑肋骨的位置,这就给网格划分带来了很大的灵活性。在壳和肋骨的方程中,引用Von-Karman大变形理论计及几何非线性的影响,按照Mindlin-Reissner一阶剪切变形理论考虑横向剪切变形。     

复合材料偏心加筋壳特性分析

用任意加筋壳单元研究了复合材料偏心加筋壳结构的特性．研究表明，在结构几何尺寸已经确定的情况下，可以调整加强肋骨的偏心量，以改变加筋壳结构内部的受力和变形；调整加强肋骨的布置方式也是改变加筋壳结构强度和刚度的有效方法．     

旋转周期复合材料层合结构的有限元屈曲分析

针对空间结构中常见的复合材料层合壳体结构发展了一种多层相对自由度层合壳元。这种实体型壳元既可以用较粗的网格很好地模拟层合壳, 又易与三维实体单元相连接, 使变厚度、带有补强的复合材料层合壳体等复杂结构得以正确建模。同时运用旋转周期有限元技术对大规模的空间复合材料层合结构成功实施了屈曲分析。数值算例验证了本文计算策略的有效性。      

复合材料层合板壳热弹性动力响应

本文提出了一个复合材料层合扁壳的位移场。据此导出了在力载和热载作用下的板壳运动方程。该位移场满足层间位移和横向剪应力的连续性,较充分反映了横向剪切对层合板壳力学行为的影响,但位移场的变量和运动方程均为五个,与一阶剪切变形理论相同。文中以暂态响应为例考察了横向剪切变形对层合板壳动力响应的影响,显着改善了解的精度。      

复合材料多层圆柱壳振动和声辐射问题研究进展

鉴于复合材料优良的力学和声学性能，将其用于潜艇结构已成为未来的发展趋势和研究重点。而圆柱壳作为潜艇的主体结构形式，针对复合材料多层圆柱壳的振动和声辐射问题的研究已广泛开展。在满足水下承载能力的前提下，复合材料耐压圆柱壳趋于中厚壳，甚至厚壳，沿壳体厚度方向的横向剪切变形、压缩变形、截面翘曲变形不可忽略，这些因素直接决定了横向振动位移场描述的准确度，会进一步影响壳体周围声辐射场预报的准确性。现有的壳体理论主要有经典壳体理论、一阶剪切变形理论、高阶剪切变形理论、分层理论、锯齿理论和三维弹性理论等，这些理论发展比较成熟，但大多研究仍局限于正交各向异性薄壳结构的振动问题，涉及各向异性材料厚壳结构的声辐射研究较少，且目前对于这些壳体理论在复合材料圆柱壳的振动和声辐射问题的适用性方面缺乏系统的总结和研究。本文首先从复合材料的刚度特性出发说明其振动和声辐射问题求解的复杂性，然后从横向振动位移场的角度综述了这些理论的发展过程、研究现状以及各自的特点，最后给出了这些理论的适用范围和使用建议，并提出了有待进一步研究的问题，以期为复合材料多层圆柱壳结构的设计和振声性能分析提供参考。     

基于ANSYS的复合材料螺旋桨叶片有限元建模与分析

针对船用复合材料螺旋桨叶片,分别采用壳单元赋予不同截面参数和实体单元赋予不同等效材料参数两种建模方法进行了有限元分析,对比了壳单元和实体单元模型的模态、均布压力载荷下的响应以及均匀温度场中的热变形。结果表明:对于从桨根到桨尖各位置铺层不同的叶片来说,两种建模方法在建模时间和铺层调整便捷性方面各有利弊;模态分析中两种模型的固有频率和振型计算结果存在一定差异,它们均可在一定条件下用于复合材料螺旋桨叶片模态计算;两种模型中,模拟均布压力载荷下的响应时应采用壳单元模型,而分析叶片在均匀温度场中结构的热变形应采用实体单元模型。     

几何非线性复合材料层合固体壳单元

通过定义广义应力,提出了一个改进的刚度矩阵,以克服固体壳元的厚度自锁问题,并能保证沿复合材料层合结构厚度方向上的连续应力分布;将应力插值函数分为低阶和高阶两部分,建议了一个新的非线性变分泛函,推导了一个用于几何非线性分析的九节点固体壳单元,该单元的计算精度和效率基本上与九节点减缩积分单元相当,与同类型其他单元相比,该单元显著提高了计算效率。     

Analysis for buckling and vibrations of composite stiffened shells and plates

This paper deals with development of triangular finite element for buckling and vibration analysis of laminated composite stiffened shells. For the laminated shell, an equivalent layer shell theory is employed. The first-order shear deformation theory including extension of the normal line is used. In order to take into account a non-homogeneous distribution of the transverse shear stresses a correction of transverse shear stiffness is employed. Based on the equivalent layer theory with six degrees of freedom (three displacements and three rotations), a finite element that ensures C⁰ continuity of the displacement and rotation fields across inter-element boundaries has been developed. Numerical examples are presented to show the accuracy and convergence characteristics of the element. Results of vibration and buckling analysis of stiffened plates and shells are discussed.     

A Continuum Based Thick Shell Element for Large Deformation Analysis of Layered Composites

A new continuum based thick shell model is presented for modeling orthotropic laminated shell structures undergoing large elastic deformations. An equivalent single-layer model involving seven nodal degrees of freedom is used. In that layered model, there are no restrictions on the number of layers, their thickness and their stacking sequence. The shell model accounts explicitly for the thickness change in the shell, as well as the normal stress and strain states through its thickness. Shear locking is avoided using an assumed natural strain formulation, while thickness locking is avoided using modified displacement interpolation functions. The performance of the layered shell element is tested using several linear and non-linear composite plate and shell problems involving anisotropic, angle and cross-ply laminates, cylindrical and spherical shells.     

用双B样条函数法分析扁壳结构内力

本文提出了用双B样条函数作为双曲扁壳位移场插值函数,从而对双曲扁壳结构静力与动力问题进行了系统研究,推导出分析该问题的有关求解公式。本文方法适用于双曲扁壳结构在各种外荷载作用、各种边界条件下的应力场、位移场及自振频率分析。     

板壳分析与应用

板壳分析是现代固体力学的一个重要分支。这门学科几乎与一切工程设计都有关联,对航天、航空、航海、机械、石化、建筑、水利、动力、仪表、交通等工程设计,尤其具有指导意义。现今,经典的薄板壳线性 理论已较成熟,并在各种工程设计中起着指导作用。然而,在薄板壳非线性领域和厚板壳线性领域,还有许多问题未被解决。章在介绍这门学科发展历史的基础上,概述了作近四十年结合工程实际对波纹板壳、单层板壳、双层金属旋转扁壳、网格扁壳、夹层板壳和复合材料层合板壳等六类薄板壳的非线性弯曲、稳定和振动问题以及厚、薄板壳弯曲问题进行理论探索的情况。     

A four‐noded quadrilateral element for composite laminated plates/shells using the refined zigzag theory

A new bilinear four‐noded quadrilateral element (called quadrilateral linear refined zigzag) for the analysis of composite laminated and sandwich plates/shells based on the refined zigzag theory is presented. The element has seven kinematic variables per node. Shear locking is avoided by introducing an assumed linear shear strain field. The performance of the element is studied in several examples where the reference solution is the 3D finite element analysis using 20‐noded hexahedral elements. Copyright © 2013 John Wiley & Sons, Ltd.     

Free and forced vibration analysis of laminated composite plates and shells using a 9-node assumed strain shell element

The natural frequencies of isotropic and composite laminates are presented. The forced vibration analysis of laminated composite plates and shells subjected to arbitrary loading is investigated. In order to overcome membrane and shear locking phenomena, the assumed natural strain method is used. To develop a laminated shell element for free and forced vibration analysis, the equivalent constitutive equation that makes the computation of composite structures efficient was applied. The Mindlin-Reissner theory which allows the shear deformation and rotary inertia effect to be considered is adopted for development of nine-node assumed strain shell element. The present shell element offers significant advantages since it consistently uses the natural co-ordinate system. Results of the present theory show good agreement with the 3-D elasticity and analytical solutions. In addition the effect of damping is investigated on the forced vibration analysis of laminated composite plates and shells.     

Smart damping of geometrically nonlinear vibrations of composite shells using fractional order derivative viscoelastic constitutive relations

In this article, a three-dimensional fractional order derivative model has been developed for the constrained viscoelastic layer of the active constrained layer damping (ACLD) treatment of laminated composite shells undergoing geometrically nonlinear vibrations. The constraining layer of the ACLD treatment is made of vertically/obliquely reinforced 1–3 piezoelectric composites and acts as the distributed actuator. A three-dimensional smart nonlinear finite element model has been developed. Several numerical results are presented to check the accuracy of the present three-dimensional fractional derivative model of the constrained viscoelastic layer for smart damping of geometrically nonlinear vibrations of laminated composite shells.     

A co-rotational 8-node assumed strain shell element for postbuckling analysis of laminated composite plates and shells

 The formulation of a nonlinear composite shell element is presented for the solution of stability problems of composite plates and shells. The formulation of the geometrical stiffness presented here is exactly defined on the midsurface and is efficient for analyzing stability problems of thin and thick laminated plates and shells by incorporating bending moment and transverse shear resultant forces. The composite element is free of both membrane and shear locking behaviour by using the assumed natural strain method such that the element performs very well as thin shells. The transverse shear stiffness is defined by an equilibrium approach instead of using the shear correction factor. The proposed formulation is computationally efficient and the test results showed good agreement. In addition the effect of the viscoelastic material is investigated on the postbuckling behaviour of laminated composite shells. Received: 6 February 2002 / Accecpted: 6 January 2003 ID=" Present address: School of Civil Engineering, Asian Institute of Technology     

Static and Dynamic Analysis of Laminated Thick and Thin Plates and Shells by a Very Simple Displacement-based 3-D Hexahedral Element with Over-Integration

A very simple displacement-based hexahedral 32-node element (denoted as DPH32), with over-integration in the thickness direction, is developed in this paper for static and dynamic analyses of laminated composite plates and shells. In contrast to higher-order or layer-wise higher-order plate and shell theories which are widely popularized in the current literature, the proposed method does not develop specific theories of plates and shells with postulated kinematic assumptions, but simply uses the theory of 3-D solid mechanics and the widely-available solid elements. Over-integration is used to evaluate the element stiffness matrices of laminated structures with an arbitrary number of laminae, while only one element is used in the thickness direction without increasing the number of degrees of freedom. A stress-recovery approach is used to compute the distribution of transverse stresses by considering the equations of 3D elasticity. Comprehensive numerical results are presented for static, free vibration, and transient analyses of different laminated plates and shells, which agree well with existing solutions in the published literature, or solutions of very-expensive 3D models by commercial FEM codes. It is clearly shown that the proposed methodology can accurately and efficiently predict the structural and dynamical behavior of laminated composite plates and shells in a very simple and cost-effective manner.