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1.
变厚度圆柱壳的强度优化设计 总被引:5,自引:0,他引:5
对在任意轴对称分布荷载作用下体积保持常数的变厚度圆柱壳的强度优化设计问题进行了研究。当中面形状固定时 ,采用阶梯折算法 ,用传递矩阵导出了变厚度圆柱壳的初参数解的显式表达式。根据Huber-Mises-Hencky强度准则 ,将变厚度圆柱壳的强度优化转化为极小化当量应力的非线性规划问题 ,并采用投影梯度法建立了问题的优化方法。文中对几个典型问题进行了计算。与等厚度圆柱壳相比较 ,优化圆柱壳的最大当量应力得到了显著降低。本文的研究方法和结果可以用于指导大型圆柱壳体的加肋设计 相似文献
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G. V. Filatov 《International Applied Mechanics》2005,41(8):917-923
The paper is concerned with the mass optimization of a smooth cylindrical shell subjected to short-term aperiodic loads in
the form of axial compression pulses. The optimization method chosen is random search with controlled limits of optimized
parameters. The effect of the pulse duration and the load level on the optimal design is analyzed. The results obtained by
two methods are compared
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Translated from Prikladnaya Mekhanika, Vol. 41, No. 8, pp. 97–104, August 2005. 相似文献
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本文从偏心圆柱壳截面的几何特性出发,将偏心圆柱壳问题转化为一个周向变厚度圆柱壳问题,随后利用其状态向量之间的传递矩阵将壳体的振动控制方程转化为矩阵微分方程形式,通过Magnus级数法求解传递矩阵得到频率方程。采用Lagrange插值法得到偏心圆柱壳体自由振动状态下的固有频率,并且与圆柱壳的固有频率进行了比较。对影响结构固有频率的主要参数进行了分析,得到了这些参数和固有频率之间的关系。本文不仅提出了一种有效求解偏心圆柱壳固有频率的新方法,同时亦可为检测偏心圆柱壳的偏心距提供一种新的思路和方法。 相似文献
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The questions investigated in this paper are related to an important class of problems of optimal design of structures against brittle fracture. The primary problem of axisymmetric shell optimization under fracture mechanics constraint is formulated as the weight (volume of the shell material) minimization under stress intensity constraints. Considered problems are characterized by incomplete information concerning crack size, crack location and its orientation. Taking into account the factor of incomplete information the paper presents the formulation of optimal shell design problem based on minimax (guaranteed) approach and provides some results of analytical investigation for thin-walled shells with through cracks. 相似文献
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The paper analyzes the nonlinear deformation of a current-carrying thin shell in coupled electromagnetic and mechanical fields.
The nonlinear magnetoelastic kinetic equations, physical equations, geometric equations, electrodynamic equations, expressions
for the Lorentz force of a current-carrying thin shell in a coupled field are given. The normal Cauchy form nonlinear differential
equations that include ten basic unknown functions are obtained by the variable replacement method. The difference and quasi-linearization
methods are used to reduce the nonlinear magnetoelastic equations to a sequence of quasilinear differential equations that
can be solved by discrete orthogonalization. Numerical solutions for the stresses and strains in a current-carrying thin strip
shell with two edges simply supported are obtained as an example. The dependence of the stresses and strains in the current-carrying
thin strip shell on the electromagnetic parameters is discussed. In a special case, it is shown that the deformation of the
shell can be controlled by changing the electromagnetic parameters 相似文献
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《International Journal of Solids and Structures》2007,44(3-4):1145-1160
Thin-walled, cylindrical structures are found extensively in both engineering components and in nature. The weight to load bearing ratio is a critical element of design of such structures in a variety of engineering applications, including space shuttle fuel tanks, aircraft fuselages, and offshore oil platforms. In nature, thin-walled cylindrical structures are often supported by a honeycomb- or foam-like cellular core, as for example, in plant stems, porcupine quills, or hedgehog spines. Previous studies have suggested that a compliant core increases the buckling resistance of a cylindrical shell over that of a hollow cylinder of the same weight. In this paper, we extend the linear-elastic buckling theory by coupling it with basic plasticity theory to provide a more comprehensive analysis of isotropic, cylindrical shells with compliant cores. We examine the optimal design of a thin-walled cylinder with a compliant core, of given radius and specified materials, for a prescribed load bearing capacity in axial compression. The analysis gives the values of the shell thickness, the core thickness, and the core density that maximize the load bearing capacity of the shell with a compliant core over an equivalent weight hollow shell. The analysis also identifies the optimum ratio of the core modulus to the shell modulus and is supported by a Lagrangian optimization technique. The analysis further discusses the selection of materials in the design of a cylinder with a compliant core, identifying the most suitable material combinations. The performance of a cylinder with a compliant core is compared with competing designs (optimized hat-stiffened shell and optimized sandwich-wall shell). Finally, the challenges associated with achieving the optimal design in practice are discussed, and the potential for practical implementation is explored. 相似文献
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A theoretical investigation is undertaken into the dynamic instability of complete spherical shells which are loaded impulsively and made from either linear elastic or elastic-plastic materials. It is shown that certain harmonics grow quickly and cause a shell to exhibit a wrinkled shape which is characterized by a critical mode number. The critical mode numbers are similar for spherical and cylindrical elastic shells having the same R/h ratios and material parameters, but may be larger or smaller in an elastic-plastic spherical shell depending on the values of the various parameters. Threshold velocities are also determined in order to obtain the smallest velocity that a shell can tolerate without excessive deformation. The threshold velocities for the elastic and elastic-plastic spherical shells are larger than those which have been published previously for cylindrical shells having the same R/h ratios and material parameters. 相似文献
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成祥生 《应用数学和力学(英文版)》1986,7(3):279-284
The present paper discusses a method of optimal design of the shallow shell with double curvature on the elastic foundation Substantially we take the initial flexural function as the control function or design variable which will be found and the potential energy of the external loads as the criterion of quality of the optimal design of the shallow shell with double curvature, therefore the functional of the potential energy will be aim function. The optimal conditions and the isoperimetric conditions belong to the constrained conditions. thus we obtain the necessary conditions of the optimal design for the given problems, at the same time the conjugate function is introduced, then the problems are reduced to the solutions of two boundary value problems for the differential equation of conjugate function and the initial flexual function. 相似文献
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波纹壳是传感器弹性元件的一类重要形式,也是精密仪器仪表弹性元件中的一类重要形式。由于波纹壳形状复杂、参数众多、厚度薄,对其进行非线性分析非常重要同时也是十分困难的。本文考虑一种在传感器弹性元件中有重要应用价值的正弦波纹浅球壳体,将这种壳体视为结构上的圆柱正交异性扁球壳,根据Andryewa的思想,分别得到了正弦波纹壳径向、环向在拉伸、弯曲下的等价的四个各向异性参数;建立了正弦波纹扁球壳的非线性强迫振动微分方程;得到了正弦波纹扁球壳非线性强迫振动的共振周期解及幅频特性曲线。 相似文献
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Yu. V. Nemirovskii A. P. Yankovskii 《Journal of Applied Mechanics and Technical Physics》2000,41(4):725-733
The initial boundary-value heat-conduction problem for shells reinforced by tubes filled with a flowing liquid heat-transfer
agent is considered. The dependence of the coefficients in the heat-conduction equations on the thermophysical characteristics
of the composition phases, reinforcement parameters, and shell geometry is studied. A comparative analysis of the stationary
temperature fields in thin shells of revolution of different Gaussian curvature is performed for various reinforcement structures
and heat-exchange regimes. It is shown that the temperature distribution in the shells depends strongly on the reinforcement
structure and the shell geometry, which opens up new possibilities of designing optimal structures.
Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated
from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 4, pp. 168–177, July–August, 2000. 相似文献
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Partial separation of variables and reexpansion of cylindrical and plane waves are used to find the solution describing the
uniform motion of a load along a thin circular cylindrical shell in an elastic half-space with the free surface parallel to
the axis of the shell. This is a model problem for studying the dynamics of tunnels and shallow-buried pipelines under transport
loads. Dispersion curves for the cases of sliding and tight contact between the shell and the half-space are plotted and analyzed.
The effect of the shell parameters on the stress–strain state of the half-space is examined 相似文献
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A. Ghanei E. Assareh M. Biglari A. Ghanbarzadeh A. R. Noghrehabadi 《Heat and Mass Transfer》2014,50(10):1375-1384
Many studies are performed by researchers about shell and tube heat exchanger (STHE) but the multi-objective particle swarm optimization (PSO) technique has never been used in such studies. This paper presents application of thermal-economic multi-objective optimization of STHE using PSO. For optimal design of a STHE, it was first thermally modeled using e-number of transfer units method while Bell–Delaware procedure was applied to estimate its shell side heat transfer coefficient and pressure drop. Multi objective PSO (MOPSO) method was applied to obtain the maximum effectiveness (heat recovery) and the minimum total cost as two objective functions. The results of optimal designs were a set of multiple optimum solutions, called ‘Pareto optimal solutions’. In order to show the accuracy of the algorithm, a comparison is made with the non-dominated sorting genetic algorithm (NSGA-II) and MOPSO which are developed for the same problem. 相似文献
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Shahid Hussain Arshad Muhammad Nawaz Naeem Nazra Sultana Abdul Ghafar Shah Zafar Iqbal 《Archive of Applied Mechanics (Ingenieur Archiv)》2011,81(3):319-343
In the present study, a vibration frequency analysis of a bi-layered cylindrical shell composed of two independent functionally
graded layers is presented. The thickness of the shell layers is assumed to be equal and constant. Material properties of
the constituents of bi-layered functionally graded cylindrical shell are assumed to vary smoothly and continuously through
the thickness of the layers of the shell and are controlled by volume fraction power law distribution. The expressions for
strain–displacement and curvature–displacement relationships are utilized from Love’s first approximation linear thin shell
theory. The versatile Rayleigh–Ritz approach is employed to formulate the frequency equations in the form of eigenvalue problem.
Influence of material distribution in the two functionally graded layers of the cylindrical shells is investigated on shell
natural frequencies for various shell parameters with simply supported end conditions. To check the validity, accuracy and
efficiency of the present methodology, results obtained are compared with those available in the literature. 相似文献
19.
G. S. Leizerovich S. V. Seregin 《Journal of Applied Mechanics and Technical Physics》2016,57(5):841-846
The effect of a small added mass on the frequency and shape of free vibrations of a thin shell is studied using shallow shell theory. The proposed mathematical model assumes that mass asymmetry even in a linear formulation leads to coupled radial flexural vibrations. The interaction of shape-generating waves is studied using modal equations obtained by the Bubnov–Galerkin method. Splitting of the flexural frequency spectrum is found, which is caused not only by the added mass but also by the wave-formation parameters of the shell. The ranges of the relative lengths and shell thicknesses are determined in which the interaction of flexural and radial vibrations can be neglected. 相似文献
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The nonlinear analysis with an analytical approach on dynamic torsional buckling of stiffened functionally graded thin toroidal shell segments is investigated. The shell is reinforced by inside stiffeners and surrounded by elastic foundations in a thermal environment and under a time-dependent torsional load. The governing equations are derived based on the Donnell shell theory with the von K′arm′an geometrical nonlinearity,the Stein and McE lman assumption, the smeared stiffeners technique, and the Galerkin method. A deflection function with three terms is chosen. The thermal parameters of the uniform temperature rise and nonlinear temperature conduction law are found in an explicit form. A closed-form expression for determining the static critical torsional load is obtained. A critical dynamic torsional load is found by the fourth-order Runge-Kutta method and the Budiansky-Roth criterion. The effects of stiffeners, foundations, material,and dimensional parameters on dynamic responses of shells are considered. 相似文献