• Tunnel and Underground Space
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• v.20 no.6
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• pp.455-464
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• 2010

The variations of the uniaxial compressive strength, the strains and the elastic constants with respect to the angle of anisotropy are analyzed in order to investigate the characteristics of a transversely isotropic rock experimentally. Total 35 specimens of 7 different angles from a large block of rhyolite presenting the flow structure obviously are used in tests. This study is composed of two reports; the elastic constants are mainly analyzed for the every individual angle in the report No. 1 and they will be discussed synthetically in the report No. 2. From the specimens of 0 and 90 degree, 4 independent elastic constants which can directly be obtained without the help of any other suggested equations, may be referred to the true values. Data variation in the strain measurements differs on the angle is analyzed. That of small angle specimens tends higher than that of large angle specimens. The relation of apparent Young’s modulus and angle is found to be M- or U-shaped. For small angle specimens, Saint-Venant approximation cannot be applied successfully on account of showing the non-monotonous increase, and E1 is analyzed out of the true value range. In the specimen of $\phi$ = 75, the deviation of strain measurement and strength are smallest and 4 all constants are analyzed in the true value range. Therefore, specimen of the angle of around 75 may become preferable if only one specimen should be used in test of a transversely isotropic rock.

• Geophysics and Geophysical Exploration
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• v.14 no.3
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• pp.191-202
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• 2011

Reserve-time migration (RTM) using a two-way wave equation is one of the most accurate migration techniques. RTM has been conducted by assuming that subsurface media are isotropic. However, anisotropic media are commonly encountered in reality. Conventional isotropic RTM may yield inaccurate results for anisotropic media. In this paper, we develop RTM algorithms for vertical transversely isotropic media (VTI) and tilted transversely isotropic media (TTI). For this, the pseudo-acoustic wave equations are used. The modeling algorithms are based on the high-order finite-difference method (FDM). The RTM algorithms are composed using the cross-correlation imaging condition or the imaging condition using virtual sources. By applying the developed RTM algorithms to the Hess VTI and BP TTI models, we could obtain better images than those obtained by the conventional isotropic RTM.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.121-126
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• 2008

A plane strain problem of a crack on interface between an isotropic elastic conductor and a transversely isotropic piezoelectric ceramics is considered. The problem is reduced to system integrodifferential equations on the interface. These equations relate the normal and tangential components of the crack opening vector with distribution of normal and shear stresses on the crack surfaces. It therefore make it possible to obtain an exact solution as a function of the loading applied to the crack surfaces. As an example, some analytical solutions of the crack problem are given.

• Tunnel and Underground Space
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• v.12 no.4
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• pp.237-247
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• 2002

A total of 18 stress measurements were performed in the rock and rock-like blocks in the laboratory to estimate the influence of anisotropy in rock. Full scale overcoring equipment, which consists of a coring machine and a biaxial loading system by flat jacks, was developed to simulate the in-situ rock stress condition in the laboratory By comparing the isotropic analysis with the anisotropic analysis in measuring the stress, conclusions have been drawn as to the influence of anisotropy. The maximum difference between the isotropic and the anisotropic analysis was 34% and it was shown that the stress measurement considering the anisotropy was needed. To confirm the validity of the observed data, a diagnostic analysis of stress relief curve by overcoring was conducted using the three dimensional finite difference program, FLAC 3D.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.155-156
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• 2011

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.6
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• pp.665-672
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• 2012

Interfacial cracks bonded with dissimilar transversely isotropic piezoelectric media that are subjected to combined anti-plane mechanical and in-plane electrical loading are analyzed. The problem is formulated using complex function theory, from which the Hilbert problem is derived. By solving the Hilbert problem, the general form solution is obtained. Using this solution, closed-form solutions for one or two finite cracks as well as a semi-infinite crack are obtained, for the problem in which one concentrated mechanical and electrical load is imposed on the crack surface. This solution could be used as a Green's function to generate solutions to other problems with the same geometry but different loading conditions.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.25-30
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• 2004

Unidirectional fiber-metal matrix composites have superior mechanical properties along the longitudinal direction. However, the applicability of continuous fiber reinforced MMCs is somewhat limited due to their relatively poor transverse properties. Therefore, the transverse properties of MMCs are significantly influenced by the properties of the fiber/matrix interface. In this study, the interfacial stress states of transversely loaded unidirectional fiber reinforced metal matrix composites investigated by using elastic-plastic finite element analysis. Different fiber volume fractions $(5-60\%)$ were studied numerically. The interface was treated as thin layer (with different properties) with a finite thickness between the fiber and the matrix. The fiber is modeled as transversely isotropic linear-elastic, and the matrix as isotropic elastic-plastic material. The analyses were based on a two-dimensional generalized plane strain model of a cross-section of an unidirectional composite by the ANSYS finite element analysis code.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.383-390
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• 2008

This paper presents the formulation and numerical implementation of a spectral scheme specially developed to simulate dynamic fracture events in unidirectional and cross-ply fiber-reinforced composites. The formulation is based on the spectral representation of the transversely isotropic elastodynamic relations between the traction stresses along the fracture plane and the resulting displacements. Example problem of dynamically propagating cracks in fiber-reinforced composites is investigated and compared with reference solutions available in the literature and/or experimental observations. This scheme can be directly applicable to the interfacial fracture analysis in the FRP reinforced concrete structures.

• 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.

• Tunnel and Underground Space
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• v.18 no.4
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• pp.252-262
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• 2008

In the uniaxial compressive test of a single specimen of transversely isotropic rock, its 5 independent elastic constants can not be defined since maximum 4 independent strain measurements are available theoretically. In order to solve this problem, one equation proposed by Saint Venant in 19C and confirmed by Lekhnitskii through the test experiences has been used for long time. Accordign to authors' experiences, however, this equation turned out to give erroneous elastic constants in some cases. Three new equations are suggested and their compatibilities are discussed in this paper. As the results of the analyses of the models, Lekhnitskii's suggested equation is effective for the specimen with the high dip angle whereas it results in the large erred output for that with dip angle less than $25{\sim}30$. It was found that the effectivenesses of three suggested equations and their compatibilities are subject to the dip angle and not to the amounts of elastic constants. Guide map to the selection of the compatible one of those suggested equations is presented as a result of the study.