功能梯度材料圆板的非线性热振动及屈曲

采用弹性理论建立了功能梯度材料板的静力平衡方程,利用静力平衡方程确定了功能梯度材料板的中性面位置,在此基础上推导出了功能梯度材料板在均匀温度场中的非线性振动及屈曲微分方程组,求得了功能梯度材料圆板的非线性振动及屈曲的近似解,讨论分析了中性面位置、梯度指数、温度等因素对功能梯度材料圆板非线性振动及屈曲的影响.把该方法计算结果与有限元计算结果进行了比较,验证了该方法的计算结果是可靠的.算例分析表明,中性面位置对均匀温度场中功能梯度材料圆板的非线性振动及屈曲有一定影响.     

功能梯度材料椭圆板的非线性热振动及屈曲

采用弹性理论建立了功能梯度材料板的静力平衡方程,利用静力平衡方程确定了功能梯度材料板的中性面位置,在此基础上推导出了功能梯度材料板在均匀温度场中的非线性振动及屈曲微分方程组,求得了功能梯度材料椭圆板的非线性振动及屈曲的近似解,讨论分析了中性面位置、梯度指数、温度等因素对功能梯度材料椭圆板非线性振动及屈曲的影响.把该方法计算结果与有限元计算结果进行了比较,验证了该方法的计算结果是可靠的.算例分析表明,中性面位置对均匀温度场中功能梯度材料椭圆板的非线性振动及屈曲有一定影响.     

起重机上翼缘仿生简支板的局部稳定性分析

研究面内荷载作用下起重机上翼缘仿生简支板的局部稳定性分析问题。针对起重机箱梁结构轻量化设计,上翼缘板厚度变薄导致的局部稳定性改进。借鉴与起重机上翼缘板存在相似结构、受力和功能特性的生物叶脉结构,模仿叶脉倾斜、交错等结构特征提出了叶脉斜向肋箱梁结构设计。鉴于斜板屈曲稳定性数值求解的复杂性,给出仿生简支板结构模型分析,给出约束边界条件和加载的具体实现方法。利用有限元软件结合实例分析表明,仿生简支板结构局部稳定性大大提高。简支斜板底边和高度不变时,屈曲临界载荷随倾角增大而减小;斜板底边长和倾角不变时,屈曲临界载荷随高度增大而减小。简支加劲斜板倾角θ=45°较90°时屈曲临界载荷提高较大。     

复合材料加筋板后屈曲快速计算方法研究

为了提高使用材料的稳定性和有效性,针对航空航天飞行器中的典型结构复合材料加筋曲板的屈曲及后屈曲问题,根据等效宽度法的解析表达式,提出了一种快速计算方法,用MATLAB实现了屈曲临界载荷的数值解。改进方法与参考文献试验结论和有限元仿真有很好的一致性。研究了筋条高度变化对扭转刚度、弯曲刚度的影响,以及筋条高度与极限载荷、等效宽度之间的关系,为加筋板的实际工程开发和应用提供了便捷方法。     

加筋短板后屈曲特性分析与试验研究

作为飞机结构的基本元素,加筋短板有较为宽广的非线性后屈曲区间.通常采用工程计算方法作为加筋板的设计依据,未充分利用结构的后屈曲强度.为研究加筋短板的后屈曲特性,求解加筋短板的后屈曲路径以及极限载荷,采用GMNIA(Geometrically and material nonlinear analysis with imperfections)仿真分析方法预测了加筋短板的极限载荷,得到了反映后屈曲路径的载荷—应变曲线,并与试验进行对比分析.研究结果表明,加筋短板初始屈曲发生在蒙皮的自由边,长桁是后屈曲的主要承载部位;有限元仿真的极限载荷与试验破坏载荷的相对误差为0.46％,有限元仿真的后屈曲平衡路径与试验吻合较好.因此,采用GMNIA仿真分析方法能够准确的分析加筋短板的后屈曲特性,达到减轻结构重量、提高结构效率的目的.     

基于ANSYS的天线杆屈曲分析

论文介绍了屈曲分析的定义和屈曲分析有限元分析法,采用有限元分析软件ANSYS建立了天线杆的有限元模型,然后对天线杆进行了线性屈曲分析和非线性屈曲分析,分别求出了屈曲模态及临界载荷,并将分析结果进行对比.对不同的初始缺陷的情况进行屈曲分析,得出临界载荷随初始缺陷的变化规律,分析结果为结构的优化设计提供了理论基础,对类似结构的屈曲分析提供了参考依据.     

基于有限元模型的建筑混凝土柱屈曲承载力计算

为了解决传统混凝土承载力算法存在峰值负荷计算值误差较大的问题,本文提出基于有限元模型的建筑混凝土柱屈曲承载力计算方法.通过有限元模型,对混凝土柱进行有限元数值模拟分析,模拟其屈曲力学性能,判断混凝土柱整体抗屈曲强度,确定屈曲承载力极限时的应力-应变关系曲线,并完成曲线参数计算.此次算法与两种传统算法进行对比实验,对三组混凝土柱试件进行破坏,比较峰值负荷计算值和试验值,结果表明,此次算法减小了峰值负荷的计算误差,此次算法的屈曲承载力计算结果更为准确.     

轴向载荷作用下圆柱壳的屈曲仿真

本文采用非线性有限元方法，在经典刚塑性理论的基础上，考虑了材料非线性、大变形效应对材料的影响，利用大型通用程序LS—DYNA对圆柱壳轴向冲击屈曲过程进行了计算机仿真分析。分析表明，利用非线性有限元数值仿真方法，可以对圆柱壳屈曲这一复杂的力学过程进行真实有效的模拟再现。     

铝合金受压板件局部屈曲承载力设计方法

为考察现有铝合金设计规范预测非焊接受压板件承载力的准确性,采用壳单元建立单向受压四边简支板、方形截面管柱和十字形截面轴压柱有限元模型,使用ANSYS计算得到铝合金板件弹塑性屈曲临界应力和极限承载力。数值计算结果与理论分析结果对比发现：现有板件弹塑性屈曲应力理论能够给出铝合金板件屈曲临界应力的下限值,误差较小。中国规范非加劲板件有效厚度预测公式偏保守,因此给出修正的有效厚度预测公式。修正后的非加劲板件有效厚度公式可以提高板件利用率,增强经济性。     

摇摆防屈曲支撑钢框架抗震性能分析

基于防屈曲支撑钢框架（BRBSF）和摇摆防屈曲支撑钢框架（RBRBSF）拟静力试验，建立BRBSF和RBRBSF的有限元模型，利用OpenSees有限元软件对试验框架中采用的梁端削弱截面（RBS）进行分析，研究RBS对BRBSF和RBRBSF性能影响，并基于有限元模型进一步分析BRB参数对RBRBSF的影响.研究结果表明，梁端设置RBS可减小BRBSF梁柱节点弯矩，实现塑性铰外移，但对RBRBSF梁柱节点弯矩影响较小，BRB参数的改变对RBRBSF屈服荷载和承载能力有一定影响，但对框架柱轴力影响较小.     

Asymmetric buckling of bimodulus thick annular plates

An annular element with Lagrangian polynomials and trigonometric functions as shape functions is developed for asymmetric finite element stability analysis. The annular element is based on the Mindlin plate theory so that the effect of transverse shear deformation is included. Using the asymmetric finite element model, the asymmetric static buckling of bimodulus thick annular plates subjected to a combination of a pure bending stress and compressive normal stress is investigated. The obtained results of non-dimensional critical buckling coefficients are shown to be very accurate when compared with the exact solutions. The effects of various parameters on the buckling coefficients are studied. The bimodulus properties are shown to have significant influences on the buckling coefficients.     

Compressional stability behavior of composite plates with through-the-width and embedded delaminations by using first order shear deformation theory

In this paper, the compressive, i.e. bucking and post-buckling, behavior of composite laminates with through-the-width and embedded delaminations is investigated analytically. The analytical method is based on the first order shear deformation theory (FSDT) and its formulation is developed on the basis of the Rayleigh–Ritz approximation technique. In the case of the multiple delaminations, the contact phenomenon has significant effects on the compressional behavior of the laminates. Thus, the contact between the delaminated sublaminates is also considered in the presented FSDT analytical method. The method can handle both local buckling of the delaminated sublaminates and global buckling of the whole plate. Also, the three-dimensional finite element analysis is performed by using ANSYS5.4 general purpose commercial software, and the results are compared with those obtained by the analytical model. The agreement between the results is very good.     

Application of a refined plate bending element to buckling problems

The buckling stiffness matrix of a refined plate bending element is derived for various continuous and non-uniform distributions of in-plane forces. Elements of this matrix are expressed in an explicit form and can, therefore, be readily used in a finite element computer program for solving plate buckling problems with various loading and edge conditions. A number of problems are solved and the results obtained are compared with analytical and/or numerical results obtained by using other procedures. It is shown that the refined plate bending element is superior to simpler elements when used for solving plate buckling problems.     

Axisymmetric buckling of bimodulus thick circular plates

The static buckling of bimodulus thick circular and annular plates subjected to a combination of a pure bending stress and compressive stress is investigated. The thick finite element model, which includes the effect of transverse shear deformation, are created for axisymmetric buckling problems. The obtained results of buckling coefficient are compared with the exact solutions for ordinary thin plates. The accuracy of the finite element solutions are shown to be very good. The effects of various parameters on the buckling coefficients and neutral surfce locations are studied. The bimodulus properties are shown to have significant influences on the buckling coefficient.     

基于ANSYS的角钢局部屈曲/后屈曲等效分析

将角钢等效成简单板材,通过分析其屈曲／后屈曲来等效研究角钢的局部屈曲／后屈曲．采用ANSYS严格按照角型材实际尺寸建立三维实体模型,并进行屈曲／后屈曲数值模拟．三维有限元解与理论等效结果符合良好,充分说明该等效分析的正确性和适用性．     

Elastic buckling of rectangular mindlin plate with mixed boundary conditions

An approximate method for analyzing the elastic buckling of Mindlin plates is proposed. The solutions of the differential equations of buckling of Mindlin plate are obtained in discrete forms by applying numerical integration. The discrete solutions give the transverse shear forces, twisting moment, bending moments, rotations and deflection at the all discrete points which are the intersections of the vertical and horizontal equally dividing lines on the plate. In order to confirm the convergency and accuracy of numerical solutions, the buckling loads of simply supported square Mindlin plates are calculated, and the results are compared with other published finite element solutions. As an application, the buckling loads and buckling modes of Mindlin plates with various types of mixed boundaries are calculated.     

Probabilistic buckling analysis of fiber metal laminates under shear loading condition

The design allowables for compressive and shear buckling of fiber metal laminate (FML) panels need to be developed for the certification of these materials. In this paper, the shear buckling behavior of the two FML panels, ARALL3-3/2 and GLARE3-2/1, is investigated using a probabilistic analysis method in order to predict the distributions of the buckling load. The scatter associated with the material properties and the randomness in the loading conditions are accounted for in the probabilistic analysis. The shear buckling load of the panel is taken as the response function of the material properties and the load parameter. The response surface methodology (RSM) is employed for the development of the response function based on limited finite element data. Three RSM design methods: full factorial design, CCD design and saturated D-optimum design, are applied to construct the response function following which the shear buckling load distributions of the two FML panels are predicted. The predicted results are verified using independently generated finite element data.     

Critical buckling of delaminated composite plates using exact stiffness analysis

The critical buckling of composite plates with through-the-length delaminations is studied using exact stiffness analysis and the Wittrick–Williams algorithm. Computational efficiency is achieved by avoiding discretisation into elements, making the method suitable for preliminary aircraft design. Numerical results for longitudinal, transverse and shear loading show a transition from global to local buckling modes as the delamination width is increased. The critical buckling strength is dramatically reduced as the delamination is moved towards the plate surface, but is relatively insensitive to its widthwise location or to the edge conditions. The results are compared with finite element analysis.