Stability of Plates Made of a Granular Composite with Damageable Components

The stability problem is solved for a plate made of a granular composite material with microdamageable components. Microdamages are simulated by randomly dispersed pores filled with a damaged material. The problem is formulated using the concept of continuous load     

Stability of Plates Made of Fibrous Composite with Damageable Components

The bifurcation stability problem for rectangular plates made of fibrous composite with damageable matrix is formulated and solved__________Translated from Prikladnaya Mekhanika,Vol. 41, No. 5, pp. 83–90, May 2005.     

Stability of Cylindrical Shells Made of Fibrous Composite with Damageable Matrix

The bifurcation stability problem for cylindrical shells made of fibrous composite with damageable matrix is formulated and solved __________ Translated from Prikladnaya Mekhanika, Vol. 41, No. 6, pp. 105–112, June 2005.     

Stability of Shells of Revolution Made of Fibrous Composite with Damageable Matrix

The bifurcation-stability problem for shells of revolution made of fibrous composite with damageable matrix is formulated and solved. Increase in the damage of the matrix under loading is taken into account __________ Translated from Prikladnaya Mekhanika, Vol. 41, No. 10, pp. 75–83, October 2005.     

复合多层混合结构三维热传导分析

复合多层混合结构由不同热导率材料混杂组成。对于分析复合多层混合结构内部热传导机理以及非均匀温度场的复合混合结构热力耦合计算,常需要采用三维模型以得到较为精确的结构温度场分布结果。针对包含复合材料的多层混合结构的热传导问题,本文通过基于散度表示的一般瞬态三维热传导方程,利用Galikin法建立了复合多层混合结构瞬态三维热传导的有限元方程。对于复合多层混合结构单层材料过薄,引起的沿厚度方向划分单元的困难,采用等效三维单元使一个单元内包含一个或数个材料铺层,并在沿厚度方向热导率变化剧烈的情况对单元进行细化。数值仿真结果表明该方法网格划分灵活,计算结果较为理想,同时由于其拓扑结构包含的信息较为充分,能够实现多物理场条件下的耦合分析。     

Natural Vibrations of a Composite Plate Strip with Macrocracks

The fundamental frequency of a clamped composite plate strip with either one free macrocrack or two parallel free cracks is determined using the exact equations of the theory of elasticity. The plate is assumed made of an anisotropic orthotropic material with effective mechanical properties. The problem is solved by the finite-element method. Numerical examples are given to demonstrate how the problem parameters influence the fundamental frequency.     

Stability Analysis of a Vertical Curved Channel Flow with a Radial Temperature Gradient

The linear stability analysis of a Newtonian incompressible fluid in a vertical curved channel formed by two coaxial cylindrical surfaces with a radial temperature gradient and an azimuthal pressure gradient shows that critical modes are oscillatory and non-axisymmetric. We have derived a generalized Rayleigh discriminant which includes both the curvature and buoyancy effects. Centrifugal buoyancy induces weak asymmetry of the dependence of the control parameter critical values on the sign of the temperature gradient. The critical parameters depend on the temperature gradient, the radius ratio and the nature of the fluid. For a wide curvature channel flow, there are two critical modes: oscillatory Dean modes for small temperature gradients and oscillatory centrifugal-thermal modes for relatively large temperature gradients. Received 14 November 2001 and accepted 29 March 2002 Published online: 2 October 2002 Communicated by H.J.S. Fernando     

以新型空壳颗粒复合材料为分配层的成层防护结构抗爆性能试验研究

以成层式人防工程为试验研究背景,分别采用黄沙和新型空壳颗粒复合材料做分配层,开展大比尺集团装药化爆模拟试验,考察其衰减爆炸冲击波的能力。试验结果表明,采用颗粒复合材料构建的分配层,在相同装药量下,遮弹层的变形和破坏明显大于黄沙分配层,应力波上升沿加大,波形脉宽增加,平均峰值应力大概是黄沙分配层的0.65左右,除装药正下方的个别颗粒遭受粉碎性破坏外,绝大部分空壳颗粒依然完好,只是表层泡沫陶瓷略有破损。这说明新型空壳颗粒复合材料不但对爆炸波有非常明显的衰减弥散作用,而且具备承受多次打击的能力。用这种材料做分配层,可大幅提高地下人防工程的抗爆能力。     

带柔性隔板弯曲连续箱梁有限条法分析

本文利用凝聚矩阵求隔板与箱联结点赘余力,进而分析带柔性隔板的曲线连续箱梁及其隔板的内力,并对刚、柔性隔板与无隔板多跨曲箱梁以及直条法与曲条法进行分析比较,表明本文计算结果是令人满意的,从中得到有关结论。     

Stress Distribution in a Rigidly Clamped Composite Plate with Locally Curved Structures under Forced Vibration

A problem on the forced vibrations of a rectangular composite plate with locally curved structures is formulated using the exact three-dimensional equations of continuum mechanics and continuum theory. A technique for numerical solution of the problem is developed based on the semianalytic finite-element method. Numerical results are given for the stress distribution in the plate under forced vibrations. The results obtained are analyzed to study the effect of the curvature in the structure of the plate on the distribution of stress amplitudes. It is shown that the curvatures change significantly the stress pattern under either static or dynamic loading     

薄壁曲梁的稳定性研究进展

曲梁是桥梁、建筑、船舶、航空和航天工程中常见的薄壁构件,根据外载荷与主曲率平面的关系,又被称为拱或水平曲梁.随着工程材料的日益发展,如复合材料、功能梯度材料的引入,曲梁的应用范围更加广泛,进一步推进了薄壁曲梁稳定性问题的研究.本文首先对薄壁梁结构的稳定性行为进行了分类.接着简述了薄壁构件的基本假设,对比了近几十年来薄壁曲梁的基本理论,针对复合材料薄壁曲梁,总结了相应的本构关系,并对各理论间存在的分歧进行了归纳.结合最新的薄壁曲梁研究,根据平衡法、能量法和虚位移(虚功)原理推导出控制微分方程,阐述了相应的求解方法,如解析法、半解析法和数值解法.为验证薄壁曲梁理论的准确性,曲梁承载能力试验验证尤为重要,但目前国内外相关研究还很少,亟待发展.最后讨论了现阶段薄壁曲梁研究的局限性和未来发展的方向.     

Stability of Cylindrical Shells Made of Fibrous Composites with One Symmetry Plane

Cylindrical shells produced by single-layer or cross winding are analyzed for stability. An approximate analytical solution is proposed. It allows evaluating the effect of an unbalanced laminate on the critical values of the axial load, intensity of external pressure, and shear forces. It is shown that the effect of imbalance weakens with increase in the number of laminas. In each specific case, the number of laminas at which the material can be considered orthotropic is determined __________ Translated from Prikladnaya Mekhanika, Vol. 41, No. 6, pp. 113–120, June 2005.     

双轴对称截面薄壁圆弧曲梁的弹性稳定平衡方程

基于薄壁构件分析的基本假定,采用双轴对称截面薄壁圆弧曲梁的精确翘曲位移表达式,导出了曲梁考虑几何非线性情况下的总势能,根据欧拉公式得到了曲梁的稳定平衡方程。推导中采用横截面线性和非线性总应变为零的假定,从而无需考虑横向应力的影响,对应变高阶项采用合理的简化处理,使理论推导过程简单明了。在理论推导的基础上分析了简支拱在均布径向荷载和两端等弯矩荷载作用下的平面内和平面外屈曲问题,并与其他研究者的结果进行了比较,追溯了各理论结果存在差别的根源,论证了本文理论推导过程的合理性。使用通用有限元软件ANSYS进行了模拟,与本文的分析结果一致,证明了所得公式的正确性。通过一些无碍结果的近似使所得公式形式简洁,便于在工程中应用。     

Stability of Laminated Shells Made of Materials with one Plane of Elastic Symmetry

The paper sets forth a technique, based on the Kirchhoff–Love theory of shells, for solving stability problems for thin-walled laminated shells of revolution made of an anisotropic material with one plane of elastic symmetry. The resolving system of differential equations is of the 16th order since the symmetric and asymmetric buckling modes are coupled. The results from a stability analysis of cylindrical shells made of carbon plastics and subjected to compression are analyzed against the angle of the principal directions of elasticity. The influence of boundary conditions is studied. The error due to neglecting the coupling of buckling modes is estimated     

基于升阶谱有限条法的复合材料壁板结构稳定性分析

通过将升阶谱与有限条方法相结合,得到了以多项式级数为形函数的升阶谱有限条方法,并采用该方法对复合材料壁板结构在复杂边界条件下,受轴压、侧压及剪切载荷复合作用下的临界稳定性问题进行分析。数值算例结果表明,该方法综合了升阶谱和有限条的优点,可以快速稳定的精确求解复合材料壁板结构的临界失稳载荷。     

Multigrid Models of Composite Materials of Irregular Structure with a Small Filling Ratio

This paper considers composites consisting of a set of typical composite multigrid finite elements whose structures are regular and different. Mean local errors are proposed for multigrid modeling of composites.     

Dynamic Deformation of a Curved Plate with a Rigid Insert

A general solution is obtained for dynamic bending of ideal rigid-plastic plates with a clamped or simply supported curved contour containing an absolutely rigid insert of an arbitrary shape. The plate is affected by a short-time high-intensity explosive dynamic load uniformly distributed over the surface. It is shown that there are several mechanisms of plate deformation. Equations for dynamic deformation are derived for each mechanism, and conditions of occurrence are analyzed. Examples of numerical solutions are given. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 2, pp. 126–138, March–April, 2006.     

Dispersed Damages in Stability Problems for Doubly Curved Shells of Revolution

An approach is expounded to the study of the bifurcation stability of doubly curved shells of revolution. The microdamage of an isotropic material is considered as empty spherical pores randomly dispersed over the volume, their concentration increasing with load. A damaged inhomogeneous material is modeled by a continuous physically nonlinear medium whose nonlinear deformation depends on how the material fails and the microstrength is distributed. A bifurcation stability problem is formulated based on the concept of continuous loading within the framework of the Kirchhoff–Love hypotheses. As an example, a solution is given to the stability problem on shells of positive Gaussian curvature under external uniform pressure