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1.
浇铸类炸药由于质地软、波阻抗及波速都很低,通过传统SHPB实验方法无法得到准确的应力应变数据。透射杆信号幅值过低、试样应力平衡均匀性不高以及大应变加载引起的入射波反射波重叠失效,是进行浇铸类炸药SHPB实验的难点所在。本文中对传统SHPB实验方法进行改进,在试样两端面加装石英晶体应力计,引入石英计所获得的应力数据与应变片测得数据共同对试样应力应变状态进行计算。该方法可以提高透射信号幅值,提供试样大应变加载,避免了入射波反射波重叠导致的信号失效问题,修正了SHPB实验过程中的应力时空不均匀性的影响,提高了实验结果的可靠性。利用改进后的实验方法对典型浇铸类炸药进行了实验研究,得到了较准确的应力应变曲线。 相似文献
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利用研制的岩石动静组合加载实验装置进行循环冲击实验,研究了在循环冲击过程中岩石典型的
动态应力应变曲线及反射波和透射波的变化规律。结果表明:岩石在循环冲击过程中的动态应力应变曲线可
分为压密阶段、弹性阶段、内部裂纹扩展的加载阶段、第1卸载阶段和第2卸载阶段等5个阶段。在相同入射
波循环作用下,随着循环次数的增加,岩石的反射波峰值越来越大,反射波峰值出现的时间越来越迟,透射波
峰值越来越小,透射波峰值出现的时间越来越早,表明在循环冲击过程中岩石内部损伤逐渐累积,从而导致抵
抗外部冲击载荷的能力逐渐降低。 相似文献
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运用Holmquist-Johnson-Cook (HJC) 本构模型对混凝土的SHPB实验进行了数值模拟。解决了罚函数算法中罚因子合理数值的选取问题。利用模拟结果按SHPB两波法重构了试样的应力应变曲线。分析了混凝土材料的SHPB实验得到应力应变曲线的有效段范围和各段的力学规律。通过比较实际混凝土材料SHPB实验和数值模拟得到的应力应变曲线,发现两者体现的力学行为很相似,即HJC模型是描述该类材料的一种合理本构模型。模拟了试样不同平行度公差下的SHPB实验,发现在一定应变率范围内其影响程度远大于试样应力(应变)不均匀性。 相似文献
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分层流体中内孤立波在台阶上的反射和透射 总被引:2,自引:0,他引:2
基于匹配渐近展开和格林函数的方法,研究了两层流体系统中内孤立波在台阶地形上透射、
反射及其分裂的演化特征. 通过保角变换和求解奇异Fredholm积分方程,获得了反映地形
效应对Boussinesq方程影响的约化边界条件,藉此建立了KdV演化方程的``初值'问题,
根据散射反演理论获得了反射波和透射波的解析表达式. 分析结果表明:上下流体层的厚度
比、密度比以及台阶高度对于反射和透射波振幅及其分裂具有显著的影响. 尤其当上层流体
厚度小于下层厚度时,由于存在临界点,在其附近反射波的幅值随台阶高度的演化由单调增
变为单调减,透射波的幅值由单调减变为单调增;上台阶的反射波与入射波反相,其最大幅
值可达到入射波的数倍;此外,下台阶反射波也可发展为单支孤立波,它区别于单层流体中
反射波仅为衰减的振荡波列. 相似文献
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采用改进的SHPB方法对泡沫铝动态力学性能的研究 总被引:5,自引:1,他引:5
本文改进了传统的分离式霍布金森压杆(SHPB)技术,采用夹在透射杆中的PVDF压电计直接测量透射杆中的应力时程.同时,采用输入波形整形技术,通过调整加载波形,使试样加载过程中保证均匀变形及应力平衡.利用此改进了的SHPB技术对泡沫铝进行了高应变率下的动态压缩实验.实验结果表明:泡沫铝的动态应力应变曲线具有泡沫材料的应力应变曲线的“三阶段”特征(elastic region,collapse region and densification region),并且应变率对其力学性能影响明显. 相似文献
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建立描述SHPB实验中线性粘弹性试件内部应力波传播的控制方程组,根据试件两端与入射杆及透射杆接触的应力波特征关系给出耦合边界条件.对方程组和定解条件进行Laplace变换,求得试件内部应力在变换域像函数的表达式.采用数值反变换技术进行反Laplace变换,获得试件两端的应力时程曲线.对现有的固定Tal-bot反变换算法进行改进:将入射波像函数分解为基本部分和延迟部分,利用固定Talbot算法对基本部分入射波作用下的波动问题求解,其他部分的解通过延迟定理得到,最终解为两部分的叠加.采用这种改进算法得到的不同入射波下粘弹性试件的内部应力解与传统的基于特征线数值模拟方法的结果吻合.在此基础上探讨了粘弹性试件的几何参数和材料本构参数对透射波波形的影响. 相似文献
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Reflection and Transmission of Elastic Waves from the Interface of a Fluid-saturated Porous Solid and a Double Porosity Solid 总被引:1,自引:0,他引:1
The reflection and transmission characteristics of an incident plane P1 wave from the interface of a fluid-saturated single porous solid and a fluid-saturated double porosity solid are investigated.
The fluid-saturated porous solid is modeled with the classic Biot’s theory and the double porosity medium is described by
an extended Biot’s theory. In a double-porosity model with dual-permeability there exist three compressional waves and a shear
wave. The effects of the incident angle and frequency on amplitude ratios of the reflected and transmitted waves to the incident
wave are discussed. Two boundary conditions are discussed in detail: (a) Open-pore boundary and (b) Sealed-pore boundary.
Numerical results reveal that the characteristics of the reflection and transmission coefficients to the incident angle and
the frequency are quite different for the two cases of boundary conditions. Properties of the bulk waves existing in the fluid-saturated
porous solid and the double porosity medium are also studied. 相似文献
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The reflection and transmission of elastic waves through a couple-stress elastic slab that is sandwiched between two couple-stress elastic half-spaces are studied in this paper. Because of the couple-stress effects, there are three types of elastic waves in the couple-stress elastic solid, two of which are dispersive. The interface conditions between two couple-stress solids involve the surface couple and rotation apart from the surface traction and displacement. The nontraditional interface conditions between the slab and two solid half-spaces are used to obtain the linear algebraic equation sets from which the amplitude ratios of reflection and transmission waves to the incident wave can be determined. Then, the energy fluxes carried by the various reflection and transmission waves are calculated numerically and the normal energy flux conservation is used to validate the numerical results. The special case, couple-stress elastic slab sandwiched by the classical elastic half-spaces, is also studied and compared with the situation that the classical elastic slab sandwiched by the classical elastic half-spaces. Incident longitudinal wave (P wave) and incident transverse wave (SV wave) are both considered. The influences of the couple-stress are mainly discussed based on the numerical results. It is found that the couple-stress mainly influences the transverse modes of elastic waves. 相似文献
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Transverse wave at a plane interface between isotropic elastic and unsaturated porous elastic solid half-spaces 总被引:2,自引:0,他引:2
Wei-yun Chen Tang-dai Xia Miao-miao Sun Chao-jiao Zhai 《Transport in Porous Media》2012,94(1):417-436
Based on the poroelasticity theory, this article investigates the reflection and transmission characteristics of an incident plane transverse wave at a plane interface between an isotropic elastic half-space and an unsaturated poroelastic solid half-space. For this purpose, the effect of the saturation degree and frequency on the properties of the four bulk waves in unsaturated porous medium, i.e., three longitudinal waves and one transverse wave, are discussed at first. Two general cases of mode conversion are considered: (i) The initial transverse wave is incident from an unsaturated poroelastic half-space to the interface, and (ii) the initial transverse wave is incident from an elastic solid half-space to the interface. The expressions for the partition of energy at the interface during transmission and reflection process of waves are presented in explicit forms. At last, numerical computations are performed for these two cases and the results obtained are depicted, respectively. The variation of the amplitude ratios and energy ratios with the saturation degree and incident angle is illustrated in detail. It is also verified that, at the interface, the sum of energy ratios is approximately equal to unity as expected. 相似文献
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The propagation, reflection, and transmission of SH waves in slightly compressible, finitely deformed elastic media are considered in this paper. The dispersion relation for SH-wave propagation in slightly compressible, finitely deformed layer overlying a slightly compressible, finitely deformed half-space is derived. The present paper also deals with the reflection and refraction (transmission) phenomena due to the SH wave incident at the plane interface between two distinct slightly compressible, finitely deformed elastic media. The closed form expressions for the amplitude ratios of reflection and refraction coefficients of the reflected and refracted SH waves are obtained from suitable boundary conditions. For the numerical discussions, we consider the Neo-Hookean form of a strain energy function. The phase speed curves, the variations of reflection, and transmission coefficients with the angle of incidence, and the plots of the slowness sections are presented by means of graphs. 相似文献
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对粘接结构进行超声导波无损检测与评估是一个有挑战性的前沿性课题.针对此问题,研究了SH0导波在界面为理想连接的三层板状粘接结构中传播时的相位变化情况.首先基于波传播的控制方程,建立了粘接结构中反射和透射SH0导波相对于入射SH0导波的相位差解析模型.然后利用数值模拟计算了铝/环氧树脂/铝粘接结构中反射和透射SH0导波的相位差曲线.最后分析了入射角度和频厚积的变化对反射和透射SH0导波相位差的影响.结果表明,对于具体的粘接结构,反射和透射SH0导波在其中传播时的相位差变化主要依赖于入射角度、频率等参数.在特定的频厚积下,当声波水平入射时,反射和入射SH0导波同相位.无论入射角度为多大,随着频厚积的增大,反射SH0导波的相位差曲线均会产生周期性谐振.对于透射SH0导波,当声波垂直入射时,其相位差曲线的改变无规律可循;但是随着入射角度逐渐增大,透射SH0导波的相位差曲线逐渐变规则.所得结果可为实验时研究板状粘接结构中SH0导波的传播特性以及提取SH0导波回波中的有用信息和定位提供一定的理论指导. 相似文献
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连续分层流体中垂直薄板的水动力特性 总被引:1,自引:0,他引:1
研究了在线性连续分层流体中水波与半潜式刚性垂直薄板相互作用的问题. 在
Boussinesq近似下,基于分离变量法,导出了具有自由面的平面前进波的色散关系,建立
了半潜式刚性垂直薄板的反射与透射能量、水平波浪力的计算方法. 对给定的频率,当它大
于浮力频率时,流场中只有一种模态的平面前进波,当它小于浮力频率时,流场
中有无数多个模态的平面前进波,并证明了对每一种模态的入射波,其它每个模态水波的反射与透射能量是
相等的. 对水面漂浮和座底半潜式薄板的反射与透射能量,以及作用在薄板上的水平波浪力
进行了数值计算分析,表明了流体的线性连续分层效应对这些水动力的影响是不可忽视
的. 特别地,在入射波频率小于浮力频率时,与第1模态入射波的能量转化量及其对薄板产
生的水平波浪力相比,其它模态入射波的能量转化量及其对薄板产生的水平波浪力都要大得
多. 相似文献
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The reflection and transmission of an incident plane wave at an interface between water and a fluid-saturated double porosity
solid are investigated. The properties of the three compressional waves and one shear wave in double porosity media are discussed
in detail. The effect of the viscosity, permeability, and porosity on the phase velocity and attenuation of four bulk waves
is presented. Comparison between the double porosity theory and the Biot theory reveals that there exists obvious difference
in the phase velocity, attenuation and the reflection and transmission coefficients. Two cases of boundary conditions, i.e.,
the sealed-pore and the open-pore boundaries, are introduced in the numerical calculation. At last, the effect of the fracture
permeability and porosity on the reflection and transmission coefficients considered. It is revealed that the amplitudes of
the reflected and transmitted waves strongly depend the boundary condition, fracture permeability, and porosity. 相似文献
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Reflection and transmission of an incident plane wave at five types of possible interfaces between two dipo-lar gradient elastic solids are studied in this paper. First, the explicit expressions of monopolar tractions and dipolar trac-tions are derived from the postulated function of strain energy density. Then, the displacements, the normal derivative of displacements, monopolar tractions, and dipolar tractions are used to create the nontraditional interface conditions. There are five types of possible interfaces based on all possible combinations of the displacements and the normal derivative of displacements. These interfacial conditions with consid-eration of microstructure effects are used to determine the amplitude ratio of the reflection and transmission waves with respect to the incident wave. Further, the energy ratios of the reflection and transmission waves with respect to the incident wave are calculated. Some numerical results of the reflection and transmission coefficients are given in terms of energy flux ratio for five types of possible interfaces. The influences of the five types of possible interfaces on the energy parti-tion between the refection waves and the transmission waves are discussed, and the concept of double channels of energy transfer is first proposed to explain the different influences of five types of interfaces. 相似文献
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A. Chattopadhyay S. Gupta V.K. Sharma Pato Kumari 《International Journal of Solids and Structures》2009,46(17):3241-3256
The reflection and refraction pattern of elastic waves at a corrugated interface between two triclinic half-spaces is discussed. The incident wave is taken to be the cause of the interface disturbance and the reflected and refracted waves are effects. This leads to the causality requirement that the reflected and refracted waves must propagate away from the interface. Closed form expressions of reflection and transmission coefficients are derived using Rayleigh’s method of approximation. The formulae of reflection and transmission coefficients are derived in closed form for the first-order approximation of the corrugation. The analytical expressions of all the three phase velocities of qP, qSV and qSH waves have been derived. The variation of reflection and refraction coefficients with the angle of incidence and also with the corrugation parameter is shown. In this paper we have developed Graphical User Interface (GUI) Software in MATLAB which shows the variation of reflection and refraction coefficients with respect to incident angle and corrugation parameter. This software can be generalized to show the variation of reflection and refraction coefficients. Numerical computations are performed for a scientific model and the results obtained are shown graphically. 相似文献