A mathematical model of shear wave propagation in the incompressible transversely isotropic thermoelastic half-spaces

This article deals with the problem of reflection and transmission of shear waves at a plane interface between two dissimilar incompressible transversely isotropic thermoelastic half-spaces. Two coupled quasi-shear waves are found to propagate due to the incompressibility of such materials. Applying appropriate boundary conditions at the plane interface, amplitude ratios of the reflected and transmitted quasi-shear waves are obtained. It has been observed that these ratios are functions of the angle of incidence, elastic and thermal parameters of the materials. These ratios are computed numerically for a particular model to see the effects of specific heat and thermal expansion on quasi-shear waves in incompressible transversely isotropic thermoelastic materials. The results are also presented graphically

The reflection coefficient from interface layers in NDT of adhesive joints.

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Wave Propagation Through a Micropolar Slab Sandwiched by Two Elastic Half-Spaces

The problem of wave propagation through a micropolar elastic slab sandwiched by two classical elastic half-spaces is studied in this paper. Different from the classical elastic solids, the particle in micropolar solids can bear not only the displacements but also the rotations. The additional kinetic freedom results in four kinds of wave modes, namely, the longitudinal displacement (LD) wave, the longitudinal microrotational (LR) wave, and two coupled transverse (CT) waves. Apart from the LD wave, the other three waves are dispersive. The existence of couple stresses and the microrotations also makes the interface conditions between the micropolar slab and the classic elastic half-spaces different from that between two classic solids. The nontraditional interface conditions lead to a set of algebraic equations from which the amplitude ratios of reflection and transmission waves can be determined. Further, the energy fluxes carried by various waves are evaluated and the energy conservation is checked to validate the numerical results obtained. The influences of the micropolar elastic constants and the thickness of slab are discussed based on the numerical results. Two situations of incident P wave and incident SH wave are both considered

Spherical wave reflection and transmission

This study is concerned with the reflection and transmission of spherical waves at a plane interface between two different media. The phenomenon of the reflection and transmission of spherical waves has been studied by means of analytical methods, numerical computation, and experimental tests. A new integral representation for a spherical wave is obtained by transforming Lamb/Sommerfeld's integral representation. The new integral has no singularity so it allows more accurate numerical integration. A new proof of Lamb/Sommerfeld's integral representation for a spherical wave is presented based on the new integral. By using the new form of solutions for reflected waves and existing solutions for transmitted waves, numerical studies have been carried out to examine. the phenomenon of reflection and transmission. of spherical waves at plane surfaces of discontinuity in material properties. It is shown that the effective critical angle for the total reflection of a spherical wave is greater than that of a plane wave at a hard boundary, and that when the source height increases the effective critical angle for the total reflection of a spherical wave tends to that of a plane wave. It is shown that recent predictions of spherical wave reflection and transmission coefficients greater than 1 at normal incidence under certain condition are probably due to numerical integration error. It also has been found that for spherical wave reflection and transmission, the time average energy flux, normal to a plane parallel to the plane of discontinuity, may locally be in the direction opposite to that of the direction of energy transmission over the plane as a whole. This so-called "backward wave" occurs in an interference between the direct and reflected waves, as well as in a transmitted wave. An indirect test on the theory has been performed to check the pressure field, above a rigid boundary, predicted by the spherical wave theory. Theoretical and experimental results were in good agreement

The application of ultrasonic NDT techniques in tribology

The use of ultrasonic reflection is emerging as a technique for studying tribological contacts. Ultrasonic waves can be transmitted non-destructively through machine components and their behaviour at an interface describes the characteristics of that contact. This paper is a review of the current state of understanding of the mechanisms of ultrasonic reflection at interfaces, and how this has been used to investigate the processes of dry rough surface contact and lubricated contact. The review extends to cover how ultrasound has been used to study the tribological function of certain engineering machine elements

Seismoelectric response of 2D elastic/poroelastic coupled media: a phenomenological approach

In this paper, we address the study of the seismoelectric response of an elastic medium in contact with a poroelastic half-space. In particular, we advance in the understanding of the generation mechanism of the interface response (IR) and the evanescent electromagnetic (EM) fields occurring at the contact between both media, by proposing a seismoelectric phenomenological model (SPM). Essentially, the model consists of a sequence of electric dipoles that are activated successively, simulating the seismic-to-EM energy conversion taking place with the arrival of a seismic wave at the interface separating the media. We obtained SPM responses for different scenarios and acquisition configurations and compared them with responses computed using a code based on the finite-elements method, which solves the seismoelectric equations in the compressional P and vertical shear SV waves coupled with the transverse-magnetic (TM) fields (PSVTM) mode. The SPM successfully represents not only the evanescent wave but also the IR within the elastic medium. In particular, we show that the SPM is able to faithfully reproduce the relative amplitudes of both events and their radiation patterns with a minimum computational cost. In this way, it provides a novel insight in the study of the physical phenomenon behind the seismoelectric conversions.Fil: Bucher, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Geofísica Aplicada; ArgentinaFil: Monachesi, Leonardo Bruno. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Castromán, Gabriel Alejandro. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Geofísica Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Zyserman, Fabio Ivan. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Geofísica Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin