复合材料圆柱壳屈曲时缺陷敏感度的Koiter理论

本文运用柯依脱理论(Koiter'sTheory)对于复合材料圆柱壳屈曲性能的初始缺陷影响进行了一般性分析,为复合材料壳体的初始缺陷敏感度分析建立了基本控制方程;壳体的初始缺陷被设定为具有某些固定形式的或者是随机形式的,为了讨论和比较各种复合材料叠层壳体的缺陷敏感度的影响,用数值算例计算了由玻璃/环氧,硼/环氧,和炭/环氧等复合材料所组成的圆柱壳体的届曲性能。     

初始缺陷和拉-弯耦合对于叠层板的振动屈曲和非线性动力稳定性的影响

研究了复合材料叠层板的初始缺陷和拉伸-弯曲耦合对于其振动、屈曲和非线性动力稳定性的影响,推导了控制方程,这是一个修正的非线性Mathieu方程,进行了5种典型复合材料的数值计算,它们是玻璃环氧Scotch-1002,芳纶环氧Kevlar-49,硼环氧B4/5505,石墨环氧T300/5208和AS/3501,结果表明,由于初始缺陷以及耦合效应的存在,使叠层板对于进入参数共振更加敏感,并且其振幅大于无初始缺陷或者无耦合效应的叠层板,对于不同材料的复合叠层板,尤其是层数较少的板,耦合效应是不相同的,在板结构的屈曲和动力稳定性设计中,如果忽略了耦合效应的影响,其不安全性将超过10％以上。     

复合材料的强度和稳定性理论中的几个近代问题

本文论述了复合材料的强度和稳定性理论中的三个近代问题:复合材料迭层板的强度准则,多层复合材料圆柱壳的非线性稳定性理论,以及复合材料板的动力稳定性理论。关于迭层板的强度准则,论述了目前以张量多项式形式所表述的唯象性破坏准则,着重讨论和比较了各种近代理论在确定耦合系数方面的特点和差别。提出了近代理论中所存在的困难和发展趋势。在多层复合材料圆柱壳的非线性稳定性理论分析中,主要的问题在于如何研究和考虑那些非线性因素,诸如由材料的剪切模量所引起的物理非线性,横向剪切变形的影响,壳体结构的初始缺陷和几何非线性,以及前屈曲变形和边界支承条件的影响等。本文指出了考虑这些因素的方法以及它们的影响程度。复合材料板的动力屈曲性能研究是一个重要的近代研究方向。本文提出了关于复合材料本身的阻尼系数,纵向和转动惯性力影响,横向剪切效应,迭层板的初始几何缺陷,以及增强纤维的铺设方向等因素对于动力屈曲性能的影响。同时提出了计算这些影响的方法,指出这些因素在复合材料板的动力稳定性分析中有着重要作用。     

圆柱壳体非线性分析关键技术研究

ANSYS是通用的、大型的有限元分析CAE软件,使用ANSYS软件可以求解静态和瞬态非线性问题.本文在分析了圆柱薄壳结构的特点、分类和应用的基础上,对圆柱壳体的稳定性进行了研究,建立了圆柱壳体非线性力学方程.在ANSYS平台下,对典型的圆柱壳体进行了仿真,为进一步深入研究圆柱壳体非线性问题提供了借鉴.     

复合材料叠层板非线性动力稳定性理论的几个基本问题

本文研究了复合材料叠层板在周期性动力谐载荷作用下的非线性动力稳定性理论中的几个基本问题。其内容包括：用Hamilton原理建立一般性基本方程,考虑了大挠度非线性;惯性力的影响;耦合效应影响,横向剪切效应的影响,以及几何初始缺陷困数等。     

用DR法求解计及湿度影响的复合材料叠层扁壳大挠度弯曲问题

动态松驰法(DR法)是求解工程实际非线性问题的一种有效的、简单的方法、本文采用DR法首次对计及湿度影响的复合材料叠层扁壳的非线性弯曲问题进行了分析。     

开口圆柱壳的回传射线矩阵法精确自由振动分析(英文)

目的:开口圆柱壳作为板壳组合结构的组成部分被广泛应用于工程实践中。本文探讨开口圆柱壳结构参数(长度、半径、厚度和夹角等)和边界条件对其振动特性的影响,这对工程结构的减振设计具有重要意义。通过推导开口圆柱壳的解析解及其求解过程,建立加筋开口圆柱壳和板-壳耦合模型振动分析的理论基础。创新点:1.推导行波与驻波结合形式的解析解;2.建立回传射线矩阵法分析开口圆柱壳结构振动的流程;3.分析得到大模态数下开口圆柱壳固有频率随壳厚线性变化;直边简支时,曲边边界条件对固有频率影响不大。方法:1.基于Donnell-Mushtari-Vlasov(DMV)薄壳理论,推导两对边简支的开口圆柱壳行波与驻波结合形式的解析解;2.基于回传射线矩阵法原理,推导出开口圆柱壳的固有频率方程;3.采用黄金分割法求解开口圆柱壳的固有频率方程,得到精确的固有频率;4.分析开口圆柱壳不同结构参数和边界条件对固有频率的影响。结论:1.回传射线矩阵法适用于开口圆柱壳的振动分析且具有很高的精度;2.开口圆柱壳的固有频率随其长度的增加而减小;3.对于绝大部分模态数,开口圆柱壳的固有频率随其半径的增加而减小;4.开口圆柱壳的固有频率随壳厚的增加而增加,当周向模态数n=1和2时,不同壳厚的开口圆柱壳固有频率相差很小,当周向模态数n≥7时,开口圆柱壳的固有频率随壳厚线性变化;5.对于绝大多数模态数,开口圆柱壳的固有频率随夹角的增大而快速减小;6.对于两曲边简支的开口圆柱壳,其固有频率从高到低对应两直边的边界条件为固支、简支和自由;7.对于两直边简支的开口圆柱壳,两曲边的边界条件对其固有频率的影响不大。     

框架-剪力墙结构的非线性抗震分析

为了进一步了解框架-剪力墙结构在地震作用下的动力特性,本文在对框架-剪力墙结构线性抗震分析的基础上,进一步考虑了结构中的非线性理论,强调框架-剪力墙结构的非线性抗震性.本文采用的分析软件是有限元分析软件ANSYS,用软件对框架-剪力墙结构进行非线性的抗震分析,得出了结构在大震作用下结构的变形和内力.分析结果表明,此结构在大震作用下整体稳定性较好,只有局部构件发生塑性变形,不影响结构的安全性.     

壳体热弹塑性问题的有限元求解方法

本文根据厚壳单元的基本理论,设计了壳体热弹塑性问题的有限元分析程序。经验证,该程序在计算各种工况下壳体的应力应变场时具有较高的精度。     

带肋圆柱壳结构的强度分析和过渡段设计研究

带肋圆柱壳结构广泛应用于许多工程实践之中,用有限元分析方法对不同封端的带肋圆柱壳结构进行了研究,结果表明实体模型封端的变化只影响到带肋圆柱壳结构离封端较近处壳体的应力,当封端为平板时,只影响到附近3跨,当封端为半球面时,只影响到附近1跨,其他各跨的等效应力值基本相等,即封端为平扳时的过渡段长度大于封端为半球面时的过渡段长度。建议在进行带肋圆柱壳结构试验时优先选用半球面封端,这样可以使实体模型的长度减少,同样可以获得带肋圆柱壳典型跨的强度数据。     

半解析法求解含轴向浅槽复合材料圆柱壳的非线性动力响应及屈曲问题

The effect of axial shallow groove on the nonlinear dynamic response and buckling of laminated cylindrical shells subjected to radial compression loading was investigated. Based on the first-order shear deformation theory （FSDT）, the nonlinear dynamic equations involving the transverse shear deformation and initial geometric imperfections were derived with the Hamilton philosophy. The axial shallow groove of the laminated composite cylindrical shell was treated as the initial geometric imperfections in the dynamic equations. A semi-analytical method of expanding displacements and loads along the circumferential direction and employing the finite difference method along the axial direction and in the time domain is used to solve the governing equations and obtain the dynamic response of the laminated shell. The B-R criterion was employed to determine the critical loads of dynamic buckling of the shell. The effects of the parameters of the shallow groove on the dynamic response and buckling were discussed in this paper and the results show that the axial shallow grooves greatly affect the dynamic response and buckling.     

Nonlinear Analysis and Optimization of Shallow Shells of Variable Thickness

NomenclaturelintroductionWiththerapiddevelopmelltinshellanalysis,flexibleshellshavefoundWiderapplicationsinengineering.Muchattentionisculal.entlyfoctlsedonthenonlinearbendingandstabilityproblemsofthoseshells.Thebehaviorofflexibleshellsisgovernedbynonlinea…     

The Hamilton System and Hamilton Type Generalized Variational Principle for the Laminated Composite Plates and Shells

lintroductionTileHamilton'systemwasfirstestablishedinthegeometricaloptics,andwasappliedtothetheoreticalmechanicslater.ItsbasicideaistotransformtheEuclidspacetothesymplecticgeometryspaceforcomputing,thatistosay,theLagrangeequationsarechangedintotheHamilton…     

Some Problems in Nonlinear Dynamic Instability and Bifurcation Theory for Engineering Structures

In civil engineering, the nonlinear dynamic instability of structures occurs at a bifurcation point or a limit point. The instability at a bifurcation point can be analyzed with the theory of nonlinear dynamics, and that at a limit point can be discussed with the theory of elastoplasticity. In this paper, the nonlinear dynamic instability of structures was treated with mathematical and mechanical theories. The research methods for the problems of structural nonlinear dynamic stability were discussed first, and then the criterion of stability or instability of structures, the method to obtain the bifurcation point and the limit point, and the formulae of the directions of the branch solutions at a bifurcation point were elucidated. These methods can be applied to the problems of nonlinear dynamic instability of structures such as reticulated shells, space grid structures, and so on.     

工程结构中非线性动态失稳与分叉理论

In civil engineering, the nonlinear dynamic instability of structures occurs at a bifurcation point or a limit point. The instability at a bifurcation point can be analyzed with the theory of nonlinear dynamics, and that at a limit point can be discussed with the theory of elastoplasticity. In this paper, the nonlinear dynamic instability of structures was treated with mathematical and mechanical theories.The research methods for the problems of structural nonlinear dynamic stability were discussed first, and then the criterion of stability or instability of structures, the method to obtain the bifurcation point and the limit point, and the formulae of the directions of the branch solutions at a bifurcation point were elucidated. These methods can be applied to the problems of nonlinear dynamic instability of structures such as reticulated shells, space grid structures, and so on.