• 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 the Korean Society for Precision Engineering
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• v.19 no.5
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• pp.81-88
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• 2002

An interface crack of a piezoelectric medium bonded between an elastic layer and a half-space is analyzed using the theory of linear piezoelectricity. Both out-of-plane mechanical and in-plane electrical loads are applied to the piezoelectric laminate. By the use of courier transforms, the mixed boundary value problem is reduced to a singular integral equation which is solved numerically to determine the stress intensity factors. Numerical analyses for various material combinations are performed and the results are discussed.

• Interaction and multiscale mechanics
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• v.6 no.1
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• pp.15-29
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• 2013

Phononic system composed of periodical elastic structures exhibit band gap phenomenon, and all elastic wave cannot propagate within the band gap. In this article, we consider one-dimensional binary materials which are periodically arranged as a 20-layered medium instead of infinite layered system for phononic system. The layered medium with finite dimension is subjected to a uniformly distributed sinusoidal loading at the upper surface, and the bottom surface is assumed to be traction free. The transient wave propagation in the 20-layered medium is analyzed by Laplace transform technique. The analytical solutions are presented in the transform domain and the numerical Laplace inversion (Durbin's formula) is performed to obtain the transient response in time domain. The numerical results show that when a sinusoidal loading with a specific frequency within band gap is applied, stress response will be significantly decayed if the receiver is away from the source. However, when a sinusoidal force with frequency is out of band gap, the attenuation of the stress response is not obvious as that in the band gap.

• Geomechanics and Engineering
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• v.32 no.4
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• pp.397-409
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• 2023

This study examines two traditional approaches (non-linear elastic and elasto-plastic) in association with 2D and 3D FEM analyses of a box-section pile embedded in sand. A particular emphasis is placed on stress singularities concerning both reentrant corners of the pile section and the resulting tension zones. From the experience gained in this study, non-linear elastic soil models are less restrictive when one considers stress singularities and their possible effects on convergence of the solution. At least for monotonic loading, when compared with field tests, non-linear elastic models yield better results than the plasticity ones. On the other hand, although elasto-plastic models are not limited to monotonic loading, they are much more sensitive to stress singularities. For this reason, a spherical elastic region is necessary at the pile tip to ensure convergence. Without this region, one must artificially impose an apparent cohesion to limit the tension stresses within a sand medium.

• Structural Engineering and Mechanics
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• v.60 no.3
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• pp.489-505
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• 2016

Sinusoidal shear deformation theory (SSDT) is developed here for dynamic buckling of functionally graded (FG) nano-plates. The material properties of plate are assumed to vary according to power law distribution of the volume fraction of the constituents. In order to present a realistic model, the structural damping of nano-structure is considered using Kelvin-Voigt model. The surrounding elastic medium is modeled with a novel foundation namely as orthotropic visco-Pasternak medium. Size effects are incorporated based on Eringen'n nonlocal theory. Equations of motion are derived from the Hamilton's principle. The differential quadrature method (DQM) in conjunction with Bolotin method is applied for obtaining the dynamic instability region (DIR). The detailed parametric study is conducted, focusing on the combined effects of the nonlocal parameter, orthotropic visco-Pasternak foundation, power index of FG plate, structural damping and boundary conditions on the dynamic instability of system. The results are compared with those of first order shear deformation theory and higher-order shear deformation theory. It can be concluded that the proposed theory is accurate and efficient in predicting the dynamic buckling responses of system.

• Structural Engineering and Mechanics
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• v.60 no.4
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• pp.615-631
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• 2016

In this paper, an analytical method for the Post-buckling response of cylindrical shells with spiral stiffeners surrounded by an elastic medium subjected to external pressure is presented. The proposed model is based on two parameters elastic foundation Winkler and Pasternak. The material properties of the shell and stiffeners are assumed to be continuously graded in the thickness direction. According to the Von Karman nonlinear equations and the classical plate theory of shells, strain-displacement relations are obtained. The smeared stiffeners technique and Galerkin method is used to solve the nonlinear problem. To valid the formulations, comparisons are made with the available solutions for nonlinear static buckling of stiffened homogeneous and un-stiffened FGM cylindrical shells. The obtained results show the elastic foundation Winkler on the response of buckling is more effective than the elastic foundation Pasternak. Also the ceramic shells buckling strength higher than the metal shells and minimum critical buckling load is occurred, when both of the stiffeners have angle of thirty degrees.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.166-173
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• 2000

This paper describes the method of evaluating the elastic modulus of soil medium by using the Retangular Plate Loading Test. The foundaton is considered to be the elastic half-space. The stiffness matrix of elastic half space is drived using Boussinesq's analytical soulution. A numerical examples are presented to verify the validity of this procedure. Also, the numerical results are compared with those of the existing study results. The procedure proposed in this theses can be applied to the design of concrete paving resting on the elastic foundation

• The Journal of Engineering Geology
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• v.32 no.1
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• pp.1-12
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• 2022

Based on the extended spatial mobilization plane (SMP) criterion, we present an elastic-brittle-plastic solution for an axisymmetric cylindrical tunnel. The influences of the intermediate principal compressive stress and material strain-softening behavior are considered. Closed-form formulas for the critical support force, radius of plastic zone, and distributions of stress and displacement in surrounding rock are proposed. The elastic-plastic solution based on SMP is compared with the Kastner solution to verify the credibility of the obtained elastic-plastic solution. The elastic-brittle-plastic solution following the SMP criterion and the current solution based on the Mohr-Coulomb criterion are also compared. The rock strain-softening rate and the intermediate principal stress affect the stability of the surrounding rock. The results provide guidance for optimizing the design of support systems for tunnels.

• Interaction and multiscale mechanics
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• v.4 no.2
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• pp.85-105
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• 2011

The influence of surface elasticity and surface residual stress on the elastic field of an isotropic nanoscale elastic layer of finite thickness bonded to a rigid material base is considered by employing the Gurtin-Murdoch continuum theory of elastic material surfaces. The fundamental solutions corresponding to buried vertical and horizontal line loads are obtained by using Fourier integral transform techniques. Selected numerical results are presented for the cases of a finite elastic layer and a semi-infinite elastic medium to portray the influence of surface elasticity and residual surface stress on the bulk stress field. It is found that the bulk stress field depends significantly on both surface elastic constants and residual surface stress. The consideration of out-of-plane terms of the surface stress yields significantly different solutions compared to previous studies. The solutions presented in this study can be used to examine a variety of practical problems involving nanoscale/soft material systems and to develop boundary integral equations methods for such systems.

• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.6
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• pp.1-15
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• 1974

In this paper, the SH mode of elastic surface waves which are used for delay lines of elastic surface wave is the cretically analysed. It is shown that the SH mode has very large electromechanical coupling factor and propagates on the surface with very small decaying coefficient into the medium. In the case of P2T-4, the depth cf piezoelectric medium that contains 80% of energy is 190 wavelengths. An elastic surface wave delay line is discussed from the view point of 2-port network. Center frequency is shifted by the ratio of transducer electrode width to gap between transducer ellcerodes when electromechanical coupling factor is large. Tempera _ore coefficients for bulk waves of LiNbO3 and LiTaO3 are also calculated and the minimum temperature coefficient value of delay time is 5.4X 10-6/$^{\circ}C$ ia the case of transverse wave propagating along Z axis on LiTaO3. Experimental data are in good agreement with theoretical values of the temperature coefficients of delay time for elastic surface waves propagating along X axis of 130$^{\circ}$ and 64$^{\circ}$ rotated Y cut planes of the LiNbO3.