波由单相弹性介质向横观各向同性液体饱和多孔介质传播时的反射与透射

研究了弹性波从单相各向同性弹性介质向双相各向异性液体饱和介质的传播问题.基于Biot的孔隙介质理论,并考虑动态渗透率,对以任意角度、任意频率入射的弹性波,解析地导出了在界面上的透射角、透射波波速和衰减系数,给出了各波在界面上的能量分配,数值计算了反射、透射系数与入射角、孔隙度等的关系曲线.     

损伤层对弹性波的反射与透射

本文研究了具有随机分布币形裂纹的损伤层对弹性波的反射与透射。分析了低频及裂纹密度不太高时损伤层的损伤状态对反射波与透射波的影响,为定量无损检测技术提供了一个简单的理论模型。     

两相介质中波在平面界面上的反射

借助Ｂｉｏｔ多孔介质中的波动方程,根据各种界面条件导出了波在两相介质各种界面上反射的一般计算公式。作为例子,数值计算了Ｐ１波入射于几种典型界面时,Ｐ１、Ｐ２和Ｓ波的反射系数与频率、入射角之间的关系。结果表明：各种波的反射系数与入射角、频率有关系,若把多孔介质当作单相均一固体处理,将会得到显著不同的结果。     

弹性波在准饱和土和弹性土界面的反射与透射

考虑土颗粒和孔隙流体的压缩性,根据准饱和土体的变形连续条件和平衡条件,推导了P1波(快压缩波)、P2波(慢压缩波)和S波的计算公式．根据Snell定理,研究了平面P1波从准饱和土体入射到弹性土层时在界面上的反射和透射,并绘制了反射系数、透射系数和界面应力、位移随入射角的变化曲线,结果表明:饱和度是影响界面效应的一个重要因素,当饱和度低于99％时,反射和透射系数以及应力和位移基本相等,变化不大,但当饱和度为100％时,虽然饱和度比99％提高了1％,但反射和透射系数以及应力和位移值比饱和度为99％时明显降低．     

声波在无限大多层板上的反射和透射的准确解

1、基于三维弹性理论的准确解本文中我们仅考虑这样的多层板,板内任何一点,都有一个与板面平行的材料特性对称面(z=常数)。(1).各向异性介质中波的传播利用文[1]中记号,弹性力学波动方程(无体力)为     

两相介质中波在平面界面上的反射

借助Ｂｉｏｔ多孔介质中的波动方程,根据各种界面条件导出了波在两相介质各种界面上反射的一般计算公式。作为例子,数值计算了Ｐ１波入射于几种典型界面时,Ｐ１、Ｐ２和Ｓ波的反射系数与频率、入射角之间的关系。结果表明:各种波的反射系数与入射角、频率有关系,若把多孔介质当作单相均一固体处理,将会得到显著不同的结果。     

分层流体中内孤立波在台阶上的反射和透射

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.     

双重孔隙流体饱和介质弹性波散射二维IBIEM模拟

基于平面波势函数,采用间接边界积分方程法(indirect boundary integral equation method, IBIEM)研究了双孔隙流体饱和介质中弹性波入射下二维孔洞的散射特性。推导得到了双孔隙介质中全空间二维线源动力格林函数,并给出了各散射波的位移场和应力场。在数值精度验证的基础上,以双孔隙二维饱和全空间中孔洞为例,解决了平面P、SV波入射下的地震波散射问题。数值结果表明：双重孔隙介质中的位移幅值、环向应力幅值、孔隙压力变化规律与不同入射波形,入射频率,孔隙率和边界排水条件密切相关,位移幅值在低频(无量纲频率η≤2)入射时出现峰值。环向应力幅值与干土条件相比更为复杂,基质孔压与裂缝孔压的存在增大了双重孔隙饱和介质的能量效应,总体震动趋势大于干土条件,环向应力放大可达62%。     

平面波在双孔隙介质中球形夹杂上的散射

基于拓展的Biot孔隙介质弹性理论,将波函数展开法推广应用到求解平面压缩波在双孔隙介质中单球形理想流体夹杂上的散射问题中.在低频条件下,给出了问题解析解的形式,包括位移场和应力场.由进一步的数值计算结果可知:P1波和S波的一阶谐波振幅随着基质孔隙率的增大而减小,P2波的谐波振幅则增大,而P3波的谐波振幅基本不受其影响;随着裂隙孔隙率的增大,P1波的谐波振幅逐渐减小,P3波和S波的谐波振幅增大,而对P2波的谐波振幅的影响甚微;频率越高,双孔隙介质的基质孔隙率及裂隙孔隙率对其谐波振幅的影响越显著.     

正交各向异性含液饱和多孔介质中应力波的传播

基于Biot的孔隙介质理论,研究了正交各向异性含液饱和多孔介质中应力波的传播特性．本文引入动态渗透率,导出了整个实频域内应力波传播的复特征方程及其解析解,给出了各种应力波成分的波速和衰减的解析表达武,计算了频散曲线和衰减曲线,并讨论了各类应力波之间的耦合关系及介质的各向异性对应力波传播的影响．     

Reflection and Transmission of Elastic Waves from the Interface of a Fluid-saturated Porous Solid and a Double Porosity Solid

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.     

Propagation of magnetoelastic shear waves across layers in a periodically layered medium

The paper is concerned with magnetoelastic shear waves propagating in regularly layered magnetostrictive media at a right angle to the layer interfaces __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 6, pp. 54–60, June 2006.     

Acoustic Waves in Channels with Porous and Permeable Walls

The propagation of acoustic disturbances in a porous medium crossed by numerous cracks (double porosity medium) is a complex problem that we here simplify by investigating the acoustics of a permeable channel. We consider a fluidfilled channel in two possible geometries, a slit or a cylindric pipe. The channel is surrounded by a porous medium (saturated with the same fluid) and is itself surrounded by an external medium. To simulate the average properties of the cracked rock, the external medium is either nonpermeable (few connections between cracks) or highly permeable (numerous connections). We present analytical and numerical results concerning acoustic disturbances of small amplitude generated in the channel, such as harmonic waves, step disturbanses and pulses.     

粘弹性Hopkinson压杆中波的衰减和弥散

研究了线性粘弹性Hopkinson压杆中由于粘性效应和横向惯性效应引起的应力波衰减和弥散.导出计及横向惯性效应的线性粘弹性杆中纵波控制方程和应力解应变解,进而导出表征波衰减和弥散性质的纵波传播系数的修正公式.这一修正公式计入粘性效应和几何效应,与Bacon公式相比,其形式简单,更便于在实验数据处理中应用.最后利用实验方法测定了有机玻璃杆的传播系数.     

结构中弹性波传播的可视化方法

由于结构中弹性波传播的复杂性,其场量(位移、应变、速度)表达式往往为繁杂、冗长的数学表达式,表达式本身不能直观、形象地表征结构中弹性波的传播特征．本文以杆中纵波传播为例,基于Matlab开发了弹性波传播特征的可视化程序,将杆中纵波传播特性以一种动态、直观、形象的形式展现出来．     

横观各向同性液体饱和多孔介质中平面波的传播

基于孔隙介质的Ｂｉｏｔ理论,研究了横观各向同性液体饱和多孔介质中平面波的传播特性．首先导出了波传播的特征方程并给出其解析解,结果显示：有４种不同波速的平面体波传播：第一准纵波（ＱＰ１）、第二准纵波（ＱＰ２）、准横波（ＱＳＶ）和反平面横波（ＳＨ）．文中给出了波速和衰减的解析表达式,数值计算了频散曲线和衰减曲线,并讨论了各类准体波位移之间的耦合关系．最后分析了Ｒａｙｌｅｉｇｈ波的生成条件和传播特性．文章详细讨论了介质异性对波传播特性的影响     

Reflection and transmission of obliquely incident Rayleigh surface waves by a viscoelastic interphase

The reflection and transmission of obliquely incident Rayleight surface waves by an interphase between two quarter spaces of identical or different materials, have been investigated. The mechanical behavior of the interphase is represented by a thin viscoelastic layer. By using the full space Green's functions due to a spatially harmonic line load, the mathematical statement of the 3-dimension problem is reduced to a 2-dimension system of singular integral equations. The far-field behavior of the scattered waves leads to the definition of reflection and transmission coefficients,R andT. The system of the singular integral equations are solved forR andT with the boundary element method. The results are presented for selected values of the elastic constants of the joined quarter spaces, the parameters of the interphase and the incident angles of Rayleigh surface waves.     

Exact solution of sound reflection on infinite laminated plate and transmission through it

An exact solution is proposed in this paper based on the elasticity theory for sound reflection from an infinite laminated plate and transmission through it, and some phenomena of sound propagation in an isotropic media are also discussed. Some examples given here could be used to test approximate models of laminated plates.