固支方板对水中爆炸作用的动态响应研究

 分析研究了在装药水中爆炸产生的强冲击载荷作用下固支方板的塑性动力响应过程。通过对水中爆炸理论和板的大变形理论分析，应用能量原理和Lagrangian函数，推导出反映固支方板在冲击载荷作用下变形的最终挠度的解析解。水中爆炸对固边方板破坏的实验在自制的水箱中进行。对不同的装药重量和炸距情况下方板的变形情况进行了理论计算，并对实验结果和误差来源进行了分析。实验结果和理论结果具有较好的一致性。     

轴向载荷下功能梯度材料Timoshenko梁动力屈曲分析

假设功能梯度材料Timoshenko梁各项物性参数只沿厚度方向按幂函数进行连续变化,研究了功能梯度材料Timoshenko梁的动力屈曲。基于一阶剪切理论,采用Hamilton原理推导出轴向载荷作用下,功能梯度材料Timoshenko梁动力屈曲的控制方程。利用里兹法与棣莫弗公式相结合,获得了功能梯度材料Timoshenko梁在夹支-固支边界条件下动力屈曲临界载荷的解析表达式和屈曲解。应用MATLAB编程计算,讨论了功能梯度材料Timoshenko梁的几何尺寸、梯度指数、模态数、材料构成、泊松比以及弹性模量对临界载荷的影响。结果表明:功能梯度材料Timoshenko梁动力屈曲临界载荷随梁长度的增大而减小,随着梯度指数的增大而减小,随模态数的增大而增大,说明冲击载荷越大,高阶模态越容易被激发;随着泊松比和弹性模量的增大而增大,且泊松比的影响较小,而弹性模量的影响较大。由于剪切项的影响,临界载荷-临界长度的关系曲线在加载端变化趋势平缓。随着模态数的增大,梁的屈曲模态越为复杂。     

超高速碎片云撞击下薄板变形与撕裂建模研究

为研究多层板结构中薄板在碎片云作用下的变形与破坏问题,开展了超高速撞击多层板实验。实验结果表明,薄板在高速碎片云冲击下的典型破坏特征为中央穿孔及环孔凹陷变形与花瓣型撕裂。在此基础上,考虑弯矩和膜力作用,建立了描述薄板在轴对称分布强冲击载荷作用下大变形的理想刚塑性环板模型,据此可以计算环板变形过程的横向与径向速度场,结合Grady破碎理论,可以计算花瓣型撕裂的花瓣数,理论计算值与实验比较吻合。研究结果可以为多层板结构在超高速弹丸撞击下的毁伤评估提供理论基础。     

射弹冲击下带预裂槽金属靶的防护性能研究（英文）

采用弹道实验和数值模拟的方法研究了带环形预裂槽的金属靶在射弹冲击下的毁伤模式和防护性能,分析了弹头形状、预裂槽直径及深度等因素对靶板防护性能的影响。结果表明:对带有环形预裂槽的金属靶板,存在两种主要毁伤模式,即环形槽内部的侵彻和环形槽底的冲击断裂;临界毁伤速度与毁伤模式密切相关,随着环形槽深度的增大或半径的变小,临界毁伤速度变小;与尖头弹相比,平头弹的临界毁伤速度更小;微观分析表明,在射弹冲击作用下,环形槽底部产生绝热剪切带,更容易形成充塞剪切破坏。     

基于Galerkin法研究应力波作用下复合材料板的动力学失稳

基于Kirchhoff薄板理论和Hamilton原理,考虑应力波效应,对含初始几何缺陷的三边简支、一边固支的复合材料板,建立了振动控制方程,得到了其屈曲临界荷载表达式。采用MATLAB编程进行数值计算,讨论了初始几何缺陷、初相位、铺层角度、屈曲模态阶数及铺层层数对板屈曲临界荷载的影响。结果表明:复合材料板的屈曲临界载荷随临界长度增大、铺设厚度减小、初始几何缺陷系数增大、振型函数初相位减小而减小。此外,复合材料板的各层铺层角度与荷载作用方向的夹角越小,屈曲临界载荷越大,当板的对称铺设层数达到7层时,临界荷载趋于稳定。     

弹性板水下爆炸冲击载荷的修正虚拟流体方法分析

研究非接触水下爆炸中板结构厚度和密度对冲击载荷和空化演变的影响.将近期发展的修正的虚拟流体方法推广应用于处理可压缩流体与弹性板结构的非线性相互作用.研究发现,假设结构不发生断裂破坏,较小的板厚度或密度可以减弱爆炸波对结构的冲击,冲击载荷随着厚度或密度的增大非线性地趋向于固壁边界下的结果.而且较小的板厚度或密度可以促使空化较早形成,产生较大的空化区,并推迟和减弱空化破裂对结构的二次冲击.     

截面几何参数对帽型梁轴向冲击响应的影响

帽型梁结构作为汽车前纵梁主要部件,其轴向冲击变形模式和吸能特性是汽车被动安全设计的主要参考指标。为此,对带有倒角的帽型梁进行了初始能量为17.8kJ的落锤轴向冲击实验和数值模拟。保持梁结构的质量不变,对不带倒角和直角弯折的两种截面梁进行同等条件的数值模拟,在一定范围内探讨截面几何参数对帽型梁的变形模式、变形量、吸能总量、峰值载荷、平均碰撞载荷和碰撞力效率的影响。结果表明:对于带有倒角的帽型梁,其变形模式和变形量的计算结果与实验结果基本吻合,验证了计算模型的合理性;倒角的存在使结构变形模式从非紧凑型向紧凑型转变,提高了缓冲效果,降低了峰值载荷;弯折角度由93°变为90°时,对变形模式的影响较小,非直角弯折梁的吸能效果较直角弯折梁好。因此,截面几何参数对帽型梁结构的变形模式和吸能特性有一定影响。     

简支圆板在平头弹丸撞击下的变形与穿透

 采用准静态近似理论方法分析简支圆板在平头弹丸正撞下的变形和穿透。首先基于虚功原理得到了静态荷载位移关系,并将其用于预测低速冲击下圆板的能量吸收能力。当考虑了材料的应变率敏感性,并且不发生绝热剪切冲塞破坏的前提下,理论预测和实验结果吻合良好。     

爆轰加载下锡金属连续层裂损伤机理的数值分析

结合实验对所采用的计算程序和损伤模型进行验证,在此基础上开展了爆轰加载下锡材料连续层裂损伤机理研究。结果显示:锡靶板的破坏模式与加载强度、加载波形以及靶板的几何结构相关;材料初始微结构的作用反映在对临界截止孔隙度的影响上,进而影响靶板的损伤破坏;损伤模型中临界截止孔隙度越大,靶板的破坏程度越小。此外,材料拉伸、压缩损伤的计算结果与相应实验结果的对比显示,材料的损伤主要以拉伸损伤破坏为主。     

金属蜂窝夹芯结构抗水下冲击性能

为揭示高强度水下爆炸冲击载荷作用下金属夹芯结构的抗冲击性能,在实验室开展小尺寸水下爆炸加载技术对金属蜂窝夹芯结构性能影响的实验研究。基于实验结果,开展了全尺寸数值模拟金属蜂窝夹芯结构在水下冲击载荷作用下的动态响应和抗冲击性能研究。结果表明,数值模拟、实验和理论模型计算的结果具有良好的一致性。由于蜂窝芯材相对密度对夹芯结构能量耗散方式和载荷传递机制的影响,结构动态响应、失效模式以及抗冲击性能随着冲击强度的变化表现出较为明显的不同。通过抗冲击参数分析,建立了反映金属蜂窝夹芯结构抗冲击性能的结构横向变形、固支反力、透射脉冲和塑性能耗随冲击强度和芯材相对密度变化的结构-载荷-性能量化关系。     

Axisymmetric buckling of the circular graphene sheets with the nonlocal continuum plate model

In this article, the buckling behavior of nanoscale circular plates under uniform radial compression is studied. Small-scale effect is taken into consideration. Using nonlocal elasticity theory the governing equations are derived for the circular single-layered graphene sheets (SLGS). Explicit expressions for the buckling loads are obtained for clamped and simply supported boundary conditions. It is shown that nonlocal effects play an important role in the buckling of circular nanoplates. The effects of the small scale on the buckling loads considering various parameters such as the radius of the plate and mode numbers are investigated.     

Free vibration of three-dimensional multilayered magneto-electro-elastic plates under combined clamped/free boundary conditions

In this paper, we study the free vibration of multilayered magneto-electro-elastic plates under combined clamped/free lateral boundary conditions using a semi-analytical discrete-layer approach. More specifically, we use piecewise continuous approximations for the field variables in the thickness direction and continuous polynomial approximations for those within the plane of the plate. Group theory is further used to isolate the nature of the vibrational modes to reduce the computational cost. As numerical examples, two cases of the lateral boundary conditions combined with the clamped and free edges are considered. The non-dimensional frequencies and mode shapes of elastic displacements, electric and magnetic potentials are presented. Our numerical results clearly illustrate the effect of the stacking sequences and magneto-electric coupling on the frequencies and mode shapes of the anisotropic magneto-electro-elastic plate, and should be useful in future vibration study and design of multilayered magneto-electro-elastic plates.     

Large amplitude vibrations and damage detection of rectangular plates

In this work, geometrically nonlinear vibrations of fully clamped rectangular plates are used to study the sensitivity of some nonlinear vibration response parameters to the presence of damage. The geometrically nonlinear version of the Mindlin plate theory is used to model the plate behaviour. Damage is represented as a stiffness reduction in a small area of the plate. The plate is subjected to harmonic loading with a frequency of excitation close to the first natural frequency leading to large amplitude vibrations. The plate vibration response is obtained by a pseudo-load mode superposition method. The main results are focussed on establishing the influence of damage on the vibration response of the plate and the change in the time-history diagrams and the Poincaré maps caused by the damage. Finally, a criterion and a damage index for detecting the presence and the location of the damage is proposed. The criterion is based on analysing the points in the Poincaré sections of the damaged and healthy plate. Numerical results for large amplitude vibrations of damaged and healthy rectangular and square plates are presented and the proposed damage index for the considered cases is calculated. The criterion demonstrates quite good abilities to detect and localize damage.     

弓形流道快速充电模块液冷板流动散热特性研究

采用数值方法对电动汽车快充模式下的液冷板散热特性进行模拟,设计四种水力半径相同、截面形状不同的弓形冷板槽道,研究不同流动特征下液冷板槽道截面特性对电动汽车快充模块散热的影响,结果表明:在相同水力半径条件下,弓形通道液冷板截面特征对冷板散热特性影响很大,且散热强弱顺序随Re增大发生转变,Re<265时,矩形(4×12mm)截面散热最好;Re>265时,方形通道截面散热最好。此外,各工况下圆形通道散热效果均表现为最差。     

二维空心散射体声子晶体板的低频带隙特性及其形成机理

利用有限元方法,对设计的涂有硅橡胶包裹层的空心铅柱体嵌入到4个环氧树脂短连接板中构成的声子晶体板的低频带隙特性进行了研究,分析了其能带结构、传输损失及位移场。与正方连接板粘连结构、嵌入结构和细连接短板粘连结构这3种传统声子晶体板的带隙特性作对比,说明具有包裹层、短连接板结构的声子晶体板更容易产生低频宽带;观察位移矢量场的振动模态,并结合弹簧质量模型,解释了带隙形成的机理;通过讨论连接板的宽度、散射体的内外半径及高度对第一完全带隙的影响,说明连接板宽度越窄,厚度越小,散射体内半径越小,外半径越大,高度越高,越有利于带隙的扩展。      

Vibration of moderately thick square orthotropic stepped thickness plates

Numerous studies that address the vibration of stepped thickness plates are reported in the literature. Predominately, classical plate theory has been used to formulate studies for both isotropic and anisotropic stepped plates. Mindlin plate theory has been employed to obtain results for thick isotropic stepped thickness plates. Exact solutions, Rayleigh-Ritz, differential quadrature and finite element methods have been employed to compute results for frequency of vibration. Results for frequency of vibration for thick orthotropic stepped thickness plates are presented here using orthorhombic material properties of aragonite. The finite element method has been used to compute frequencies and determine mode shapes for simply supported and clamped square Mindlin plates.     

爆炸载荷作用下钢-混凝土-钢组合板的动态响应数值模拟

钢-混凝土组合结构的抗爆性能已成为防护工程和反恐防爆等领域的研究热点。以钢-混凝土-钢组合板为例,利用有限元软件ABAQUS对爆炸载荷作用(爆距为2.5~7.5 m,TNT炸药量为50~100 kg)下该结构的破坏形态和动力学性能进行了数值模拟。研究结果表明,组合板的破坏形态与炸药量和爆距有关。炸药量越大,爆距越小,组合板的破坏程度越明显。当TNT炸药量为100 kg、爆距为2.5 m时,组合板发生明显的翘曲,出现了塑性铰。钢板的存在有效地抑制了核心混凝土的剥落。在爆距相同的条件下,炸药量越大,组合板的变形越明显,跨中挠度和峰值速度也越大。当炸药量相同(100 kg)时,与爆距为7.5 m相比,爆距为5.0 m时组合板的跨中挠度为其1.53倍,爆距为2.5 m时组合板的跨中挠度为其5.01倍。     

Vibrations of nearly annular and circular plates

A general procedure is presented to determine the natural frequencies and mode shapes of nearly annular and circular plates. A straightforward perturbation procedure is used with a transfer of the boundary conditions to obtain solutions given by simple expressions. As well as yielding good accuracy quantitatively, the method accurately predicts qualitative behavior. Numerical results are presented for clamped elliptical and square plates.     

Exact closed-form frequency equations for thick circular plates using a third-order shear deformation theory

This paper presents, for the first time, exact closed-form frequency equations and transverse displacement for thick circular plates with free, soft simply supported, hard simply supported and clamped boundary conditions based on Reddy's third-order shear deformation theory. Hamiltonian and minimum potential energy principles are used to extract the equations of dynamic equilibrium and natural boundary conditions of the plate. The new formulation is verified by comparing the results with their counterparts reported in open literature. Natural frequencies of circular plates with different boundary conditions are tabulated in dimensionless form for various values of thickness-radius ratios. The results presented on the basis of exact, closed-form frequency equations are expected to serve as reliable benchmarks.