STRESS CONCENTRATIONS IN CYLINDRICAL SHELLS WITH LARGE OPENINGS

Based on Donnell's shallow shell equation, a new method is given in this paper to ana-lyze theoretical solutions of stress concentrations about cylindrical shells with large openings. With themethod of complex variable function, a series of conformal mapping functions are obtained from dif-ferent cutouts' boundary curves in the developed plane of a cylindrical shell to the unit circle. And,the general expressions for the equations of a cylindrical shell, including the solutions of stress concen-trations meeting the boundary conditions of the large openings' edges, are given in the mapping plane.Furthermore, by applying the orthogonal function expansion technique, the problem can be summa-rized into the solution of infinite algebraic equation series. Finally, numerical results are obtained forstress concentration factors at the cutout's edge with various opening's ratios and different loadingconditions. This new method, at the same time, gives a possibility to the research of cylindrical shellswith large non-circular openings or with nozzles.     

圆柱壳稳定性问题的研究进展

圆柱壳是工程实际中广泛应用的结构,其主要破坏形式是屈曲失稳．作为力学领域的经典问题,圆柱壳稳定性问题的研究非常之多．其中,受均匀轴向压力的圆柱壳由于临界屈曲载荷的理论预测值与早期试验结果之间的巨大差异,更是推动了壳体稳定性理论的不断发展．本文简要回顾了壳体稳定性理论的发展和分类,并对轴压圆柱壳体试验结果分散且远低于理论预测值的原因及含缺陷圆柱壳体的稳定性研究方法进行了总结,然后综述了地下空间顶管、储油罐、加筋圆柱壳及脱层圆柱壳等实际工程中广泛应用的圆柱壳结构稳定性研究的现状和趋势,最后展望了将来对工程应用中圆柱壳结构的稳定性研究的难点和方向．     

可渗透圆柱壳流固耦合问题的流场与内力分析

在弹性薄壳的非线性理论和流体力学基本方程的基础上,研究了可渗透圆柱壳的流固耦合问题.假定壳体具有均布孔隙且孔的面积很小,不考虑其阻力,忽略对弯曲刚度和壳体腔内流体微小运动影响,应用相容欧拉--拉格朗日法建立了带孔的圆柱壳在流体中相互作用的基本方程.通过具体算例求解,给出了流场速度与压力的变化、圆柱壳的变形及内力分布,并对相关参数进行了讨论.     

Buckling and postbuckling of stiffened cylindrical shells under axial compression

Buckling and postbuckling behaviors of perfect and imperfect,stringer andorthotropically stiffened cylindrical shells have been studied under axial compression.Based on the boundary layer theory for the buckling of thin elastic shells suggested in ref.[1],a theoretical analysis is presented.The effects of material properties of stiffeners andskin,which are made of different materials,on the buckling load and postbuckling behaviorof stiffened cylindrical shells have also been discussed.     

轴向冲击下圆柱壳非轴对称屈曲耗散能分析

主要研究受轴向冲击圆柱壳非对称屈曲耗能,从轴向屈曲变形、环向屈曲变形和轴向压 缩变形3个角度进行理论推导. 结果表明: 环向屈曲变形能随屈曲折叠边数增加有减小 趋势, 且占总耗能比例很小,可知圆柱壳受轴向冲击屈曲过程中外力做功主要转变为轴向变形 能,环向屈曲变形消耗外力功很少.     

Analysis of shells reinforced by massive stiffening ribs

The paper presents results of applying a heterogeneous mathematical model “elastic body–Timoshenko shell” to design shells with massive ribs. Numerical results are obtained for a cylindrical shell with ribs. They are compared with results obtained using the theory of elasticity and the theory of Timoshenko shells with piecewise-constant thickness Published in Prikladnaya Mekhanika, Vol. 44, No. 11, pp. 132–142, November 2008.     

Free vibration of layered cylindrical shells filled with fluid

The vibration of the layered cylindrical shells filled with a quiescent, incompressible, and inviscid fluid is analyzed. The governing equations of the cylindrical shells are derived by Love’s approximation. The solutions of the displacement functions are assumed in a separable form to obtain a system of coupled differential equations in terms of the displacement functions. The displacement functions are approximated by Bickley-type splines. A generalized eigenvalue problem is obtained and solved numerically for the frequency parameter and an associated eigenvector of the spline coefficients. Two layered shells with three different types of materials under clamped-clamped (C-C) and simply supported (S-S) boundary conditions are considered. The variations of the frequency parameter with respect to the relative layer thickness, the length-to-radius ratio, the length-to-thickness ratio, and the circumferential node number are analyzed.     

圆柱薄壳稳定性的一个修正理论

著名的唐乃尔(Donnell)——穆什塔利的简化壳体理论只能较精确地适用于较短圆柱壳稳定性计算.其近似性误差随长度与半径之比的增加而增大.本文考虑了横向切力的影响,对非完善型圆柱壳体推导了几何非线性理论的基本方程,建立了对各种长度半径比的圆柱壳体稳定性均适用的修正理论.     

自由圆柱壳体在侧向非对称脉冲载荷下的塑性破坏

将壳体作为理想刚塑性材料，给出了两端自由金属圆柱薄壳体承受侧向非对称脉冲载荷下的变形和运动方程。针对矩形脉冲载荷，给出能量损耗分析。极高载情况下，２／３的外部输入能量转化为塑性功，其余的用于壳体的刚体运动。针对复杂结构的自由圆柱壳，能量法用于分析其破坏。理论预测与实验结果吻合较好。     

层合圆柱壳的振动与横向应力

应用分层壳理论并在壳厚方向彩二次插值函数推导出正交层合圆醉壳的动力学方程,并得出了简支层合圆柱壳自由振动方程的解,所给出的振动频率与三维分析的结果吻合良好,计算了前四阶模态对应的壳中应力,与第三、四阶模态对应的横向正应力与面内应力的比值远高于第一、二阶模态的应力比,计算结果说明,很高的横向正应力是高频动力响应中导致分层壳脱层破坏的一个主要因素。     

Studies on the torsional buckling of elastic cylindrical shells

The experimental phenomenon and theoretical analysis are given for the torsional buckling of elastic cylindrical shells. From the experiment, it is found that the postbuckling deformation doesn't occupy the whole length when the shell is longer. In the theoretical calculation, only the normal displacement boundary condition is taken into account. By comparing the present calculation results with the accurate result of Yamakis theory and the results of the present experiment, it is shown that the influence of the axial and circumference boundary condition is less important.     

薄壁柱壳在内部爆炸载荷下膨胀断裂的研究

以柱形爆炸装置为研究对象 ,讨论了其薄壁壳体在爆炸载荷下的动态断裂准则。给出了典型的FAE模型及在数值计算时必要的简化条件。对回收的壳壁破片进行了SEM扫描电镜观测 ,分析了金属材料在高应变率下膨胀断裂的微观机制。采用解耦的、考虑应变强化的粘塑性本构方程 ,根据损伤破坏理论推导出以临界应变为依据的改进断裂准则 ,计算表明断裂参数理论解与数值模拟结果一致 ,并得到了实验方面的例证。     

拉载下周向壁穿裂纹圆柱壳的弹塑性解析解

基于薄壳理论及Ｄｕｇｄａｌｅ模型,建立了一套相当完整的拉载下周向壁穿裂纹圆柱壳的弹塑性解析解．该解包括裂纹扩展并可应用至裂纹断面完全塑性     

On the stress concentration in thick cylindrical shells with an arbitrary cutout

1.IntroductionThefocusofmuch'researcllforalongtimehasbeenontheinvestigationofstressconcentrationsofthincylindricalshellsll--41.Thestressproblemisdiscussedinreferences[5,6].Whentheratioofthicknesshofshellstothecutoutsizeroisnotrathersmall,thegoverningequationofReissuer'sshallowshellincludingtheeffectoftransversesheardeformationsmustbeusedl7-sl.Thethickshelltheorymakesupweaknessesoftheclassicaltheoryofthinshells.Thetheoryofthickshellscanbeusedforanalyzingstressconcentrationsofcircularcylindrica…     

轴向应力波作用下圆柱壳塑性轴对称动力屈曲

运用有限元特征值分析方法对应力波作用下圆柱壳塑性轴对称动力失稳问题进行了研究。基于应力波理论和相邻平衡准则导出了圆柱壳轴对称动力失稳时的特征方程,在分析中同时考虑了应力波效应及横向惯性效应,把圆柱壳塑性动力失稳问题归结为特征值问题。通过引入圆柱壳动力失稳时的波前约束条件实现了此类问题的有限元特征值解法。计算结果揭示了圆柱壳塑性轴对称动力屈曲变形发展的机理,以及轴向应力波和屈曲变形的相互作用规律。     

含裂纹圆柱薄壳的动态特性试验研究

 利用时间平均法分别拍摄了含轴向和环向裂纹圆柱薄壳的激光 全息振型图，讨论了裂纹对圆柱薄壳振型及固有频率的影响，把含裂 纹壳体的振型分为三个区，即：裂纹周围的局部振动区，壳体原振动 区和过渡区. 并着重分析了局部振动的特征，得出了局部振动有着自 己的独有振形和固有频率的结论，从而很好解释了含裂纹圆柱薄壳的 复杂振型图及固有频率的反常变化.     

Analysis of energy release rate for composite delaminated cylindrical shells subjected to axial compression

In this paper, the postbuckling governing equations and the analytical expression of the energy release rates associated with delamination growth in a compression-loaded cylindrical shell are derived by using the variational principle of moving boundary and the Griffith fracture criterion. The finite difference method is used to generate the postbuckling solutions of the delaminated cylindrical shells, and with these solutions, the values of the energy release rates are determined. In simulational examples, the effects of a wide range of parameters, such as delamination sizes and depths, boundary conditions, geometrical parameters, material properties and laminate stacking sequences on the energy release rates of axisymmetrical laminated cylindrical shells are intensively discussed.The English text was polished by Yunming Chen.     

轴向冲击圆柱壳非弹性响应

简要论述承受轴向冲击载荷圆柱壳非弹性动屈曲响应的研究进展。采用Ｋａｒｍａｎ－Ｄｏｎｎｅｌｌ运动方程研究轴向流固冲击载荷作用下的圆柱壳轴对称弹塑性动屈曲问题。本构关系采用增量理论，借助增量数值方法求解动力方程组。研究不同边界条件对屈曲的影响，以及径向外压力在不同边界条件下对屈曲的影响。     

有限长圆柱壳中轴对称弹性瞬态波

有限长的计及剪切变形和转动惯性的弹性圆柱壳的轴对称运动方程经过Laplace变换后转化为一组相空间中的方程。对该方程组作了一些适当的处理后,应用广义射线法,得到了相空间中位移和内力的射线法表达式。采用快速Fourier变换作Laplacl逆变换,即可得到圆柱壳受轴对称冲击载荷时的弹性瞬态波解。     

Critical velocity of sandwich cylindrical shell under moving internal pressure

Critical velocity of an infinite long sandwich shell under moving internal pressure is studied using the sandwich shell theory and elastodynamics theory. Propagation of axisymmetric free harmonic waves in the sandwich shell is studied using the sandwich shell theory by considering compressibility and transverse shear deformation of the core, and transverse shear deformation of face sheets. Based on the elastodynamics theory, displacement components expanded by Legendre polynomials, and position-dependent elastic constants and densities are introduced into the equations of motion. Critical velocity is the minimum phase velocity on the desperation relation curve obtained by using the two methods. Numerical examples and the finite element （FE） simulations are presented. The results show that the two critical velocities agree well with each other, and two desperation relation curves agree well with each other when the wave number k is relatively small. However, two limit phase velocities approach to the shear wave velocities of the face sheet and the core respectively when k limits to infinite. The two methods are efficient in the investigation of wave propagation in a sandwich cylindrical shell when k is relatively small. The critical velocity predicted in the FE simulations agrees with theoretical prediction.