• Geomechanics and Engineering
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• v.14 no.1
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• pp.19-27
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• 2018

It follows from the basic principles of mechanics of deformable solids relating to the strength, stability and propagation of elastic waves that the Earth's inner core cannot exist in the form of a spherical structure in the assumed thermobaric conditions and calculation values of physico-mechanical parameters. Pressure level reaches a value that is significantly greater than the theoretical limit of medium strength in the model approximations at the surface of the sphere of the inner core. On the other hand, equilibrium state of the sphere is unstable on the geometric forming at much lower loads under the influence of the "dead" surface loads. In case of the action of "follower" loads, the assumed pressure value on the surface of the sphere is comparable with the value of the critical load of "internal" instability. In these cases, due to the instability of the equilibrium state, propagation of homogeneous deformations becomes uneven in the sphere. Moreover, the elastic waves with actual velocity cannot propagate in such conditions in solid medium. Violation of these fundamental conditions of mechanics required in determining the physical and mechanical properties of the medium should be taken into account in the integrated interpretations of seismic and laboratory (experimental) data. In this case, application of the linear theory of elasticity and elastic waves does not ensure the reliability of results on the structure and composition of the Earth's core despite compliance with the required integral conditions on the mass, moment of inertia and natural oscillations of the Earth.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.3
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• pp.296-307
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• 2010

This paper deals with the energy transmission ratio of the elastic waves transmitting through a solid wall. Based on the displacement of the reflected and transmitted waves relative to the incident waves, the energy transmission ratio of the wave was obtained by multiplying the vibration velocity and stresses. Numerical calculation provided with the transmission ratio and refraction angle corresponding to the incidence angle, and it showed the mode conversion from the incident longitudinal wave to the transmitted transverse wave in particular incidence angle range. The paper established a procedure to find the incidence angle of the maximum energy transmission ratio and confirmed it by experiment.

• Journal of KSNVE
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• v.8 no.6
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• pp.1172-1180
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• 1998

Elastic wave scattering from an acoustically rigid or soft object is studied and compared with the acoustic wave scattering. The behavior of phases as well as magnitudes of partial waves and their total summation of scattered wave are numerically analyzed and discussed. The effect of mode conversion, which occurs between longitudinal and transversal waves in elastic wave scattering. on the magnitudes and phases of scattered waves is identified.

• Structural Engineering and Mechanics
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• v.66 no.1
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• pp.113-124
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• 2018

In the present paper, we have considered a layered medium of two semi-infinite nonlocal elastic solids with intermediate transversely isotropic magnetothermoelastic solid. The intermediate slab is of uniform thickness with the effects of two temperature, rotation and Hall current and with and without energy dissipation. A plane longitudinal or transverse wave propagating through one of the nonlocal elastic solid half spaces, is made incident upon transversely isotropic slab and it results into various reflected and refracted waves. The amplitude ratios of various reflected and refracted waves are obtained by using appropriate boundary conditions. The effect of nonlocal parameter on the variation of various amplitude ratios with angle of incidence are depicted graphically. Some cases of interest are also deduced.

• Structural Engineering and Mechanics
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• v.82 no.4
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• pp.459-467
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• 2022

We investigated the influence of variable thermal conductivity on waves propagating through the elastic medium. Infinitesimal deformation results in generation of thermal signal, and is analyzed by using dual phase lag heat (DPL) conduction model. The medium considered is homogenous, isotropic and bounded by thermal shock. The elastic waves propagating through the medium are considered to be harmonic in nature, and expressions for the physical variables are obtained accordingly. Analytically, we obtained the expressions for displacement components, temperature, micro-temperature component and stresses. The theoretical results obtained are computed graphically for the particular medium by using MATLAB.

• Structural Engineering and Mechanics
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• v.85 no.3
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• pp.305-314
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• 2023

The article is about the theoretical analysis of the transmission and reflection of elastic waves through the interface of perfectly connected materials. The solid continuum mediums considered are piezoelectric semiconductors and transversely isotropic in nature. The connection among the mediums is considered in such a way that it holds the continuity property of field variables at the interface. The concept of strain and stress introduced by non-local theory is also being involved to make the study more applicable It is found that, the incident wave results in the generation of four reflected and three transmitted waves including the thermal and elastic waves. The thermal waves generated in the medium are encountered by using the concept of three phase lag heat model along with fractional ordered time thermoelasticity. The results obtained are calculated graphically for a ZnO material with piezoelectric semiconductor properties for medium M₁ and CdSc material with transversely isotropic elastic properties for medium M₂. The influence of fractional order parameter, non-local parameter, and steady carrier density parameter on the amplitude ratios of reflected and refraction waves are studied graphically by MATLAB.

• Journal of applied mathematics & informatics
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• v.5 no.3
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• pp.811-818
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• 1998

A cylindrical elastic layer in finite deformation s con-sidered. The characteristics of the linear longitudinal wave and the nonlinear shear wave are investigated; the dependence of the later on the parameter of large deformation is given.

• Geomechanics and Engineering
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• v.21 no.3
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• pp.227-236
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• 2020

Non-destructive exploration using elastic waves has been widely used to characterize rock mass properties. Wave propagation in jointed rock masses is significantly governed by the characteristics and orientation of discontinuities. The relationship between spatial heterogeneity (i.e., joint spacing) and wavelength for elastic waves propagating through jointed rock masses have been investigated previously. Discontinuous rock masses can be considered as an equivalent continuum material when the wavelength of the propagating elastic wave exceeds the spatial heterogeneity. However, it is unclear how stress-dependent long-wavelength elastic waves propagate through a repetitive rock-joint system with multiple joints. A preliminary numerical simulation was performed in in this study to investigate long-wavelength elastic wave propagation in regularly jointed rock masses using the three-dimensional distinct element code program. First, experimental studies using the quasi-static resonant column (QSRC) testing device are performed on regularly jointed disc column specimens for three different materials (acetal, aluminum, and gneiss). The P- and S-wave velocities of the specimens are obtained under various normal stress levels. The normal and shear joint stiffness are calculated from the experimental results using an equivalent continuum model and used as input parameters for numerical analysis. The spatial and temporal sizes are carefully selected to guarantee a stable numerical simulation. Based on the calibrated jointed rock model, the numerical and experimental results are compared.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.323-326
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• 1998

The paper describes a theoretical and experimental study on the speed of the torsional elastic waves propagating in an axisymmetirc waveguide whose cross-sectional area varies periodically as an harmonic function of the axial coordinate. The approximate solution of the phase speed has been obtained using the perturbation technique for sinusoidal modulation of small amplitude. The experiment verifying the theoretical result consists of transmitting and receiving torsional waves by magnetostriction and measuring the wave speed in the waveguides with threaded surfaces.

• The Journal of the Acoustical Society of Korea
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• v.19 no.1E
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• pp.3-12
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• 2000

In this paper, two major theories of effective medium for composite materials are studied, which provide the average dynamic mechanical properties of particulate composites carrying elastic waves on the basis of the concept of self-consistent scattering of waves. These two theories are also compared in detail with each other to delineate the difference in the underlying ideas and their limitation of applicability. Furthermore, prospective directions for potential improvement of the theories are found. Numerical results for three particulate composites are given and discussed.