复合材料层合开顶扁球壳在集中冲击下的非线性动力屈曲

研究了具有刚性中心的复合材料层合开顶扁球壳在中心集中冲击载荷作用下的非线性动力屈曲问题。通过增加横向转动惯量项得到中心集中冲击下复合材料层合开顶扁球壳非线性稳定性的控制方程，采用Galerkin方法得到以刚性中心位移表达的冲击动力响应方程，并用Runge-Kutta方法进行数值求解，应用Budiansky-Roth准则（简称B—R准则）确定冲击屈曲的临界荷载；讨论了壳体几何尺寸对复合材料层合开顶扁球壳冲击屈曲的影响。     

复合材料层合扁锥壳的冲击屈曲

研究了计及横向剪切的对称铺设正交异性复合材料层合扁锥壳在三角脉冲载荷作用下的非线性动力屈曲问题；通过在复合材料层合扁锥壳非线性稳定性的基本方程中增加横向转动惯量项并引入三角脉冲冲击力，得到了层合扁锥壳的冲击控制方程，采用Galerkin方法得到以顶点挠度表达的冲击响应方程，并用Runge—Kutta方法进行数值求解，应用B—R准则确定冲击屈曲的临界荷载；讨论了壳体几何参数、物理参数和边界条件对复合材料层合扁锥壳冲击屈曲的影响。     

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。      

考虑接触效应的具轴对称脱层层合圆柱壳的非线性动力响应分析

基于非线性弹性壳理论,建立了考虑脱层接触效应的具轴对称脱层层合圆柱壳的运动控制方程。引入假想弹簧计算接触力,然后对系统的横向运动控制方程进行修正,从而有效地避免了脱层之间的相互贯穿。整个问题采用有限差分法进行求解,算例中,详细讨论了脱层的大小、深度、位置以及载荷等因素对具脱层轴对称层合圆柱壳非线性动力响应的影响。数值计算结果表明,在脱层结构动力响应分析中考虑接触效应是非常重要的,它可避免脱层结构出现物理上不可能的相互贯穿。     

低速冲击下含损伤层合中厚浅球壳的非线性动力响应分析

基于中厚壳几何非线性理论和损伤理论 , 采用应变描述的失效准则 , 导出了层合浅球壳含基体损伤和纤维2基体剪切损伤的损伤本构关系 , 建立了低速冲击下轴对称正交对称铺设层合中厚浅球壳的非线性运动控制方程。对未知函数在空间域采用正交配置法离散 , 时间域采用 Newmark2 β方法离散 , 对整个问题进行迭代求解。数值结果表明 , 损伤、 冲击物的初速度以及结构的几何参数都在不同程度上影响着低速冲击下结构所受的冲击载荷和结构的非线性动力响应。      

层合中厚浅球壳受撞击时的非线性动力响应分析

建立了正交铺设层合中厚浅球壳在任一位置受撞击载荷作用的非线性运动微分方程,根据Hertzian定律,考虑撞击物与浅球壳之间的弹性接触效应,确定了壳体在其接触处所承受的冲击力。对此非线性动力问题,采用有限差分法与时间增量法求解。算例中,讨论了撞击物的速度、壳体中曲面曲率半径及接触点位置对壳体所受冲击载荷及其位移响应的影响。     

冲击波作用下土中浅埋扁球壳的非线性动力响应

本文应用一维波阻法分析了土与结构的相互作用,引用法向位移ω及应力函数φ表达了扁球亮非线性轴对称变形的运动方程,将这两个基本未知函数用正交配点法及平均加速度法分别在空间与时域上离散,求得了在冲击波作用下土中浅埋周边弹性支承扁球壳的非线性动力响应,数值计算着重考察了壳的几何参数及非线性因素对动力响应的影响。     

爆炸冲击载荷作用下夹层开顶扁球壳的非线性动力稳定性分析

该文对爆炸冲击作用下夹层开顶扁球壳的非线性轴对称动力稳定性问题进行研究.基于Reissner假设和Hamilton原理,得到了夹层开顶扁球壳在冲击载荷作用下的非线性动力控制方程;采用Galerkin方法对非线性动力控制方程进行求解,得到以刚性中心位移表达的非线性动力响应方程,并应用Runge-Kutta方法进行数值求解...     

粘弹性圆柱壳在轴向恒压下的动力稳定性

基于Timoshenko-Mindlin假设,得到考虑粘弹性的各向同性圆柱壳及纤维增强正交铺设层合圆柱壳在轴向恒压下的动力学方程。文中对两端简支的圆柱壳进行了分析,依Laplace变换,导出动力稳定的特征方程,由Routh-Hurwitz判据建立动力稳定性条件,对两类圆柱壳讨论了横向剪切变形的影响。     

纤维增强复合材料迭层圆柱壳的几何非线性分析

本文从非线性弹性理论出发,在小应变、中等小转动的前提下,全面考虑了变形对于平衡方程的影响,导出了和传统理论不同的壳体非线性理论;并用摄动法和伽略金法分别求解了四边不可动固支正交各向异性复合材料迭层园桂壳块以及考虑横向剪切的四边可动简支园桂形扁壳的非线性弯曲问题。计算表明:变形较大时,变形对所有平衡方程的影响都是值得注意的。      

考虑横向剪切效应时圆柱型正交各向异性球面扁壳在横向载荷作用下的非线性压屈

本文应用参考文献所介绍的修正迭代法探讨了横向载荷作用下,圆柱型正交各向异性圆底球面扁壳的非线性稳定同题,得出了这一同题的解析解。在求解过程中,本文放弃了经典板壳理论的Kirchhoff假定,从而考虑了横向剪应变对于弯曲变形的影响, 计算结果表明:本文的分析方法和结论是正确的;对于正交各向异性复合材料板壳而言,横向剪切效应是值得注意的。     

Thermomechanical postbuckling of multilayered composite panels with cutouts

The results of a study of the detailed thermomechanical postbuckling response characteristics of flat unstiffened composite panels with central circular cutouts are presented. The panels are subjected to combined temperature changes and applied edge loading (or edge displacements). The analysis is based on a first-order shear deformation plate theory. A mixed formulation is used with the fundamental unknowns consisting of the generalized displacements and the stress resultants of the plate. The postbuckling displacements, transverse shear stresses, transverse shear strain energy density, and their sensitivity coefficients are evaluated. The sensitivity coefficients measure the sensitivity of the post-buckling response to variations in the different lamination and material parameters of the panel. Numerical results are presented showing the effects of the variations in the hole diameter, laminate stacking sequence, fiber orientation, and aspect ratio of the panel on the thermomechanical postbuckling response and its sensitivity to changes in panel parameters.     

Vibration and Buckling of Truss Core Sandwich Plates on An Elastic Foundation Subjected to Biaxial In-plane Loads

Truss-core sandwich plates are thin-walled structures comprising a truss core and two thin flat sheets. Since no direct analytical solution for the dynamic response of such structures exists, the complex three dimensional (3D) systems are idealized as equivalent 2D homogeneous continuous plates. The macroscopic effective bending and transverse shear stiffness are derived. Two representative core topologies are considered: pyramidal truss core and tetrahedral truss core. The first order shear deformation theory is used to study the flexural vibration of a simply supported sandwich plate. The buckling of the truss core plate on an elastic foundation subjected to biaxial in-plane compressive loads is also investigated. It's found that the lowest buckling loads and modes are dependent on the foundation stiffness as well as bending and transverse shear stiffness of the plate. The geometric parameters of a sandwich plate are optimized to obtain strongest buckling resistance per unit weight. To verify the accuracy of analytical solutions, 3D finite element (FE) models are established, and good agreement is observed between them. It's obvious that the homogenization procedure leads to great savings in computational effort.     

刚塑性扁球壳受弹体冲击时动力学响应的近似解

研究扁球壳在弹体局部冲击载荷作用下的响应问题.首先,在球壳材料为刚塑性模型的假设下,基于现有球壳理论的研究基础,对球壳的变形能模型进行改进,仅考虑凹陷区域变形能和棱区膜变形能,根据能量守恒原理,得到了球壳在冲击载荷下的理论结果;其次,在棱区的宽度和凹陷区半径之间引入近似关系式l≈0.05a,以此为基础给出了刚塑性球壳在低速弹体冲击下的显式近似理论解;进一步,将近似解与实验的各种情况进行对比,误差均小于10%;最后,采用LS-DYNA 有限元软件进行数值模拟,也取得了与近似解一致的结果.     

A further discussion of nonlinear mechanical behavior for FGM beams under in-plane thermal loading

Due to the variation in material properties through the thickness, bifurcation buckling cannot generally occur for plates or beams made of functionally graded materials (FGM) with simply supported edges. Further investigation in this paper indicates that FGM beams subjected to an in-plane thermal loading do exhibit some unique and interesting characteristics in both static and dynamic behaviors, particularly when effects of transverse shear deformation and the temperature-dependent material properties are simultaneously taken into account. In the analysis, based on the nonlinear first-order shear deformation beam theory (FBT) and the physical neutral surface concept, governing equations for both the static behavior and the dynamic response of FGM beams subjected to uniform in-plane thermal loading are derived. Then, a shooting method is employed to numerically solve the resulting equations. The material properties of the beams are assumed to be graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents, and to be temperature-dependent. The effects of material constants, transverse shear deformation, temperature-dependent material properties, in-plane loading and boundary conditions on the nonlinear behavior of FGM beams are discussed in detail.     

复合材料迭层板柱状弯曲的非线性流固耦合动力响应分析

导出置于液面上的复合材料迭层板变形时流体作用力的近似表达式; 由Ham ilton 原理建立了考虑横向剪切变形以及流固耦合效应时迭层板的非线性动力方程; 采用差分方法求解了迭层板的非线性流固耦合动力响应; 讨论了不同载荷类型下流场深度及几何非线性对动力响应的影响。      

板式橡胶支座梁桥的典型横向震害及其影响因素分析

针对板式橡胶支座梁桥在汶川地震中大面积失效的现象,基于震害调查资料对这类桥梁的典型横向震害特征进行了总结,然后基于试验成果和理论分析模型,采用增量动力分析研究了典型桥例的地震损伤过程,并与震害特征进行对比验证,采用参数分析揭示了桥梁横向震害特征的关键影响因素及其规律。研究表明:板式橡胶支座梁桥的典型横向震害是位移失控,其结构性损伤很轻;支座的柔性和滑移对墩柱抗震有利,但当地震动较大时,挡块脆断会造成梁体严重移位、支座脱空;挡块的强度、变形能力、间隙和支座的摩擦因数都是横向震害的影响因素;强度和变形能力越大,挡块限位效果越好,但强度增大会造成墩柱延性系数成倍增长,而变形增大对墩柱的影响明显更小;间隙是保证支座隔震和挡块限位的重要方面,不宜过大也不宜过小,该研究中桥例取5 cm时可达最优效果;摩擦因数对支座隔震效果的影响很大,摩擦因数越大,墩柱的延性系数也越高;改善挡块变形可达到与提高强度相同的限位效果,且对支座隔震的阻碍更小。因此,对传统挡块进行改进宜从提高其变形的角度出发,工程应用中可综合优化挡块的强度和变形来实现预期抗震目标。     

Transverse shear modulus and strength of honeycomb cores

The transverse shear mechanical behavior and failure mechanism of aluminum alloy honeycomb cores are investigated by the single block shear test in this paper. The transverse shear deformation process of honeycomb cores may be approximately categorized into four stages, namely elastic deformation, plastic deformation, fracture of cell walls and debonding of honeycomb cores/facesheets. The elastic deformation of unit cell under transverse shear displacement is also investigated by the finite element method, and the result shows that the bending deformation of the cell walls is similar to that of the cantilever beam. In order to precisely predict the equivalent transverse shear modulus and strength, not only shear deformation but also bending deformation of cell walls should be considered. Therefore, in the present paper, the equivalent transverse shear modulus and strength are predicted by application of the cantilever beam theory and thin plate shear buckling theory in conjunction with simplifying assumption as to the displacement in the cores. It is concluded that the contribution of bending deformation of cell walls to equivalent transverse shear modulus and strength is obvious with the decreasing height of cell walls.     

打桩过程中桩的横向振动分析

利用Winkler地基土模型对锤击法沉桩时层状地基中预制桩建立了合理的力学模型。经过动力分析,给出了单桩在桩顶偏心动力竖向荷载作用下动力响应的数值解,并分析了激振强度、桩径、土对桩的水平地基反力系数以及土的粘滞阻尼系数等对桩动力响应的影响。为研究桩在强烈轴向和弯矩激振共同作用下的响应提供了初步的分析方法,特别对预制钢筋混凝土桩的设计和施工具有指导意义。