冲击波对核反应堆安全壳的动力响应研究

本文用时域边界积分方程提出研究半球形核反应堆安全壳在爆炸冲击波作用下动力响应分析的计算模型。从空中爆炸和地面爆炸两方面探求壳体位移和变形过程,分析冲击波在壳体内的传播规律。计算了在水平冲击波作用下壳体的内力分布,其计算结果可以作为我国核电站设计的参考分析依据。     

Perturbation Method in the Problem of Compression-Shear Shock Load for a Nonlinear Elastic Half-Space

On the example of a one-dimensional nonstationary problem of oblique impact on the boundary of a nonlinear elastic isotropic half-space, the question of the manifestation of nonlinear deformation effects via basic evolution equations is studied. Much attention is given to the behavior of the solution behind the leading edge of a quasi-transverse shock wave. For particular cases of boundary conditions, it is shown that the onset region of the evolution equation of a quasi-transverse wave is preceded by a series of preliminary transitions to the intermediate internal problems of the small parameter method determined by the type of preliminary bulk deformation. This deformation consistently affects the distortion of the characteristic coordinates and the leading edge of the quasitransverse process. As a consequence, the transition to the evolution equation of quasi-transverse waves occurs with simultaneous change of all independent variables of the boundary value problem.     

Damage accumulation stages in polycrystalline duralumin under static fatigue loading

Two groups of mode changes in the internal structure of a cyclically loaded tension specimen containing a circular hole are analyzed. Their association with order-dependent parameters are also identified. Solutions are obtained and they show that stage I and II deformation in the vicinity of a macroscale stress concentrator is caused by an occupation wave where the velocity is bounded below certain limiting value. Stage III deformation occurs in the strain-localization region.     

Explosive loading of deformable gas-permeable axisymmetric structural elements

A mathematical model is proposed which describes the interrelated processes of unsteady elastoplastic deformation of stacks of woven metal wire mesh and wave processes in pore gas in a two-dimensional axisymmetric approximation. The nonlinear equations of the dynamics of two interpenetrating continua are solved numerically using a modified Godunov’s scheme. The problem of explosive loading of a multilayer shell with an internal permeable deformable layer is solved. The results of numerical solutions are compared with experimental data. The influence of the gas-permeable layer on shell deformation is determined.     

A physical model of the structure and attenuation of shock waves in metals

In this paper, a physical model of the structure and attenuation of shock waves in metals is presented. In order to establish the constitutive equations of materials under high velocity deformation and to study the structure of transition zone of shock wave, two independent approaches are involved. Firstly, the specific internal energy is decomposed into the elastic compression energy and elastic deformation energy, and the later is represented by an expansion to third-order terms in elastic strain and entropy, including the coupling effect of heat and mechanical energy. Secondly, a plastic relaxation function describing the behaviour of plastic flow under high temperature and high pressure is suggested from the viewpoint of dislocation dynamics. In addition, a group of ordinary differential equations has been built to determine the thermo-mechanical state variables in the transition zone of a steady shock wave and the thickness of the high pressure shock wave, and an analytical solution of the equations can be found provided that the entropy change across the shock is assumed to be negligible and Hugoniot compression modulus is used instead of the isentropic compression modulus. A quite approximate method for solving the attenuation of shock wave front has been proposed for the flat-plate symmetric impact problem.     

内部爆炸薄圆板的变形及有效载荷

为了研究内爆炸薄圆板的失效与作用载荷特性,在双圆筒装置内开展了铝质、钢质薄圆板内爆炸实验,分析了圆板破坏模式及比冲量载荷特性,并基于相同变形下载荷相等原理,得到了钢质圆板极限变形下的有效比冲量及作用时间,提出了该工况下圆板变形的预估模型。结果表明:在内爆炸载荷作用下,薄圆板的夹持边界和几何中心是应力集中区,产生了塑性大变形、拉伸撕裂、剪切断裂3种破坏模式;圆板的比冲量载荷由初始的波浪式增长逐渐转化为线性增长,30～80 g某温压装药使1 mm厚钢质圆板产生极限变形的有效比冲量作用时间在2.26～2.93 ms之间,经验证,圆钢板变形预估模型得到的装药质量与实验装药质量偏差小于13.3%。     

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.     

白云岩受压声学特性及其在裂缝研究中的应用

通过实验手段研究了白云岩在三轴和单轴加载过程中的声波波速、幅度、频谱特性的变化特征. 结果发现:(1)白云岩在受压变形过程中,声波波速的变化较好地反映了岩石内部裂缝的闭合、产生、扩展和贯穿等变化. 总体而言,横波波速比纵波能更好地预测裂缝的产生,而纵波对裂缝的非稳定发展或贯穿有较敏感的反映. (2)随着轴压的增大,纵、横波波形的末端都有散射波的出现,且横波波形末端的"鱼尾"状散射波信号更为明显(此时应力点为极限强度的60%左右),预示着岩石内部裂缝的产生和稳定扩展. (3)频谱曲线也很好地反映了岩石内部结构变形情况. 随着岩石受力的增大,频谱曲线上的振幅都呈现增大趋势,标志着岩石的压实阶段;当频谱曲线上低频段较高频段活跃时,标志着裂缝的产生;更有甚者,低频还会取代高频成为主频. (4)在岩石受压裂缝闭合阶段,首波振幅和频谱主振幅都呈现上升趋势;而在裂缝不稳定扩展阶段,主振幅表现出比首波振幅低的上升趋势;振幅曲线达到峰值后都存在一突降拐点,预示着岩石的贯通破坏. 研究对于地层岩石的动态长期监测和工程岩体的稳定性评价都具有重要的理论参考价值.      

金属柱壳膨胀断裂的实验与数值模拟

基于一端起爆的柱壳外爆加载装置,采用多普勒速度测量仪(DPS)及高速分幅相机联合诊断柱壳的膨胀断裂过程。实验获得了壳体表面的速度历史和膨胀变形、裂纹萌生扩展到爆轰产物泄露的动态图像。利用光滑粒子流体动力学方法(SPH)开展了对应的数值模拟,计算结果与实验结果吻合较好。实验与数值模拟结果系统地给出了冲击波入射柱壳角、爆轰波稀疏角、内壁速度压力历史及壳体变形应变、壳体断裂等物理信息。     

液层厚度对浮力-热毛细对流面型的影响

将Michelson光学干涉测量系统与图像处理技术相结合，发展形成一种实时诊断热毛细对流和浮力对流流体表面形貌的实验测量系统. 采用光学干涉测量方法研究了两端带有温差的矩形池内薄层流体的对流、表面变形、以及表面波的基本问题. 应用Fourier变换方法对实验结果进行计算和分析，得到了流体表面变形和表面波的定量的实验结果. 实验结果表明了在浮力-热毛细对流的发展过程中，首先出现流体的表面变形，之后在该变形的基础上，叠加了一个表面波的信息，该表面变形和表面波与流体的温度梯度、表面张力、以及浮力有直接的关系；表面波隐藏在表面变形内.     

Nonlinear analysis of governing laws of realization of the wave motion on the surface of a charged jet moving with respect to a material medium

On the base of analytic asymptotic calculations which are quadratic with respect to the ratio of the wave amplitude and the jet radius it is shown that the presence of a tangential jump in the velocity field on the jet surface leads to generation of a periodic wave motion on the interface between the media and has the destabilizing effect for both axisymmetric and bending and bending-deformation waves. It is found that there is a degenerate internal nonlinear resonance interaction between waves on the jet surface. This interaction may be of six different types in which the energy can be transferred between the interacting waves including waves of different symmetry. In the last case the energy is transferred from waves determining the initial deformation to axisymmetric waves.     

Influences of large deformation and rotary inertia on wave propagation in piezoelectric cylindrically laminated shells in thermal environment

Influences of large deformation (geometrical non-linear) and rotary inertia on wave propagation in a long, piezoelectric cylindrically laminated shell in thermal environment is presented in this paper. Nonlinear dynamic governing equations of piezoelectric cylindrically laminated shells are derived by means of Hamilton’s principle. The wave propagation modes are obtained by solving an eigenvalue problem. Numerical examples show that the characteristics of wave propagation in piezoelectric cylindrically laminated shells are relates to the large deformation, rotary inertia and thermal environment of the piezoelectric cylindrically laminated shells. The effect of large deformation, rotary inertia and thermal load on wave propagation in the piezoelectric cylindrically laminated shells is discussed by comparing with the result from the small deformation (geometrical linear shell theory). This method may be used to investigate wave propagation in various laminated material, layers numbers and thickness of piezoelectric cylindrically laminated shells under large deformation. The results carried out can be used in the ultrasonic inspection techniques and structural health monitoring.     

Dynamic neck development in a polymer tube under internal pressure loading

The initiation and growth of necks in polymer tubes subjected to rapidly increasing internal pressure is analyzed numerically. Plane strain conditions are assumed to prevail in the axial direction. The polymer is characterized by a finite strain elastic–viscoplastic constitutive relation and the calculations are carried out using a dynamic finite element program. Numerical results for neck development are illustrated and discussed for tubes of various thicknesses. The sensitivity to the wave number of the thickness imperfections is studied with a focus on comparing a long wave length imperfection and a short wave length imperfection. After some thinning down at the necks, the mode of deformation switches to neck propagation along the circumference of the tube. A case is shown in which the necks have propagated along the entire tube wall, so that network locking in the polymer results in high stiffness against further expansion of the tube. The rate dependence of the necking behavior gives noticeable differences in neck development for slow loading versus fast loading.     

构型弹体跌落冲击载荷及结构响应特性

为深入认识跌落冲击条件下构型弹体内部的载荷传递规律及结构响应特征,促进战斗部装药安定性评估和结构设计,结合数值模拟和应力波分析手段,研究了构型弹体在跌落过程中的冲击响应特征,主要关注内部药柱的变形和损伤特性,并讨论跌落姿态、装药构型和跌落高度等因素的影响。结果表明,在跌落冲击条件下,构型弹体装药的变形并非由药柱同壳体的直接撞击作用主控,而主要受到弹体内部应力波传播的影响。装药结构最大变形和损伤区域并不位于药柱外侧同壳体相接触的位置,而位于内部区域。冲击应力波在壳体和药柱之间的透射特征、在壳体和装药内部的反射和叠加特性等决定了药柱的主要变形区域及其变形程度。跌落姿态对药柱的响应特征和变形形貌具有重要影响,导致装药安定性风险从高到低排序的跌落姿态依次为尾部向下垂直跌落、水平跌落、头部向下垂直跌落和倾斜跌落。药柱构型也具有重要作用,其中药柱分段界面容易使得药柱变形程度增大,但对装药过载以及变形分布特征的影响相对较小;隔板结构则容易增大装药过载,同时导致药柱的局域变形位置和变形程度均发生改变。跌落高度对药柱变形区域分布特征的影响较小,对载荷幅值、变形程度和分布范围大小等则具有重要作用,随跌落高...     

舱内爆炸载荷下箱型舱室角隅连接结构设计

通过有限元软件LS-DYNA建立了舱内爆炸载荷下箱型舱室动响应数值模型,并借助文献试验结果验证了数值模型的可靠性,研究了平板型、内凹型、外凸型、箭头型、箭矢型、背面弧型等6种角隅连接结构对舱内爆炸载荷下箱型舱室变形、特征位置压力和破坏模式的影响,分析了内爆效应下角隅连接结构的失效机理。数值结果表明:舱壁角隅位置是舱内爆炸载荷作用下舱室易发生破坏撕裂的特征位置;相比无连接结构,平板型连接结构对舱壁最大塑性变形改善最大,降低幅度达到了31.9%;背面弧型连接结构能够使箱型舱室角隅等效塑性应变降低约60%;设置连接结构能够改变高塑性应变的发生位置,进而改变箱型舱室的破坏模式;采用平板型、内凹型、背面弧型连接结构的箱型舱室能够有效避免角隅失效破坏。     

爆炸下球壳变形空间周期分布的理论计算方法

早期研究提出了对振动叠加应变增长现象的解剖式分析方法,进而发现爆炸加载下带扰动源球壳上的弯曲波和壳体变形呈空间周期分布的规律。参考Timoshenko梁的弯曲理论,基于平截面假定和壳体发生较小的弯曲变形的假设,推导出球壳上弯曲波波速和波长的关系,计算得到最短弯曲波和与膜振动频率相近的弯曲波的波速,还结合早期研究提出的壳体变形分布周期与弯曲波波速的关系,计算得到了壳体变形空间分布的周期。结果表明:（1）理论计算结果与数值仿真结果基本吻合,其中弯曲波波速的计算结果与数值仿真结果相差在15%以内,壳体变形空间分布周期的计算结果与数值仿真结果相差在12%以内;（2）弯曲波波长越短,波速越快,当波长无限短时,波速趋于极限值,约为声速的0.574倍。本计算方法为解剖式分析方法提供了一定的理论依据。     

位移浅水内孤立波

研究两层浅水系统中的内孤立波,该系统由两层常密度不可压缩无黏性水组成。利用Lagrange坐标和Hamilton原理,推导了两层浅水系统的位移浅水内波方程,并进一步导出了两层浅水系统的位移内孤立波解。数值实验表明,位移内孤立波与经典的KdV内孤立波吻合很好,说明Lagrange坐标和Hamilton方法适用于内波分析,可以为构造内波分析的保辛方法提供一种途径。     

高速铁路长隧道压缩波波前变形规律分析

高速列车进入隧道时产生的压缩波在长隧道中传播时会产生波前变形,即波前压力梯度发生变化。线路测量和学者的研究表明,隧道出口处微气压波的强度与压缩波波前压力梯度最大值成正比,而微气压波的大小又与隧道出口的爆破音直接相关,因此有必要研究压缩波在长隧道中传播时的波前变形规律。采用计算流体力学三维动态仿真计算方法,对长隧道内压缩波的生成和传播过程进行研究。证明了压缩波的波前变形不仅与初始压缩波生成时的惯性运动和气体摩擦相关,而且与列车在隧道中的运动相关,即列车运动产生的能量输入会影响压缩波波前的变形。通过多工况计算,获得了隧道内压力梯度的最大值及其出现位置与列车速度和隧道阻塞比之间的变化规律。     

简化Holmboe分层流体密度剖面的形成及其内波实验

本研究在内波水槽中形成了具备Ｈｏｌｍｂｏｅ模式基本特征的密度剖面，在此流场中成功地进行了第一模态单板造波内波实验，并进而对半板造波的方案给予了分析和检验。     

坚硬岩石在强冲击荷载作用近区的性状研究

根据坚硬岩石的性质,利用力学模型分析了在冲击荷载作用下的岩石破坏过程,经由弹性状态向内摩擦状态的转变,最终达到流体力学状态。通过对内摩擦状态的分析,认为在强冲击荷载区域的变形近似为一维变形状态。冲击荷载作用在岩石中产生的应力波可以看作类似于冲击波的短波,在波阵面附近的某个狭窄区域内将发生参数的急剧变化。根据近区变形状态与质量守恒导出了侵彻近区的速度场表达式。根据短波的研究,给出了近区应力波的衰减规律。