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1.
A postbuckling analysis is presented for a shear deformable anisotropic laminated cylindrical shell with stiffener of finite length subjected to axial compression. The material of each layer of the shell is assumed to be linearly elastic, anisotropic and fiber-reinforced. The governing equations are based on a higher order shear deformation shell theory with von Kármán-Donnell-type of kinematic nonlinearity and including the extension/twist, extension/flexural and flexural/twist couplings. The ‘smeared stiffener’ approach is adopted for the beam stiffeners. This arrangement allows the beam stiffeners to be assembled directly into the global stiffness matrix. The nonlinear prebuckling deformations and initial geometric imperfections of the shell are both taken into account. A singular perturbation technique is employed to determine the buckling loads and postbuckling equilibrium paths. The numerical illustrations concern the postbuckling response of perfect and imperfect, grid, axial, ring stiffened, and unstiffened shells. The results confirm that there exists a compressive stress along with an associate shear stress and twisting when the anisotropic shell is subjected to axial compression. The postbuckling equilibrium path is unstable for the moderately thick cylindrical shell under axial compression and the stiffened shell structure is imperfection-sensitive. 相似文献
2.
The dynamic torsional buckling and post-buckling of elasto-plastic circular cylindrical shell isstudied.By the usage of the Bodner-Partom constitutive relation,the present visco-plastic problem is treat-ed as an orthotropic elastic problem.Based on the nonlinear large deflection shell therory,the governingdynamic buckling equation is solved by the Runge-Kutta method,and the critical buckling stress is deter-mined by the B-R criterion.The present paper is mainly focused on the imperfection sensitivity,the strainrate sensitivity,and the dynamic post-buckling characters for the shell loaded dynamically with a constantshear strain rate.Numerical results show that the critical shear stress and imperfection sensitivity will in-crease with the increase of strain rate.It is found that the elastic buckling stress is more sensitive toimperfection than the visco-plastic buckling.The present research also reveals some dynamic post-bucklingcharacters for the cylindrical shell,and it is shown that the shell will vibra 相似文献
3.
环肋圆柱壳体在水下冲击波作用下的动力弹塑性屈曲 总被引：1，自引：0，他引：1
本文以加肋圆柱壳体为对象建立力学模型，在水下爆炸产生的冲击波作用下，考虑流体与结构的耦合效应，研究加肋圆柱壳体的弹塑性失稳变形量及动力响应特性。数值分析显示出的最终变形形状和压力变化过程与实验资料一致的 相似文献
4.
耐压舱设计是水下机器人的核心技术之一,其极限承载力研究是核心中的核心。针对球壳封盖加柱形壳体耐压舱,现行标准对于初始导入缺陷数值的确定往往过于保守,对于耐压舱体数量较多的无人潜水器来说,过大的设计质量是总体设计所无法接受的。首先采用装配体整体建模策略,建立复合屈曲的受力模型,将三大非线性影响因素同时引入到极限承载力研究中,提升了计算精度。然后分别针对确定性缺陷和非确定性缺陷结构开展极限承载力研究。最后,提出以0.23%的初始缺陷导入尺度作为球壳封盖加圆柱壳体的耐压壳体缺陷导入参数,给出了导入尺度的计算方法,并借助水压试验对上述参数的准确性进行验证。 相似文献
5.
Based on the finite displacement theory of elastic shells, the postbuckling behaviour of submarine pipelines with residual stresses is investigated by using a new finite element formula. The corresponding complementary energy functional is first constructed, and then a geometrical stiffness matrix suitable for the postbuckling of a cylindrical shell is derived. In this matrix the effects of initial stresses and harmonic coupling terms have been considered. The formulation presented in this paper can be used to solve a significant class of problems in the analysis of elastic shells. 相似文献
6.
Wang Deyu Chen Tieyun
Associate Professor Dept. of Naval Architecture Ocean Engineering Shanghai Jiaotong University Shanghai
Professor Dept. of Naval Architecture Ocean Engineering Shanghai Jiaotong University Shanghai 《中国海洋工程》1995,(1)
- The Bodner-Partom constitutive equation is used to study the viscoplastic torsional bucklingof perfect cylindrical shell. By treating the viscoplastic shell as an orthotropic shell at each moment and neglecting the inertia term, the critical torque is determined from a set of homogeneous linear equations. The strain rate sensitivity is mainly discussed in the present paper. 相似文献
7.
Luis A. Godoy 《Applied Ocean Research》1985,7(3):152-157
Forced vibrations of the walls of a vertical cylindrical shell under the impact of a breaking wave are studied theoretically. The wave action is modelled as a pressure distribution which varies in time and space. A linear dynamic analysis of the transient response is carried out by means of the modal superposition technique, in which the static stresses are considered. The results show that in thin shells, the transient displacements could be of the order of the thickness of the shell. It is suggested that these large displacements could play an important role in eroding the buckling capacity of the structural component. The problem of limiting the dynamic displacements is discussed by interaction diagrams for static axial load-dynamic lateral pressure, and by examination of the confluence of shell and wave parameters for which the transient displacements do not exceed a given value. 相似文献
8.
采用分枝定界法和序列二次规划方法,对载人潜水器圆柱形耐压壳体的重量最小化进行了研究.设计变量是壳板的厚度、肋骨的型号、间距和数量,讨论了下潜深度、材料几何参数对重量以及其它特征量的影响.算例计算表明,下潜深度越大,屈服极限越高的材料重量减轻越明显.对于大深度而言,选用高屈服极限材料,可以使得材料能够充分利用.文中还对结构重量占排水量比例随深度变化的情况进行了研究. 相似文献
9.
Acoustic radiation from a point driven, infinite, periodically ring-stiffened, laminated composite cylindrical shell submerged in flowing fluid is investigated theoretically. Both the effects of in-plane and out-of-plane vibrations of the ring-stiffeners and the effects of fluid convection on far field acoustic radiation behaviors are concerned. The equations of motion of the laminated composite cylindrical shell is presented on the basis of the first order shear deformation theory. Fourier transform and Poisson summation formula are used to transform the equations into a set of infinite algebraic equations expressed in the wavenumber domain. After truncation, the response of the laminated composite cylindrical shell is solved, and the stationary phase approximate is employed to find the expression for the far field sound pressure. Convergence analysis of the numerical solutions is conducted. The theoretical model and numerical method proposed in this paper are validated by comparison with those presented in available literature. Finally, numerical results are presented to demonstrate the effects of various parameters such as the size and spacing of the ring-stiffener, the thickness and the radius of the cylindrical shell, the lamination angle and the lamination scheme of the composite materials as well as the Mach number on the far field sound pressure. 相似文献
10.
基于振动的水下环肋圆柱壳临界载荷的预报具有结构无损的优势。以Flügge壳体理论和基于正交各向异性理论的环肋圆柱壳自由振动方程为基础,运用波传播法得出耦合系统的频率方程,并求出对应外压下的固有频率,通过最小二乘法线性拟合获得临界载荷、外压及固有频率的关系表达式。绘图得知任意边界的同一模态下,水下环肋圆柱壳的固有频率平方与静水压力成正比。结构失稳时,刚度丧失,固有频率降为零,据此求出水下环肋圆柱壳的最小弹性临界载荷。分析了不同边界条件对环肋圆柱壳临界载荷的影响,得知边界约束越强,环肋圆柱壳的临界载荷越大。结果对比表明了本方法的正确性,为水下环肋圆柱壳的固有频率及临界载荷的理论计算提供了一种新的方法。 相似文献
11.
- The dynamic buckling of elasto-plastic cylindrical shells under axial fluid-solid impact is investigated theoretically. A simplified liquid- gas- structure model is given to approximately imitate the problem. The basic equation of the structure is derived from a minimum principle in dynamics of elasto-plastic continua at finite deformation, and the flow theory of plasticity is employed. The liquid is incompressible and the gas is compressed adiabatically. A number of numerical results are presented and the characteristics of the buckling behavior under fluid-solid impact are illustrated. 相似文献
12.
In this study,an FEM-SBFEM(scaled boundary finite element method)coupling procedure proposed by Fan et al.(2005)is adopted to obtain the dynamic responses of a submerged cylindrical shell subjected to plane step or exponential acoustic shock waves.The coupling procedure can readily be applied to three-dimensional problem,however for clarity,the problems to be presented are limited to two-dimensional domain.In the analyses,the cylindrical shell is modeled by simple beam elements(using FEM),while the effects of the surrounding infinite fluid is modeled by the SBFEM.In it,no free surface and seabed are involved.Compared with Fan and his co-authors' works,the FEM-SBFEM coupling procedure is further verified to be feasible for shock waves by benchmark examples.Furthermore,parametric studies are performed and presented to gain insight into effects of the geometric and material properties of the cylindrical shell on its dynamic responses. 相似文献
13.
本文研究了加强柱形壳体在风型载荷作用下的静力屈曲特性。由于前屈曲薄膜应力状态是非均匀的应力场，因而使问题求解的难度增加。本文应用能量近似法，求解带环肋加筋的柱形壳体的整体稳定性。 相似文献
14.
周向变刚度环肋圆柱壳应力分析研究 总被引：1，自引：0，他引：1
采用大曲率梁理论和弹性基础梁带理论,建立潜艇特殊舱段结构的力学模型。利用能量法求出肋位处耐压船体壳板中面周向应力。建立环肋圆柱壳微分方程并根据边界条件求解,得到周向变刚度环肋圆柱壳应力计算方法。通过理论分析和模型试验验证了本计算方法。 相似文献
15.
TANG Wenyong ZHANG Shengkun CHEN Tieyun Doctor School of Naval Architecture Ocean Engineering Shanghai Jiaotong University 《中国海洋工程》1998,(3)
This paper analyzes the dynamic structure-fluid interaction response of a submerged compo-site cylindrical shell.Dynamic equations based on the first-order shear deformation theory include the ini-tial stresses and structure-fluid interaction forces due to fluid.The field equation is solved by expandingthe velocity potential into series similar to transverse deflection of the cylindrical shell and thestructure-fluid interaction force is obtained.The dynamic response is investigated by means of series expan-sion method.The effects of structure-fluid interaction on dynamic response are discussed. 相似文献
16.
This study investigated the linear and nonlinear dynamic responses of three cylindrical shell structures subjected to underwater small charge explosions in a 4 m×4 m×4 m water tank. The dimensions of the cylindrical shell structures were 90 cm×30 cm×1 mm (length×diameter×thickness). Both ends of the cylindrical shell were mounted with thick plates to provide support and create an enclosed space. The three cylindrical shell structures were un-stiffened, internally stiffened and externally stiffened, respectively. The experiments involving the dynamic response of cylinders subjected to underwater explosion (UNDEX) were performed under different standoff distances, varying from 210 to 35 cm. A small quantity of explosives was used to generate the shock loading. The plastic deformation of the cylindrical shell was observed at a standoff distance of less than 50 cm. Other conditions were tested to examine cylinder linear response. Dynamic analyses were performed for the experimental model using FEM and compared with the test results. The accelerations and dynamic strains of cylindrical shells obtained from the experiment were compared with those obtained by FE analysis. Finally, problems related to small-scale UNDEX experiments performed in small water tanks were analyzed. 相似文献
17.
18.
Static analysis of stiffened shells has been carried out using an eight-noded isoparametric element for the shell and a three-noded curved beam element for the stiffener. A same displacement function is used for the shell and the stiffener elements. A modified technique has been followed to analyse the shell, which is an improvement over the degenerated shell concept. The stiffness matrix of the curved beam element is generated irrespective of its position and orientation within the shell element. The stiffness matrix of the stiffener is then transferred to all the nodes of the shell element. Numerical examples of stiffened shells with concentric and eccentric stiffeners have been analysed and the results presented together with those available in published literature. 相似文献
19.
基于ABAQUS的海底管道静水压溃压力的敏感性分析 总被引：1，自引：0，他引：1
局部屈曲压溃是海底管道发生稳定性破坏的一种形式,随着管道的刚度相对越来越柔,厚度相对越来越薄,管道发生屈曲压溃的问题也越来越突出。运用ABAQUS有限元分析软件进行管道的非线性屈曲分析,确定不同径厚比、初始椭圆度、轴向拉力和弯矩作用下的管道静水压溃压力,以分析静水压溃压力对这些因素的敏感性。 相似文献
20.
不规则物体体积测量的传统方法有排液法、称重法和排气法等,不仅操作繁琐,而且准确度及精确度低。本文首次提出了排水称重法,利用该方法能够更加简单、快速、准确地测量出物体的体积和质量。用此法对不同海区26个采样点的1100个牡蛎贝壳密度进行了测定分析,结果表明:大部分牡蛎的左壳密度显著小于右壳密度(P0.05);对于不同海区间的牡蛎,贝壳密度存在极显著的差异(P0.001);分布海区相近的牡蛎间,壳的密度也趋于相近;受环境压力相对较大的潮间带上部的牡蛎,贝壳密度也相对较大。本研究为剖析牡蛎贝壳形成机制以及温度、盐度和海洋酸化等环境因素对牡蛎贝壳形成的影响等研究提供了实验数据和参考。 相似文献