Local Collocation Method for Prediction of Natural Frequency of Functionally Graded Cylindrical Shells

In this article, the local thin plate spline collocation method and first-order shear deformation shell theory are used to predict the natural frequency of functionally graded cylindrical shells. The local collocation method does not require special treatment for essential boundary condition nor time-consuming integration of weak form. Natural frequency of functionally graded cylindrical shells with clamped and simply supported boundary conditions are solved and compared with available published results to assess the performance of the present method.     

闭口圆柱壳和造粒塔的计算

本文对Flügge圆柱壳精确理论的解作了必要的改进和补充,使Flügge理论便于实用并能解决更多的工程问题。导出圆柱壳塔型结构上端的边界条件。最后将理论成果应用于造粒塔的计算,编制出计算用表。     

汽车覆盖件抗凹性能研究进展

随着汽车轻量化和个性化的发展,汽车车身材料更多的选择铝合金等轻质材料,因此,对于汽车外覆盖件的抗凹性提出了更高和更严苛的要求。主要总结了汽车外覆盖件静态和动态抗凹性能的影响因素,以及在预测分析和评估方面的研究进展,并阐述了为满足实际应用和技术支持的需要,抗凹性测试的设备设计与测试方法的最新进展。     

超音速流动中粘弹性圆柱壳的稳定性

基于薄壳的Karman-Donnell假设、空气动力学中的一阶活塞理论和粘弹性力学中的Boltzmann叠加原理,给出了超音速流动中粘弹性圆柱壳的数学模型。在空域上采用Galerkin方法,并在时域上通过引进新变量,将原来的积分－偏微分系统简化为高维微分系统。利用非线性动力学中的多种方法,考察了自由流动压对粘弹性圆柱壳稳定性的影响。发现气动粘弹性圆柱壳在径向周期激励下具有两种稳定的运动和两种不稳定的运动。     

Transient Dynamic Response of Clamped-Free Hybrid Composite Circular Cylindrical Shells

Dynamic response of multilayer circular cylindrical shells composed of hybrid composite materials subjected to lateral impulse load is studied in this paper. The boundary conditions (B.C.s) are considered to be clamped-free. Both isotropic (metal) and orthotropic (composite) layers are used simultaneously in the hybrid lamination. There is no limitation for fibre orientation. First order shear deformation theory (FSDT) and Love’s first approximation theory are utilized in the shell’s equilibrium equations. Equilibrium equations for free and forced vibration problems of the shell are solved using Galerkin method. Finally, time response of displacement components of Fibre-Metal Laminate (FML) cylindrical shells is derived using mode superposition method. The effect of lay up, material properties, fibre orientation and volume fraction of metal layers on the dynamic response of the shell are investigated. New interesting results are obtained and discussed providing a helpful insight for aircraft structure’s designers.     

Stability and Load-Carrying Capacity of Elastic Reinforced Cylindrical Shells

By using the equilibrium equations in displacements, we develop an analytic method for the evaluation of upper critical loads in elastic cylindrical shells with transverse reinforcement. As a result, we deduce analytic expressions for the evaluation of critical stresses in momentless shells and propose a procedure for the evaluation of the lower limit of the load-carrying capacity of shells based on the application of the method of reduced stiffness. The numerical results are compared with the available theoretical and experimental data. __________ Translated from Problemy Prochnosti, No. 6, pp. 103 – 113, November – December, 2005.     

Stability of Cylindrical Shells with Regard for Dispersed Cracking in the Material

The problems of bifurcation stability of cylindrical shells are stated and solved with regard for the damage to a material in the subcritical stressed state. The appearance of defects in the material is explained by the inhomogeneity of its microstrength. The defects are simulated by a system of plane elliptic and circular cracks statistically uniformly and isotropically distributed over the volume of a shell. The mathematical statement of the problem is performed within the framework of the Kirchhoff–Love hypotheses by using the concept of continued loading. The solution of the problem is constructed for the case of uniform compression of the shell.     

Investigation of the Process of Stability Loss for Smooth Thin-Walled Cylindrical Shells under the Local Action of a Radiation Pulse

It is shown that, under the action of a short-term pulse of external pressure caused by laser radiation, a shell suffers elastic deformation in the course of interaction with the pulse according to the short-wave form on the boundary of the region of loading. When the pulse action is terminated, the shell continues its motion, which is not axially symmetric. As soon as the limiting displacements are attained, the global stability loss is observed. The form of wave formation of the global stability loss in the circumferential direction is determined by the size of the region of loading.     

八宝粥罐装包装凹陷问题调查及分析

目的研究八宝粥产品罐装包装凹陷变形的原因及解决方法。方法首先采用网络问卷的方式对216位消费者进行八宝粥产品包装消费者调查,再通过走访4家大型超市对7种品牌罐装包装八宝粥进行抽样调查,最后选取D牌八宝粥作为调查对象,进行从生产到销售上架的跟踪调查。结果货架上的八宝粥罐装包装凹陷现象较为严重,包装凹陷在一定程度上影响了消费者对八宝粥产品的认知及购买。八宝粥产品罐身凹陷变形出现在生产到销售各个环节,并且随着运输环节的增加,凹陷变形率也增加。结论八宝粥产品罐身凹陷变形主要出现在生产灌装封盖、杀菌冷却环节以及运输装卸环节,其改进可通过对各环节的综合管理得以实现。     

高速旋转圆柱壳的自然频率和临界转速

应用能量法导出对应于任一转速的自然频率和临界转速的计算公式。结果表明每一阶主振动都有正向反向的两种频率。只有在长径比较小条件下才有环向第一阶正向临界转速且数值很大。反向临界转速则在环向第一和第二阶都存在。     

考虑层问作用的冷轧钢卷抗凹性分析

针对冷轧钢卷包装中多层材料的接触变形问题,对钢卷包装系统的抗凹性进行了分析与研究;建立了考虑层间作用的钢卷包装系统的力学模型,计算和分析了钢卷的变形和应力,应用HYPERMESH与ANSYS/LS-DYNA对钢卷抗凹性模型进行了有限元仿真;最后进行了抗凹性模型的冲击试验,验证了有限元仿真计算结果,可为钢卷包装工艺设计提供理论依据。     

复合材料纵横加筋圆柱壳自由振动分析

使用能力法分析了两端简支复合材料纵横加筋圆柱壳的自由振动特性,从Love’s理论出发,分别计算壳体面板和纵横加筋结构的应变能和动能,在计算加筋结构应变能和动能时,将加筋结构的作用影响平均在整个壳体区域。然后代入Lagrange方程得到频率方程。通过比较,计算方法所得到的结果与文献比较吻合。采用平均法计算的结果比采用离散方法计算的结果偏小。还研究了壳体和加筋结构参数的变化对圆柱壳自由振动频率的影响。     

受约束的圆柱壳的振动分析

本文提出的解析法可对具有任意经典边界条件和在两端间具有若干约束的圆柱壳的自振特性进行计算。文中将亮体轴向模态位移用完备正交级数表示,然后将壳体振型函数分解为一个一致收敛级数迭加上另一线性多项式,从而解决了振型级数的收敛性和可微性。这样处理比stokes变换方法更具有一般性,不但可以得到受约束的圆柱壳固有频率的精确值,而且可以求得相应的振型。     

Dynamical Tension of a Hollow Cylindrical Specimen with Circular Crack

We propose a method for determining dynamic stress intensity factors for hollow cylindrical specimens with circular crack of finite length under impact tension. The solution of this problem is reduced to the numerical solution of an eigenvalue problem with the use of experimental loading–time diagrams. Simple formulas are obtained for determining dynamic stress intensity factors, depending on the history of loading of a specimen. The comparison of the values of dynamic stress intensity factors calculated by the formulas indicated and by the finite-element method testifies to the reliability of the results obtained.     

A Refined Asymptotic Theory for the Nonlinear Analysis of Laminated Cylindrical Shells

Within the framework of the three-dimensional (3D) nonlinear elasticity, a refined asymptotic theory is developed for the nonlinear analysis of laminated circular cylindrical shells. In the present formulation, the basic equations including the nonlinear relations between the finite strains (Green strains) and displacements, the nonlinear equilibrium equations in terms of the Kirchhoff stress components and the generalized Hooke's law for a monoclinic elastic material are considered. After using proper nondimensionalization, asymptotic expansion, successive integration and then bringing the effects of transverse shear deformation into the leading-order level, we obtain recursive sets of the governing equations for various orders. It is shown that the von Karman-type first-order shear deformation theory (FSDT) is derived as a first-order approximation to the 3D nonlinear theory. The differential operators in the linear terms of governing equations for the leading order problem remain identical to those for the higher-order problems. The nonlinear terms related to the unknowns of the current order appear in a regular pattern and the other nonhomogeneous terms can be calculated by the lower-order solutions. It is also illustrated that the nonlinear analysis of laminated circular cylindrical shells can be made in a hierarchic and consistent way.     

Effect of the Stress State on the Critical Load and Load-Carrying Capacity of Shells with Axisymmetrical Dents

A method of approximate determination of critical stresses in elastic near-cylindrical shells with the use of equations in terms of displacements is proposed. Analytical expressions to estimate critical stresses in membrane unstiffened shells were obtained. Two distributions of internal forces, namely, the forces constant and variable in magnitude, were analyzed.     

Generalization of the Classical Formula of Stability of Cylindrical Shells to the Case of Spiral Stiffeners

The stability of a cylindrical shell with eccentric spiral stiffeners in the case of axial compression is considered. A simple computational formula for determination of the critical stress has been obtained. The formula contains all the necessary mechanical and geometric characteristics of the shell and the stiffeners and is, in essence, a generalization of the well-known and widely used classical formula for isotropic smooth shells. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 4, pp. 197–200, July–August, 2005.