一种分析受爆炸冲击的水下圆柱壳结构强度的方法

根据小型水下圆柱壳状结构受爆炸冲击后散射现象严重的特点，提出一种新的冲击载荷的近似计算方法。首先把带加强筋的实际柱壳状结构简化为与实际结构外形尺寸和低阶振动模态都相同的理想柱壳，并将冲击波分解为不同频率谐和平面波的迭加，然后，采用耦合模态法分析受爆炸冲击水下圆柱壳状结构周围的散射场，求出圆柱壳状水下结构的表面总压，再通过积分求得表面平均总压，并探讨结构的弹性变形、材料特性对它的影响，最后用有限元软件分析某水下工程实际结构受到爆炸冲击后的弹塑性变形时间历程。结果表明，结构的弹塑性变形的时间历程明显落后于表面平均总压的时间历程，即前者的峰值到达时间迟于后者的峰值。工程实例分析的结果表明，本文方法具有物理概念清晰，运用方便，准确度较高的特点，可适用于水下圆柱壳状结构受到冲击后的强度分析。     

工装约束下火箭舱段壳体的结构振动特性研究

将地面试验中卡环工装对舱段壳的影响转化为弹性边界条件下圆柱壳耦合结构的振动问题,通过卡环工装与圆柱壳接触建模计算得到工装作用于舱段壳的法向约束刚度,并采用增补函数的方法构建了工装约束边界条件下圆柱壳耦合结构的振动理论分析模型。结果表明：本研究模型能够反映卡环工装对于舱段壳振动特性的影响,理论计算结果与试验测试结果的变化趋势基本一致;在卡环工装的约束下,舱段壳的低频振动受到显著抑制,工装的约束刚度及其在舱段壳上的夹持位置对于舱段壳振动特性具有较大影响。     

水下无人航行器壳体抗毁伤性能的数值仿真研究

应用ABAQUS通用有限元软件中的声固耦合算法,对水下无人航行器壳体在远场水下爆炸冲击波作用下的抗毁伤性能进行了数值仿真研究。在数值仿真中,计算出在三硝基甲苯炸药爆炸时,不同方向及爆距条件下航行器壳体结构的动态响应过程,确认了航行器壳体的易损舱段及位置,得出抗爆炸毁伤的安全距离,为水下无人航行器的结构设计和抗毁伤性能指标考核提供了参考。     

内部爆炸加载条件下圆柱钢壳的动态断裂

在内部爆炸冲击波载荷作用下,爆炸容器的动态断裂是进行爆炸容器安全评估和失效分析的基础。为了研究爆炸容器的动态断裂特征,进行圆柱钢壳在中心装药的爆炸加载实验,采用非线性动力有限元分析程序LS-DYNA分析圆柱钢壳的弹塑性动力响应,研究圆柱钢壳的宏观变形和断口的宏观、细观形貌,分析圆柱钢壳的断裂模式及断裂机理。结果表明,圆柱钢壳纵向断口具有微孔聚集型剪切韧窝断裂特征,呈现出微孔聚集型剪切韧性断裂模式。内部爆炸冲击波加载下圆柱钢壳因径向膨胀发生动态塑性变形,产生剪切带,由于剪切带的软化效应而成为优先断裂通道,剪切带和环向拉应力的共同作用是形成微孔聚集型剪切韧窝断裂这种混合韧性断裂模式的原因。     

KM6载人宇宙飞船试验舱有限元分析

KM6载人宇宙飞船整体试验舱是由四个椭球壳、两个带筋圆柱壳、一个锥壳和三组大型法兰组成的复杂大型真空容器,它分为主舱和辅舱。这里采用有限元法对辅舱进行了强度、刚度和屈曲分析,并提出了改进方法,为设计人员直接采用,该试验已通过压力试验,实验证明了给出的结果的正确性。     

水下弹性圆柱壳结构声辐射有源控制研究

研究了利用次级环带声源对水下有限长弹性圆柱壳结构振动声辐射进行有源控制。给出了初级圆柱和次级环带声源之间的互辐射阻抗计算公式,考虑流固耦合效应,利用二次最优理论,以辐射声功率最小化为目标函数,得到次级环带声源的最优激励力,最后计算控制前后远场辐射声压的空间分布。结果表明:利用次级环带声源可以对弹性圆柱壳结构振动辐射噪声进行控制,增大次级环带声源与初级圆柱壳间距,控制效果变差;次级激励力位置对辐射声功率控制效果也会产生影响。     

水下弹性圆柱壳结构声辐射有源控制研究

研究了利用次级环带声源对水下有限长弹性圆柱壳结构振动声辐射进行有源控制。给出了初级圆柱和次级环带声源之间的互辐射阻抗计算公式,考虑流固耦合效应,利用二次最优理论,以辐射声功率最小化为目标函数,得到次级环带声源的最优激励力,最后计算控制前后远场辐射声压的空间分布。结果表明:利用次级环带声源可以对弹性圆柱壳结构振动辐射噪声进行控制,增大次级环带声源与初级圆柱壳间距,控制效果变差;次级激励力位置对辐射声功率控制效果也会产生影响。     

基于SPH算法的驾驶室底部结构对爆炸冲击波响应数值仿真

针对地雷等简易爆炸装置在车辆驾驶室底部非接触爆炸问题,引入无网格光滑粒子流体动力学(Smoothed particle hydrodynamics,SPH)算法模拟爆炸冲击波作用下车辆底部结构的响应。以四边约束靶板为研究对象,分析靶板在爆炸冲击下的能量、应力变化和破坏形态,通过与传统的任意拉格朗日欧拉(Arbitrary Lagrangian-Eulerian,ALE)固流耦合分析法和经验公式计算结果对比,验证SPH算法应用于处理此类问题的可行性;利用SPH算法对爆炸冲击波作用下驾驶室底部结构进行数值仿真,分析车辆底部的油箱、电瓶支架、驾驶室地板、车架等关键结构的冲击响应,并与试验做出对比验证。仿真结果表明,基于SPH算法的爆炸仿真分析具有精度较高、建模简单、耗费计算资源少等优势,能够应用于爆炸冲击波作用下驾驶室底部板壳结构的响应研究,并为驾驶室底部结构抗爆炸设计提供参考。     

基于小波变换的水下爆炸压力时频特征分析

提出了水下爆炸压力时频特征分析原理,给出了一次水下爆炸压力的测试结果,分析了短时非平稳水下爆炸压力的时频特征,提取了冲击波、首次和二次气泡脉动压力信号,讨论了它们在不同频带的能量分布规律.研究结果表明,冲击波压力的峰值大,衰减快,主要作用在1 kHz以上的高频段,易造成舰船局部的破损;气泡脉动压力的能量接近总能量的一半,主要作用在1 kHz以下中低频段,是使安装频率为数十赫兹的舰船设备产生冲击振动的主要能源.     

多层内凹蜂窝圆柱壳冲击动力学行为分析

构建了不同角度单层内凹蜂窝圆柱壳模型，提出了一种新型多层复合内凹蜂窝圆柱壳结构。利用有限元仿真方法研究了单层和多层内凹蜂窝圆柱壳在轴向冲击下的变形行为，分析对比了单层和多层内凹蜂窝圆柱壳在不同冲击速度下的平台应力和比吸能特性。结果表明，在相同密度和尺寸下，多层内凹蜂窝圆柱壳的冲击能量吸收能力相对于单层内凹蜂窝圆柱壳有显著提升；内凹蜂窝圆柱壳初始变形破坏位置随着冲击速度的改变而改变；多层内凹蜂窝圆柱壳没有表现出负泊松比性质。     

Postbuckling of shear deformable FGM cylindrical shells surrounded by an elastic medium

This paper presents a study on the postbuckling response of a shear deformable functionally graded cylindrical shell of finite length embedded in a large outer elastic medium and subjected to axial compressive loads in thermal environments. The surrounding elastic medium is modeled as a tensionless Pasternak foundation that reacts in compression only. The postbuckling analysis is based on a higher order shear deformation shell theory with von Kármán-Donnell-type of kinematic nonlinearity. The thermal effects due to heat conduction are also included and the material properties of functionally graded materials (FGMs) are assumed to be temperature-dependent. The nonlinear prebuckling deformations and the initial geometric imperfections of the shell are both taken into account. A singular perturbation technique is employed to determine the postbuckling response of the shells and an iterative scheme is developed to obtain numerical results without using any assumption on the shape of the contact region between the shell and the elastic medium. Numerical solutions are presented in tabular and graphical forms to study the postbuckling behavior of FGM shells surrounded by an elastic medium of tensionless Pasternak foundation, from which the postbuckling results for FGM shells with conventional elastic foundations are also obtained for comparison purposes. The results reveal that the unilateral constraint has a significant effect on the postbuckling responses of shells subjected to axial compression in thermal environments when the foundation stiffness is sufficiently large.     

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.     

水下爆炸冲击波作用下潜艇壳体动态响应的数值模拟

应用有限元软件MSC-Dytran对水下爆炸冲击波作用下潜艇壳体的动态响应进行模拟。模拟过程中在设置相同的爆炸环境下,建立了实体单元与面单元两种不同的潜艇壳体有限元模型,分别进行数值模拟。两种情况下的数值模拟均得到了与实际爆炸情况相符合的计算结果,得到了潜艇壳体主要迎爆位置处的压力和位移随时间的变化情况,并把两种模拟结果进行了比较,提出了两种模拟方法各自适合的应用条件。     

On the dynamic response of buried orthotropic cylindrical shells under moving load

This paper deals with the dynamic response of a buried orthotropic infinite cylindrical shell subjected to a radial line load moving along the shell axis. A thin shell theory formulation has been used and only axisymmetric response has been investigated. The shell is assumed to be perfectly bonded to the surrounding medium (soil) of infinite extent. Orthotropy parameters of the shell have been varied over a wide range to bring out their effects on the shell response. Results have been obtained for different soil conditions—hard, medium and soft.     

加肋圆柱形壳体的强度和稳定性计算方法

加肋圆柱形壳体被广泛应用于各领域中,当前发展热门的水下机器人就是采用这种结构型式。给出了壳体强度和稳定性的计算方法,并以某加肋薄壁结构为例,确定了该壳体结构的主要几何参数。     

一种水下灵巧手指端力传感器的研究

采用水压力补偿技术，设计了基于圆筒式测力结构的水下灵巧手指端力传感器，分析了其工作原理。采用有限元法计算了圆筒式测力结构的应变分布，验证该结构的合理性，由此推导出测量原理方程。采用有限元法对模型进行模态分析，确定了传感器的工作带宽。在陆上对传感器进行标定实验，根据实验数据计算出标定矩阵。性能测试结果显示，在陆上和浅水环境中测量结果一致，验证了该传感器在陆上标定是可行的。该传感器可用于水下，且测试精度满足目前水下灵巧手研究的要求。     

On the creep buckling of a long cylindrical shell

The advantages and limitations of a perturbation method of analysis for the creep buckling of shells is explored in this note by examining the particular case of a long cylindrical shell subjected to a uniform external pressure. It turns out that the oval deformation mode is the most critical as assumed in previous theoretical investigations. However, other modes can make important contributions to the deformation of a cylindrical shell and can, in fact, dominate the response if important imperfections are present in these harmonics.     

Postbuckling of shear deformable cross-ply laminated cylindrical shells under combined external pressure and axial compression

A postbuckling analysis is presented for a shear deformable cross-ply laminated cylindrical shell of finite length subjected to combined loading of external pressure and axial compression. The governing equations are based on Reddy's higher order shear deformation shell theory with von Kármán–Donnell type of kinematic nonlinearity. The nonlinear prebuckling deformations and initial geometric imperfections of the shell are both taken into account. A boundary layer theory of shell buckling, which includes the effects of nonlinear prebuckling deformations, large deflections in the postbuckling range, and initial geometric imperfections of the shell, is extended to the case of shear deformable laminated cylindrical shells under combined loading cases. A singular perturbation technique is employed to determine interactive buckling loads and postbuckling equilibrium paths. The numerical illustrations concern the postbuckling response of perfect and imperfect, unstiffened or stiffened, moderately thick, antisymmetric and symmetric cross-ply laminated cylindrical shells for different values of load-proportional parameters.