接触爆炸对底部有土垫层纤维混凝土板破坏效应试验研究

采用钢纤维混凝土、聚丙烯纤维混凝土、钢筋混凝土3种材料共24块板试件进行了接触爆炸试验。对试验现象进行了描述,由迎爆坑尺寸拟合分析得到了3种材料的爆炸介质压缩系数。采用ЛяхоB公式对试验测得的土压峰值进行了拟合分析,结果表明,随试件厚度的增加,砂土中应力波峰值衰减更显著,相同比例爆距的土压值明显减小,并由试验结果得到了底部有土垫层介质情况下混凝土板临界爆炸贯穿厚度计算公式。     

土体爆炸压密的原理及试验研究

针对目前土体爆炸压密理论研究不够深入、施工中主要依靠工程经验确定爆炸参数的现状,建立了基于塑性力学和爆炸力学的土体爆炸压密模型,推得压密效果(压密范围、压密程度)与爆炸参数之间的关系式,并通过室外试验进行验证.在孔径为48 mm的炮孔中进行了不耦合系数分别为2.000、1.714、1.500、1.333、1.200、1...     

锥形端部弹体在岩石(混凝土)介质层中侵彻实用计算方法

采用刚塑性不可压缩的介质模型 ,用极限分析理论的上限方法 ,通过建立动力学许可速度场得到介质对弹体侵彻的静阻力分量 ,通过破碎介质动量守恒条件得到弹体侵彻的动阻力分量 ,在模型中还考虑了介质的尺度关系和弹体的弹头形状两种影响因素。侵彻过程中的速度、加速度、阻力和经历时间通过弹体的运动方程增量计算得到。通过与几种常用经验公式比较说明了本文方法的实用和可靠性。     

硅酸铝棉对火焰速度和爆炸超压的抑制作用

为研究硅酸铝棉位置、长度对预混气体爆炸超压和火焰速度的抑制规律,进行了硅酸铝棉抑制管道内预混气体爆炸实验,在管路内置入硅酸铝棉,以室温常压下化学计量浓度的C2H2/air预混气体为介质。结果表明,当硅酸铝棉长度超过速度临界长度时,能够有效抑制火焰速度。当硅酸铝棉长度超过压力临界长度时,能够有效抑制爆炸超压。速度临界长度的大小与硅酸铝棉入口火焰速度有关。压力临界长度的大小与硅酸铝棉入口爆炸超压有关。压力临界长度小于速度临界长度,说明硅酸铝棉对压力的抑制效果更加显著。     

梯度多胞牺牲层的抗爆炸分析

运用一维非线性塑性冲击波模型和细观有限元模型对密度梯度多胞牺牲层的抗爆炸性能进行了分析。基于率无关的刚性-塑性硬化模型,建立了描述冲击波在多胞牺牲层中传播的控制方程,分别给出了正、负密度梯度多胞材料在指数型爆炸载荷作用下的响应特性。研究了可正好吸收爆炸能量的梯度多胞牺牲层的临界厚度与载荷强度、覆盖层质量、多胞材料的密度梯度等参数之间的关系,给出了以临界厚度和支撑端应力峰值为指标的密度梯度设计图。运用二维细观有限元模型验证了基于非线性塑性冲击波模型的抗爆炸分析的有效性。     

石灰岩中不同埋深爆炸自由场直接地冲击参数的预计方法

通过现场实验,研究了石灰岩中常规装药不同埋深爆炸自由场直接地冲击参数的传播规律.采用了等效当量埋深系数的工程处理方法来描述不同爆炸埋深地冲击效应,并给出了石灰岩中不同埋深爆炸应力等效当量埋深系数和质点加速度等效当量埋深系数的计算公式,从而得到了石灰岩介质中不同埋深爆炸地冲击参数随比例距离的预计公式.     

不锈钢-普碳钢的双面爆炸复合

为了解决现行爆炸复合装药方式落后及炸药爆炸的能量利用率极低的问题，使用了一种保证装药质量的蜂窝结构炸药，并将该蜂窝结构炸药应用于一次起爆可复合二块复合板的双面爆炸复合技术。进行了7 mm厚的蜂窝结构炸药用于3 mm厚的不锈钢板和16 mm厚的Q235钢板的双面爆炸复合实验；并计算得到了复板碰撞速度的上下限及2组实验中复板的碰撞速度。由于受到蜂窝材料和双面复板的多向约束，炸药的临界厚度显著降低，乳化炸药在5 mm厚度时仍可以稳定爆轰。研究结果表明:和现行的单面爆炸复合相比，在复合相同数量复合板的情况下，采用蜂窝结构炸药的双面爆炸复合技术中，炸药的使用量节省了77%，炸药的能量利用率得到显著提高；计算与实验结果一致性较好。     

爆炸冲击振动下人体抛离问题的分析

采用单自由度模型研究了爆炸冲击振动下人体抛离问题。提出了人体抛离的飞离条件,推导了人体飞离时刻和飞离速度计算公式,为定量研究爆炸冲击振动下人员冲击伤和碰撞伤及人员隔冲问题提供了参考。     

考虑约束爆炸后产物发生化学反应的约束空间内准静态温度计算

考虑爆炸产物发生化学反应产生的影响,对约束爆炸后约束空间内准静态温度的计算进行了研究。以能量守恒定律为基础,考虑爆炸产物的化学反应动力学过程,推导得到约束空间准静态温度的计算公式和方法,使用C++语言编写了计算程序,并对TNT炸药约束爆炸的情况进行了计算。计算结果表明,对于约束爆炸,爆炸产物发生的化学反应对约束空间内温度的变化有明显影响,且不同的药量体积比条件下,准静态温度的变化趋势不同。研究结果可为更准确的计算约束爆炸后的准静态温度及其他爆炸参数提供有效的方法。     

碳氢燃料空气混合物无约束起爆临界起爆能估算

本文在矩形激波管内和无约束条件下分别测定了不同当量比的丁烷和空气混合物的临界起爆能，并利用Ｒａｍａｍｕｒｔｈ提出的爆炸长度的概念，推导出可以很方便的由平面起爆估算无约束起爆临界起爆能的公式。根据此式估算的起爆能结果与实验结果吻合较好。     

弹性压应力波下直杆动力失稳的机理的判据

基于应力波理论和失稳瞬间能量的转换和守恒,导出了一个直杆动力分岔失稳的准则：（1）直杆在发生分岔失稳的瞬间所释放出的压缩变形能等于屈曲所需变形能与屈曲动能之和;（2）在上述能量转换过程中,能量对时间的变化率服从守恒定律。应用临界条件（1）推导出的直杆动力失稳的控制方程和杆端边界条件以及连续条件,与应用哈密顿原理推导的结果完全相同,但不足以构成求解直杆动力失稳问题的完备定解条件,导出包含两个特征参数的一对特征方程。从而建立了求解直杆动力失稳模态和两个特征参数（临界力参数和失稳惯性项指数参数即动力特征参数）的较严密理论方法。     

Torsional vibration and stability of functionally graded orthotropic cylindrical shells on elastic foundations

In this study, the torsional vibration and stability problems of functionally graded (FG) orthotropic cylindrical shells in the elastic medium, using the Galerkin method was investigated. Pasternak model is used to describe the reaction of the elastic medium on the cylindrical shell. Mixed boundary conditions are considered. The material properties and density of the orthotropic cylindrical shell are assumed to vary exponentially in the thickness direction. The basic equations of the FG orthotropic cylindrical shell under the torsional load resting on the Pasternak-type elastic foundation are derived. The expressions for the critical torsional load and dimensionless torsional frequency parameter of the FG orthotropic cylindrical shell resting on elastic foundations are obtained. The effects of variations of shell parameters, the exponential factor characterizing the degree of material gradient, orthotropy, foundation stiffness and shear subgrade modulus of the foundation on the critical torsional load and dimensionless torsional frequency parameter are examined.     

一种岩石断裂韧度试样应力强度因子的三维边界元法标定

用三维边界元法(BEM)标定了一种岩石断裂韧度试样的柔度,求出了这种试样的平均无量纲应力强度因子(SIF),并得到了对应于最大载荷时的临界裂纹长度和平均无量纲SIF的最小值.     

Approximate nonreflecting inflow-outflow boundary conditions for the calculation of navier-stokes equations in internal flows

In this paper, the nonreflecting boundary conditions based upon fundamental ideas of the linear analysis are developed for gas dynamic equations, and the modified boundary conditions for Navier-Stokes equations are proposed as a substitute of the nonreflecting boundary conditions inside boundary layers near rigid walls. These derived boundary conditions are then applied to calculations both for the Euler equations and the Navier-Stokes equations to determine if they can produce acceptable results for the subsonic flows in channels. The numerical results obtained by an implicit second-order upwind difference scheme show the effectiveness and generality of the boundary conditions. Furthermore, the formulae and the analysis performed here may be extended to three dimensional problems. recommended by Prof. Cui Erjie     

Free convection on a vertical plate with uniform and constant heat flux in a thermally stratified micropolar fluid

This paper analyzes flow and heat transfer characteristics of the free convection on a vertical plate with uniform and constant heat flux in a thermally stratified micropolar fluid. The dimensionless forms of boundary layer equations and their associated boundary conditions have been derived and the numerical results have been obtained using the method of cubic spline collocation with a finite difference scheme. The effects of the micropolar and stratification parameters on the dimensionless wall temperature, skin friction parameter and wall couple stress are discussed.     

弹性地基上多孔功能梯度材料矩形板的自由振动与临界屈曲载荷分析

多孔功能梯度材料(FGM)构件的特性与孔隙率和孔隙分布形式有密切关系。本文基于经典板理论,考虑不同孔隙分布形式时修正的混合率模型,研究Winkler弹性地基上四边受压多孔FGM矩形板的自由振动与临界屈曲载荷特性。首先利用Hamilton原理和物理中面的定义推导Winkler弹性地基上四边受压多孔FGM矩形板自由振动的控制微分方程并进行无量纲化,然后应用微分变换法(DTM)对无量纲控制微分方程和边界条件进行变换,得到计算无量纲固有频率和临界屈曲载荷的代数特征方程。将问题退化为孔隙率为零时的FGM矩形板并与已有文献进行对比以验证其有效性。最后计算并分析了梯度指数、孔隙率、地基刚度系数、长宽比、四边受压载荷及边界条件对多孔FGM矩形板无量纲固有频率的影响以及各参数对无量纲临界屈曲载荷的影响。     

Characteristic-value analysis for plastic dynamic buckling of columns under elastoplastic compression waves

The characteristic-value analysis of plastic dynamic buckling is presented for columns under the action of elastoplastic compression wave caused by an axial-step load. Two critical conditions constituting a dynamic instability criterion are derived on the basis of transformation and conservation of energy. The governing equations, the boundary conditions and the continuity conditions derived by the use of the first critical condition are the same as those given by the adjacent-equilibrium criterion and are insufficient for determining two characteristic parameters involved in the governing equations. A supplementary restraint equation for buckling deformations at the plastic-wave front and the elastic-wave front is derived by the use of the second critical condition. Then, a couple of characteristic equations for two characteristic parameters are derived on the condition that the governing equations have non-trivial solutions satisfying the boundary conditions, the continuity conditions and the supplementary restraint equation. The critical-load parameters, dynamic characteristic parameter (exponent parameter of inertia term) and dynamic buckling modes are calculated from the solutions of the characteristic equations.     

Scaling group transformation for MHD boundary layer flow over permeable stretching sheet in presence of slip flow with Newtonian heating effects

Taking into account the slip flow effects, Newtonian heating, and thermal radiation, two-dimensional magnetohydrodynamic （MHD） flows and heat transfer past a permeable stretching sheet are investigated numerically. We use one parameter group transformation to develop similarity transformation. By using the similarity transformation, we transform the governing boundary layer equations along with the boundary conditions into ordinary differential equations with relevant boundary conditions. The obtained ordinary differential equations are solved with the fourth-fifth order Runge-Kutta- Fehlberg method using MAPLE 13. The present paper is compared with a published one. Good agreement is obtained. Numerical results for dimensionless velocity, temperature distributions, skin friction factor, and heat transfer rates are discussed for various values of controlling parameters.     

轴向压应力波下圆柱壳弹性动力失稳的判据与机理

基于动力失稳瞬间能量的转换和守恒,推导提出了受轴向力圆柱壳弹性动力失稳的判据和两个临界条件,由第一个临界条件导出的圆柱壳弹性动力失稳的控制方程、边界条件、屈曲变形连续与利用Hamilton原理的结果完全相同,但不足以确定包含在本问题中的两个特定特征参数（临界载荷参数和动力特征参数）,由第二个临界条件导出压缩波前的屈曲变形约束方程,基于控制方程有满足边界条件、变形连续条件和波前约束方程的非平凡解的条件,导出关于两个特征参数的一对特征方程,基于特征方程的解,精确地计算出临界载荷参数和动力特征参数的值以及动力失稳态态,由此建立了轴向力作用下圆桩壳弹性动力失稳的特征值分析方法。     

TORSIONAL VIBRATIONS OF A RIGID CIRCULAR PLATE ON SATURATED STRATUM OVERLAYING BEDROCK

The torsional vibration of a rigid plate resting on saturated stratum overlaying bedrock has been analysed for the first time. The dynamic governing differential equations for saturated poroelastic medium are solved by employing the technology of Hankel transform. By taking into account the boundary conditions, the dual integral equations of torsional vibration of a rigid circular plate are established, which are further converted into a Fredholm integral equation of the second kind. Subsequently, the dynamic compliance coefficients of the foundation on saturated stratum, the contact shear stress under the foundation and the angular amplitude of the foundation are evaluated. Numerical results indicate that, when the dimensionless height is bigger than 5, saturated stratum overlaying bedrock can be treated as saturated half space approximately. When the dimensionless frequency is low, the permeability of the soil must be taken into account. Furthermore, when the vibration frequency is a constant, the height of the saturated stratum has a slight effect on the dimensionless contact shear stress under the foundation.