Effect prediction of stiffened-ring cylindrical shells subjected to drop mass impact

This study focuses on the effect of lateral mass impact on ring-stiffened thin-walled cylindrical shell.Cylindrical shells were fabricated to validate the numerical modeling and analytical techniques,and drop tests were performed using a rigid spherical indenter.Next,stiffened-ring cylindrical shells with various structural size parameters were simulated using ABAQUS software.The relationships between the impact force,deformation displacement,and rebound velocity were established,on the basis of impact mechanics theory and simulation results.It derived fitting functions to analyse the relationship between the maximum load and maximum displacement of ring-stiffened cylindrical shell under dynamic mass impact.Based on the validation of the simulation model,the fitting function data were compared with the simulation results,and the functions showed a good accuracy.Besides,the parameters,mass ratio and stiffened-ring mass ratio were used to reflect the effect of the mass change in the ring-stiffened cylindrical shell.Furthermore,parametric studies on ring-stiffened cylindrical shell models were conducted to analyse the progressive impact responses.

ANALYSIS OF SOUND RADIATION FROM THE RING-STIFFENED CYLINDRICAL SHELL COATED WITH VISCOELASTIC LAYER IN FLUID MEDIUM

The Donnell theory of shell is applied to describe shell motion and layer motion is described by means of three-dimensional Navier equations.Using deformation harmonious condi- tions of the interface,the effects of stiffeners and layer are treated as reverse forces and moments acting on the cylindrical shell.In studying the acoustic field produced by vibration of the sub- merged ring-stiffened cylindrical coated shell,the structure dynamic equation,Helmholtz equation in the fluid field and the continuous conditions of the fluid-structure interface compose the cou- pling vibration equation of the sound-fluid-structure.The extract of sound pressure comes down to the extract of coupling vibration equation.By use of the solution of the equation,the influ- ences of hydrostatic pressure,physical characters and geometric parameters of the layer on sound radiation are discussed.

Stability characteristics of ring-stiffened cylindrical shells under different longitudinal and transverse external pressures

Because ring-stiffened cylindrical shell structures have many merits, they are widely used in many areas. However, as the strength of steel increase continuously, ensuring of the structure stability is becoming more and more important. Therefore, it is necessary to carry on a more particular analysis. Based on the understanding and analysis of the characteristics of stability for a ring-stiffened cylindrical shell under uniform external pressure and under external single pressure, the characteristics under different cross uniform external pressures are analyzed, and the regularity of it is also gotten. The curve of stability given various geometrical parameters under different cross uniform external pressures is protracted by the analysis of the theory. The conclusion not only improves the theory structural mechanics, it also was important effects on engineering calculation and design.

DYNAMIC BUCKLING OF STATICALLY PRELOADED RING-STIFFENED CYLINDRICAL SHELLS UNDER AXIAL FLUID-SOLID IMPACT LOADING

The Initial Imperfection Amplified Criterion is applied toinvestigate the geometric nonlinear dynamic buckling of staticallypreloaded ring-stiffened cylindrical shells under axial fluid-solidimpact. Tak- ing account of the effects of large deformation andinitial geometric imperfection, the governing equations are obtainedby the Galerkin method and solved by the Runge-Kutta method. Theeffects of static preloading (uniform external radial pressure) onthe buckling features and the load-carrying ability of ring-stiffenedcy- lindrical shells against axial impact are discussed.

ANALYTICAL SOLUTION OF RADIATED SOUND PRESSURE OF RING－STIFFENED CYLINDRICAL SHELLS IN FLUID MEDIUM

In this paper, analytical formularions of radiated sound pressure of ring-stiffenedcylindrical shells in fluid medium are derived by means of Hamilton's principleHuygens principle and Green function . These formulations Can be used to compute the sound pressure of the shell's surface nearfield and farfield.

深海无人系统大长径比环肋圆柱壳结构设计与试验研究

环肋圆柱壳是深海无人系统广泛采用的一种耐压结构形式,保障其结构安全是系统研制过程中非常重要的一环。针对环肋圆柱壳的结构特征推导了组合结构重量关系式和结构参数简化估算方法,并以一种超长型深海无人系统耐压结构为例,围绕大长径比环肋圆柱壳的结构形式、设计计算、仿真分析、模型验证等开展研究。研究表明提出的大长径比环肋圆柱壳结构设计参数简化估算方法具有较好的适应性。相关计算和分析结果可以为该型深海无人系统结构设计提供技术支撑,也可以为其他类似耐压结构设计提供参考。

基于塑性弦线法的深水爆炸下加筋锥柱壳变形模型

为探究凸型加筋锥柱壳在静水压与深水爆炸载荷联合作用下的动态响应,在塑性弦线模型基础上考虑静水压载荷、锥角因素,将问题简化为求解拥有初边界值的波动方程,利用特征值展开将肋间板壳径向位移表示为无穷级数的形式,并对每个特征值计算相应的卸载时间,以此显示冲击波载荷的衰减特性。使用有限元程序Abaqus对半锥角为20°的凸型加筋锥柱壳开展最大深度500 m、最大冲击因子0.79 kg 0.5/m的水下爆炸数值模拟研究,对邻近结合处的柱段、锥段肋间板壳的理论模型计算结果进行验证对比和讨论。研究结果表明:与不计静水压相比,静水压使得肋间板壳刚度减小——最大位移出现时刻延滞,最终径向位移随水深而增大;在不同冲击因子下,理论模型与数值模拟最终径向位移误差最大为21.7%(锥段),最小为2.0%(柱段);由于锥角的存在,肋间板壳位移不再关于中心点对称分布,中心点最终位移较柱段减小40%以上。

基于ALE方法的加筋圆柱壳水下接触爆炸计算研究

随着水下制导技术的发展,接触爆炸对水下结构的毁伤问题越加受到关注。为研究加筋圆柱壳结构水下接触爆炸毁伤特性,采用LS-DYNA软件的任意拉格朗日-欧拉(ALE)方法模拟爆炸冲击波的形成、传播及其对圆柱壳结构的毁伤过程,探讨水下接触爆炸作用下单、双层加筋圆柱壳的毁伤响应特性,并分析不同药量和爆距条件下加筋圆柱壳的破坏模式。研究结果表明:在不同药量和爆距的水下接触爆炸条件下,加筋圆柱壳呈现多种破坏模式,加筋和加肋位置处易出现撕裂状破口,板壳结构的破坏主要表现为凹陷变形及沿着加筋位置处扩展的裂纹,其中爆距对破坏模式的影响更明显。本文结果可为水下接触爆炸冲击波作用下水下航行体结构强度分析和防护设计提供参考。

VIBRATION AND STABILITY OF RING-STIFFENED THIN-WALLED CYLINDRICAL SHELLS CONVEYING FLUID

Based on the Fliigge shell theory, equations of motion of ring-stiffened thin-walled cylindrical shells conveying fluid are developed with the aid of the Hamilton＇s principle. Analysis is carried out on the vibration and stability of the ring-stiffened shells conveying fluid, and the effects of fluid velocity, the Young modulus, the size, and the number of the ring stiffeners on the natural frequency and the instability characteristics are examined. It is found that stiffeners can reduce the number of circumferential waves for the fundamental mode, and increase the shell＇s natural frequency, and thus the critical fluid velocity. For the number of longitudinal half waves being equal to one, the natural frequency and the corresponding critical fluid velocity are the largest for the internal-ring stiffened shell and are the smallest for the symmetrical-ring stiffened shell. The natural frequencies and the corresponding critical fluid velocity predicted by the established model increase with the increase in the Young modulus, the size, or the number of the stiffeners.

Nonlinear Buckling Analysis of Pre-stressed Ring-Stiffened Circular Cylindrical Shells Under External Pressure

This paper is concerned with the nonlinear buckling behavior of pre-stressed ring-stiffened thin circular cylindrical shells under external pressure.According to the geometrical nonlinearity,governing equations are derived by incorporating initial stresses based on Donnell-type shell theory.The "smeared stiffeners" approach is used for ring stiffeners.The numerical analyses are conducted by Gelerkin's method to obtain critical buckling loads of shells.This study shows effects of initial stresses on stability of shells.Moreover,effects of initial stresses on buckling modes of shells are discussed.

凸型加筋锥柱结合壳深水爆炸失稳特性研究

为研究凸型加筋锥柱结合壳结构在深水爆炸载荷作用下的动力学响应以及在此过程中伴随的失稳特性,采用ABAQUS有限元软件中的声固耦合算法开展了300~500 m水深条件下深水爆炸数值模拟研究,基于结构挠度变化的失稳判据,分析总结了加筋锥柱结合壳的失稳模式,获得了加筋锥柱结合壳临界失稳载荷和临界失稳挠度随水深和壳体结构参数的变化规律.结果表明,水深条件、壳体半径、壳体厚度以及结构锥角对结构稳定性有较大影响,而腹板厚度对结构的稳定性影响不大.在此基础上,运用量纲分析的方法结合模拟得到的临界失稳数据建立了结构在常见失稳模式下结构临界失稳判据的计算公式.

环形加筋圆柱壳的焊接残余应力及振动特性研究

[目的]旨在评估环形加筋圆柱壳的复杂焊接残余应力及其对结构振动特性的影响等。[方法]首先,采用二氧化碳气保焊实现环形加筋圆柱壳的焊接,使用非破坏性的X(XRD)测量关键区域焊接后以及退火热处理后的焊接纵向残余应力。其次,通过高效的热−弹−塑性有限元计算,分析焊接过程中的温度场和残余应力,并研究移动体热源和固定热源模型对焊接模拟结果的影响。最后,在自由状态下测试环形加筋圆柱壳焊接后以及退火热处理后的结构振动特性,并通过有限元法预测结构振动模态及其固有频率。[结果]基于试验测量、焊接热−弹−塑性以及结构模态有限元计算,得到了环形加筋圆柱壳热处理前后的残余应力和振动特性。[结论]固定热源模型可以高效地预测环形加筋圆柱壳的热力学响应,预测的焊接残余应力与测量结果基本一致;退火热处理工艺可以有效消除焊接残余拉应力,且焊接残余应力对环形加筋圆柱壳的振动特性影响甚微。

环向加筋夹层圆柱壳体应力计算方法

针对环向加筋夹层圆柱壳体的应力计算问题,本文提出内、外壳板纵向力计算模型,建立了环向加筋夹层圆柱壳体在外压载荷作用下的应力解析计算方法,计算结果与有限元结果吻合较好;以10%误差(解析应力值与有限元值的偏差)为衡准,初步提出该方法的适用条件;同时系统探究了各形状参数对环向加筋夹层圆柱壳体关键位置应力的影响规律。为超大潜深新型耐压结构设计提供理论基础。

大厚度环肋圆柱壳结构应力特性研究

环肋圆柱壳是水下工程产品中广泛采用的一种典型耐压结构。随着工作深度需求越来越深,环肋圆柱壳结构设计逐渐呈现出大厚度的新结构特征。本文以某深海无人系统耐压结构参数为例,采用理论方法和有限元仿真方法进行计算分析,研究不同厚度特征参数(t/R)下的环肋圆柱壳结构应力特性。结果表明,基于薄壳理论的解析计算方法不适用于大厚度环肋圆柱壳结构应力计算,大厚度环肋圆柱壳结构的应力特性与传统圆柱壳结构存在较大差异,在大厚度环肋圆柱壳结构设计时应综合权衡其壳板应力和肋骨应力的特性。

基于幂级数法的环肋圆锥壳振动特性分析

[目的]旨在利用解析法求解环肋圆锥壳的振动方程,对环肋圆锥壳的振动特性进行理论研究。[方法]首先,对圆锥壳分段处理,将圆锥壳沿母线方向、环向和法向的位移分别写成幂级数解的形式,并推导出幂级数项前系数的递推关系式;然后,采用梁模型模拟不同环肋数对圆锥壳振动响应特性的影响;接着,将圆锥壳分段及其环肋边界条件、位移和内力矩阵进行组装求解,得到在外部简谐力激励下圆锥壳的振动响应特性,并将所得结果与ANSYS有限元数值方法的计算结果进行对比,验证所提计算方法的有效性。最后,运用所提理论方法进行环肋圆锥壳的振动特性分析。[结果]结果显示,圆锥壳安装的环肋可明显抑制圆锥壳的振动,具体表现为响应幅值降低、固有频率升高,且在相同频段内共振峰数量减小;增大壳体厚度会引起壳体振动响应幅值降低以及固有频率升高;此外,增大半锥角、轴线长度和环肋数均可降低环肋圆锥壳的振动响应幅值。[结论]研究表明,所用方法对环肋圆锥壳振动的理论研究具有一定意义。

大厚度环肋圆柱壳三维应力分析方法研究

随着深海应用需求的不断发展,水下工程产品的耐压环肋圆柱壳结构呈现出大深度大厚度的新型结构特点。相比于传统意义的环肋圆柱壳,应力分析一般将其简化为二维应力状态,大厚度环肋圆柱壳的应力强度应进行三维应力分析。本文通过肋骨作用力函数等效假设,将环肋圆柱壳分解为圆柱壳梁环、肋骨腹板圆环和肋骨面板圆环组成的简化力学模型,基于弹性力学平面问题分析方法,提出一种大厚度环肋圆柱壳的三维应力分析方法,给出环肋圆柱壳的典型应力计算式。算例分析表明,本文方法计算值与数值仿真计算结果基本一致,具有较好的工程应用精度。

基于遗传算法的环肋圆柱壳结构优化设计

本文对某潜器的环肋圆柱耐压壳结构开展以减重为目标的优化设计,通过使用遗传优化算法,以环肋圆柱壳结构中的肋骨尺寸、肋骨间距及壳体厚度作为优化设计变量,在强度和稳定性满足的约束条件下,得出优化后重量较轻的设计方案,同时结合理论和数值方法校核该方案下强度和稳定性,以验证方案有效性。研究结果表明,优化后理论与数值计算得出强度与稳定性符合规范要求,优化后环肋圆柱壳结构重量得到有效降低,该研究方法可为今后类似结构物优化设计提供参考。

环肋柱壳振动和声辐射试验分析

对环肋光壳和外表敷设粘弹性阻尼材料的环肋柱壳进行了振动和声辐射试验 ,测量了壳体的固有频率和辐射声压 ,并与理论计算值做了对比 ,结果发现环肋光壳比敷设阻尼材料的环肋柱壳的同阶固有频率高 ,壳体外表面敷设阻尼材料后 ,在相同的激励下其辐射声压级普遍降低 ,降低的幅值大小与激励的频率和辐射的方向有关 ,表明本文的计算方法是可信的 。

考虑筋/板相互作用的环肋圆柱壳屈曲强度分析

环肋圆柱壳是潜艇耐压壳体的一种主要结构形式。环肋圆柱壳的失稳破坏主要表现在肋骨间的壳板失稳和总体失稳。在计算肋骨间的壳板失稳时,传统方法认为肋骨为壳板提供简支边界,忽略了在边界上肋骨和壳板的相互影响。在实际结构中,由于肋骨提供扭转刚度,壳板在与肋骨相交的边界上将存在弯矩,并非自由支持边界。因而,壳板失稳时,筋/板产生相互影响,提高了壳板的屈曲强度。本文的主要目的是,推导考虑筋/板相互影响的环肋圆柱壳壳板屈曲强度的理论计算方法,分析筋/板的相互关系。通过本文的算例表明,本文推导的计算方法以及所编制的计算程序是可靠的,可以用于工程设计。

基于ANSYS的外压圆柱壳的屈曲分析

圆柱壳的稳定性是外压容器设计中应该考虑的首要问题。文章利用有限元软件ANSYS分别对外压圆柱壳进行了特征值、几何非线性和几何/材料双非线性屈曲分析,并把有限元计算结果和Mises公式计算结果进行了对比,给出了外压圆柱壳稳定性的分析结论。同时,对带加强圈的外压圆柱壳进行了失稳分析,提出了一种判断加强圈的刚度是否满足稳定性要求的新方法。