Vibration of cylindrical shells with ring support

In this paper, a study on the vibration of thin cylindrical shells with ring supports is presented. The cylindrical shells have ring supports which are arbitrarily placed along the shell and which imposed a zero lateral deflection. The study is carried out using Sanders' shell theory. The governing equations are obtained using an energy functional with the Ritz method. Results are presented on the frequency characteristics, influence of ring support position and the influence of boundary conditions. The present analysis is validated by comparing results with those available in the literature.     

Exact solutions for vibration of cylindrical shells with intermediate ring supports

This paper presents new exact solutions for vibration of thin circular cylindrical shells with intermediate ring supports, based on the Goldenveizer–Novozhilov shell theory (Theory of thin shells; The theory of thin elastic shells). An analytical method is proposed to study the vibration behaviour of the ring supported cylindrical shells. In the proposed method, the state-space technique is employed to derive the homogenous differential equation system for a shell segment and a domain decomposition approach is developed to cater for the continuity requirements between shell segments. Exact frequency parameters are presented in tables and design charts for circular cylindrical shells having multiple intermediate ring supports and various combinations of end support conditions. These exact vibration frequencies may serve as important benchmark values for researchers to validate their numerical methods for such circular cylindrical shell problems.     

Vibration of functionally graded cylindrical shells based on different shear deformation shell theories with ring support under various boundary conditions

In the present work, study of the vibration of thin cylindrical shells with ring supports made of a functionally gradient material (FGM) composed of stainless steel and nickel is presented. Material properties are graded in the thickness direction of the shell according to volume fraction power law distribution. Effects of boundary conditions and ring support on the natural frequencies of the FGM cylindrical shell are studied. The cylindrical shells have ring supports which are arbitrarily placed along the shell and which imposed a zero lateral deflection. The study is carried out using different shear deformation shell theories. The analysis is carried out using Hamilton’s principle. The governing equations of motion of a FGM cylindrical shells are derived based on various shear deformation theories. Results are presented on the frequency characteristics, influence of ring support position and the influence of boundary conditions. The present analysis is validated by comparing results with those available in the literature. This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin M. M. Najafizadeh received his BS degree in 1995 from Azad University (Arak) and the Ms Degree in 1997 from Azad University (Arak), and his Ph.D. degree in 2003 from Science and Research Branch Islamic Azad University (Tehran, Iran), all in mechanical Engineering. He is member of faculty in Islamic Azad University (Arak) since 1998. He teaches courses in the areas of dynamics, theory of plates and shells and finite element method. He has published more than 20 articles in journals and conference proceeding. Mohammad Reza Isvandzibaei received his Ms Degree from Azad University (Arak), and now he is the student of Ph.D. in university of Pune, (India) all in mechanical Engineering. He is member of faculty in Islamic Azad University (Andimeshk).     

弹性圆柱壳的稳定性优化设计

研究任意轴对称边界条件下和受均布法向载荷作用圆柱壳的稳定性优化设计问题，即极大化屈曲临界载荷。利用能量原理分析轴对称变厚度圆柱壳的分支点屈曲，将求解屈曲临界载荷变成求解广义特征值方程，使圆柱壳稳定性优化设计成为极大化最小特征值问题。实际算例验证了本方法的有效性。研究结果可用于圆柱壳的加肋优化设计。     

三塔悬索桥地震响应控制

以三塔悬索桥型的泰州大桥为工程背景,研究了3种不同桥梁减震措施的减震效果:弹性拉索、粘滞阻尼器、弹性拉索与粘滞阻尼器.弹性连接和粘滞阻尼器提高结构刚度与阻尼以减小结构地震响应.研究结果表明,塔梁间弹性拉索和粘滞阻尼器均可有效减小梁端纵向位移峰值,并使其振动快速衰减,其中以同时设置弹性拉索与粘滞阻尼器的减震效果为最佳.与...     

潜水深度对结构自振特性影响的数值分析

水下结构的自振特性不仅受流体动压力的影响，还受不同水深一的静水压力的影响，本文假设水为无粘、不可压、无旋流体，通过附连水质量解耦，用考虑初应力刚度的有限元方法计算了圆柱壳在不同水深下的自振特性，初步揭示了这种影响，所得结果和方法可供流固耦合方面的研究参考。     

Frequency analysis of multiple layered cylindrical shells under lateral pressure with asymmetric boundary conditions

Natural frequency characteristics of a thin-walled multiple layered cylindrical shell under lateral pressure are studied. The multiple layered cylindrical shell configuration is formed by three layers of isotropic material where the inner and outer layers are stainless steel and the middle layer is aluminum. The multiple layered shell equations with lateral pressure are established based on Love＇s shell theory. The governing equations of motion with lateral pressure are employed by using energy functional and applying the Ritz method. The boundary conditions represented by end conditions of the multiple layered cylindrical shell are simply supported-clamped（SS-C）, free-clamped（F-C） and simply supported-free（SS-F）. The influence of different lateral pressures, different thickness to radius ratios, different length to radius ratios and effect of the asymmetric boundary conditions on natural frequency characteristics are studied. It is shown that the lateral pressure has effect on the natural frequency of multiple layered cylindrical shell and causes the natural frequency to increase. The natural frequency of the developed multilayered cylindrical shell is validated by comparing with those in the literature. The proposed research provides an effective approach for vibration analysis shell structures subjected to lateral pressure with an energy method.     

Investigating elastic stability of cylindrical shell with an elastic core under axial compression by energy method

In this paper, the elastic axisymmetric buckling of a thin, isotropic and simply supported cylindrical shell with an elastic core under axial compression has been analyzed using energy method. The nonlinear strain-displacement relations in general cylindrical coordinates are simplified using Sanders kinematic relations (Sanders, 1963) for axial compression. Equilibrium equations are obtained by using minimum potential energy together with Euler equations applied for potential energy function in cylindrical shell. To acquire stability equation of cylindrical shell with an elastic core, minimum potential energy theory and Trefftz criteria are implemented. Stability and compatibility equations for an imperfect cylindrical shell with an elastic core are also obtained by the energy method, and the buckling analysis of shell is carried out using Galerkin method. Critical load curves versus the aspect ratio are obtained and analyzed for a cylindrical shell with an elastic core. It is concluded that the application of an elastic core increases elastic stability and significantly reduces the weight of cylindrical shells.     

A study on stress analysis of orthotropic composite cylindrical shells with a circular or an elliptical cutout

The stress analysis on orthotropic composite cylindrical shells with one circular or one elliptical cutout subjected to an axial force is carried out by using an analytical and experimental method. The composite cylindrical shell governing equation of the Donnell's type is applied to this study and all results are presented by the stress concentration factor. The stress concentra-tion factor is defined as the ratio of the stress on the region around a cutout to the nominal stress of the shell. The stress concentration factor is classified into the circumferential stress concen-tration factors and the radial stress concentration factors due to the cylindrical coordinate of which the origin is the center of a cutout. The considered loading condition is only axial tension loading condition. In this study, thus, the maximum stress is induced on perpendicular region against axial direction, on the coordinate. Various cutout sizes are expressed using the radius ratio,, which is the radius of a cutout over one of the cylindrical shell. Experimental results are obtained using strain gages, which are attached around a cutout of the cylindrical shell. As the result from this study, the stress concentration around a cutout can be predicted by using the analytical method for an orthotropic composite cylindrical shell having a circular or an elliptical cutout.     

Analysis of the vibration behavior of FGM cylindrical shells including internal pressure and ring support effects based on Love-Kirchhoff theory with various boundary conditions

This paper presents the study on vibration behavior of functionally graded material (FGM) cylindrical shell with the effects of internal pressure and ring support. The FGM properties are graded along the thickness direction of the shell. The FGM shell equations with internal pressure and ring support are established based on strain-displacement relationship using Love-Kirchhoff shell theory. The governing equations of motion were solved by using energy functional and by applying Ritz method. The boundary conditions represented by end conditions of the FGM cylindrical shell are simply supported-simply supported (SS-SS), clamped-clamped (C-C), free-free (F-F), clamped-free (C-F), clamped-simply supported (C-SS), free-simply supported (F-SS), free-sliding (F-SL) and clamped-sliding (C-SL). To check the validity and accuracy of the present method, the results obtained are compared with those available in the literature. The influence of internal pressure, ring support position and the effect of the different boundary conditions on natural frequencies characteristics are studied. These results presented can be used as important benchmark for researchers to validate their numerical methods when studying natural frequencies of shells with internal pressure and ring support.     

圆柱形壳体最小质量可靠性优化设计

给出了圆柱形壳体的主要失效模式判据和失效应力的计算方法，然后按照壳体的设计要求和工作条件，建立了可靠性优化设计的目标函数（壳体质量最小）和约束条件的数学模型，最后给出了分别加Ｔ形、Ｉ型和Ｚ型肋壳体的可靠性优化设计实例。结果表明：在满足可靠性要求条件下，本文方法具有使圆柱形壳体的质量减小、尺寸合理和性能提高的优点，是一种有效的工程设计方法．     

Heat state of pendulum sliding bearings under seismic effects

Issues in the choice of self-lubricating antifrictional materials for pendulum sliding bearings used as seismic dampers are discussed. Such bearings are used in supports of essential constructions (including offshore drilling platforms) and other objects located in seismically dangerous regions to protect buildings from loads caused by earthquakes and other power effects. The heat state of seismic dampers is studied using various computer programs. The computation method suggested allows the selection of antifrictional materials for sliding bearings with account for their temperature resistance.     

Strip Layer Method for Analysis of the Three-Dimensional Stresses and Spread of Large Cylindrical Shell Rolling

As the traditional forging process has many problems such as low efficiency, high consumption of material and energy, large cylindrical shell rolling is introduced. Large cylindrical shell rolling is a...     

带齿薄壁短圆筒振动试验模型的相似设计方法

针对带齿薄壁短圆筒振动分析的试验模型简化问题,基于相似理论提出一种动力学相似模型的设计方法。以带3个锥形齿的薄壁短圆筒为典型研究对象,应用Donnell非线性应变-位移理论建立数学模型,得到带锥形齿薄壁短圆筒的频率方程,并使用量纲分析法建立带锥形齿薄壁短圆筒原型与完全几何相似模型的动力学相似关系,在此基础上,重点研究简化为不完全几何相似的相似模型设计方法,并推导了理论计算公式。为简化说明,以将薄壁短圆筒上3个锥形齿简化为T形齿为例,分别给出将其中1个锥形齿简化为T形齿、2个相邻较近的锥形齿简化为1个T形齿和3个锥形齿简化为2个T形齿等三种不同情况的设计方法,并采用有限元法对简化前后的原型和模型的固有特性进行对比,验证了所提出相似设计方法的有效性和正确性。     

Vibration analysis of submerged thin FGM cylindrical shells

This study gives a brief work on vibration characteristics of cylindrical shells submerged in an incompressible fluid. The shell is presumed to be structured from functionally graded material. The effect of the fluid is introduced by using the acoustic wave equation. Love’s first order thin shell theory is utilized in the shell dynamical equations. The problem is framed by combining shell dynamical equations with the acoustic wave equation. Fluid-loaded terms are associated with Hankel function of second kind. Wave propagation approach is employed to solve the shell problem. Some comparisons of numerical results are performed for the natural frequencies of simply supported-simply supported, clamped-clamped and clamped-simply supported boundary conditions of isotropic as well as functionally graded cylindrical shells to check the validity of the present approach. The influence of fluid on the submerged functionally graded cylindrical shells is noticed to be very pronounced.     

Vibrations of cantilevered circular cylindrical shells: Shallow versus deep shell theory

Free vibrations of cantilevered circular cylindrical shells having rectangular plan-forms are studied in this paper by means of the Ritz method. The deep shell theory of Novozhilov and Goldenveizer is used and compared with the usual shallow shell theory for a wide range of shell parameters. A thorough convergence study is presented along with comparisons to previously published finite element solutions and experimental results. Accurately computed frequency parameters and mode shapes for various shell configurations are presented. The present paper appears to be the first comprehensive study presenting rigorous comparisons between the two shell theories in dealing with free vibrations of cantilevered cylindrical shells.     

Frequency response analysis of cylindrical shells conveying fluid using finite element method

A finite element vibration analysis of thin-watled cylindrical shells conveying fluid with uniform velocity is presented The dynamic behavior of thin-walled shell is based on the Sanders’ theory and the fluid in cyhndrical shell is considered as inviscid and incompressible so that it satisfies the Laplace’s equation A beam-like shell element is used to reduce the number of degrees-of-freedom by restricting to the circumferential modes of cylindrical shell An estimation of frequency response function of the pipe considering of the coupled effects of the internal fluid is presented A dynamic coupling condition of the interface between the fluid and the structure is used The effective thickness of fluid according to circumferential modes is also discussed The influence of fluid velocity on the frequency response function is illustrated and discussed The results by this method are compared with published lesults and those by commercial tools     

THEORETICAL PREDICTION OF SOUND RADIATION FROM A HEAVY FLUID-LOADED CYLINDRICAL COATED SHELL

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薄壁柱壳零件的加工稳定性分析

根据薄壁柱壳在切削加工中的力学特点,应用有限元软件ANSYS建立了一类悬臂柱壳结构的有限元模型。对不同几何参数、切削力作用点和切削分力时柱壳的稳定性进行了分析。结果表明在切削力一定的情况下,较小曲率半径、弦长和壁厚的柱壳结构易发生屈曲变形;同时当几何参数不变时,合理设计各分力比例和装夹方式能够有效避免失稳。     

开孔圆柱壳模拟疲劳试验模型及加载条件的研究

研究受内压开孔圆柱壳与其受拉伸开孔平板模型在结构和受载条件上的相似性，有限元分析表明，开孔圆柱壳与其相应的平板模型在开孔附近的等效应力分布非常相似，分析和试验结果表明，开孔圆柱壳模拟疲劳试验载荷应由控制疲劳寿命的关键部位（即危险点）的等效应力来确定，当开孔圆柱壳与其平板模型在危害点的等效应力水平和分布相同时，可认为二者的疲劳寿命也相同，在正确的加载条件下，开孔平板模型可用于开孔圆柱壳的模拟疲劳试验，并较精确地预测开孔圆柱壳的疲劳寿命。