• 한국농공학회논문집
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• 제62권4호
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• pp.45-51
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• 2020

The poisson's ratio was obtained from the effective vertical stress and horizontal stress of consolidation-undrained test. It was analyzed void ratio verse poisson's ratio. At the result, the effective friction angle was increase with relative density increased, was decreased the poisson's ratio. The empirical equation of void ratio and poisson's ratio was showed very high correlation r²=0.846. The empirical equation was showed that the smaller the void ratio in the fine grained soil than granular soil. In the case of 0.85 times the correlation analysis equation of granular and fine grained soil, the experimental results were shown very similarly. In especially, the poisson's ratio prediction results was shown within 5% of the error range, was revalidation 0.85 times the correlation analysis equation using the void ratio. In this study, correlation analysis equation of the granular and fine grained soil was more reliability of the poisson's ratio prediction results apply to the void ratio than dry unit weight.

• 한국도로학회논문집
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• 제3권1호
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• pp.185-197
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• 2001

본 연구는 온도에 따라 특성이 변하는 아스팔트 콘크리트의 파괴인성을 규명하기 위하여 기존의 유효균열 모델을 수정하는 연구를 다루고 있다. 본래의 ECM모델은 콘크리트와 같은 고체에 적용되도록 개발되어 재료의 포아슨 비를 고려하지 않는다. 하지만 아스팔트 콘크리트는 온도변화에 민감하여 온도에 따라 포아슨 비가 변화하므로 다양한 온도하에서 정확한 파괴 특성을 알기 위해서는 포아슨 비가 고려되어져야 한다. 3개의 개질아스팔트 결합재를 포함한 4가지 결합재를 사용하여 밀입도 아스팔트 혼합물을 제조하여 초기균열 보에 대한 3점 휨 시험을 $-5^{\circ}C$부터 $-35^{\circ}C$까지에서 수행하였다. 탄성계수, 휨강도 및 파괴인성을 시험을 통하여 구하였다. 시험결과 포아슨비가 고려되는 수정 ECM 공식을 사용하므로서 보다 정확한 값들을 얻을 수 있었다. 폴리머 개질 아스팔트 혼합물이 일반아스팔트 혼합물에 비하여 더 낮은 저온하에서 더 높은 강성과 파괴인성을 유지함을 알 수 있었다.

• Journal of Mechanical Science and Technology
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• 제19권12호
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• pp.2224-2230
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• 2005

In this study, the validity of the Eshelby-type model for predicting the effective Young's modulus and in-plane Poisson's ratio of the 2-dimensional perforated plate has been investigated in terms of the porosity size and its arrangement. The predicted results by the Eshelby-type model are compared with those by finite element analysis. Whenever the ratio of the porosity size to the specimen size becomes smaller than 0.07, the effective elastic constants predicted by finite element analysis are convergent regardless of the arrangement of the porosities. Under these conditions, the effective Young's moduli of the perforated plate can be predicted within the accuracy of $5\%$ by the Eshelby-type model, which overestimates and underestimates the effective Poisson's ratios by $10\%\;and\;6\%$ for the plates with periodically and non-periodically arranged porosities, respectively.

• 대한기계학회논문집A
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• 제32권9호
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• pp.713-719
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• 2008

Most of the MEMS parts are made of multi-grain silicon wafer, which is the orthotropic material and its material direction is arbitrary. The reliability of the parts must be guaranteed in order to use for the commercial usage. The need of the structural analysis of its parts emerges an important factor. The material properties of the MEMS parts are calculated by the numerical method in order to reduce a material test. In this study, the effective elastic modulus and its Poisson's ratio are calculated by the boundary element method(BEM) and are compared with the results by the finite element method(FEM).

• 대한조선학회지
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• 제22권1호
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• pp.45-53
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• 1985

For the analysis of vertical vibrations of a ship's hull, the Timoshenko beam analogy is accepted up to seven or eight-node modes provided that the system parameters are properly calculated. As to the shear coefficient, it has been a common practice to apply the strain energy method or the projected area method. The theoretical objection to the former is that it ignores lateral contraction due to Poisson's ratio, and the latter is of extreme simplifications. Recently, Cowper's and Stephen's shear coefficient formulas have drawn ship vibration analysts' attentions because these formulas, derivation of which are based on an integrations of the equations of three-dimensional elasticity, take Poisson's ratio into account. Providing computer programs for calculation of the shear coefficient of ship sections modeled as thin-walked multicell sections by each of the forementioned methods, the authors calculated natural vibration characteristics of a bulk carrier and of a container ship by the transfer matrix method using shear coefficients obtained by each of the methods, and discussed the results in comparision. The major conclusions resulted from this investigation are as follows: (1) The shear coefficients taking account of the effects of Poisson's ratio, Cowper's $K_c$ and Stephen's $K_s$, result in higher values of about 10% in maximum as compared with the shear coefficient $K_o$ based on the conventional strain energy methods; (a) $K_c/K_o{\cong}1.05\;and\;K_s/K_o{\cong}1.10$ for ships having single skin side-shell such as a bulk carrier. (b) $K_c/K_o{\cong}1.02\;and\;K_s/K_o{\cong}1.05$ for ships having longitudinally through bulkheads and/or double side-shells in the portion of the cargo hod such as a container carrier. (2) The distributions of the effective shear area along the ship's hull based on each of $K_o,\;K_c\;and\;K_s$ are similar each another except the both end portions. (3) Natural frequencies and mode shapes of the hull based on each of $K_c\;and\;K_s$ are of small differences as compared each other. (4) In cases of using $K_c\;or\;K_s$ in ship vibration analysis, it is also desirable to have the bending rigidity be corrected according to the effective breadth concept. And then, natural frequencies and mode shapes calculated with the bending rigidity corrected in the above and with each of $K_o,\;K_c\;and\;K_s$ result in small differences as compared each another. (5) Referring to those mentioned in the above (3) and (4) and to the full-scale experimental results reported by Asmussen et al.[17], and considering laboursome to prepare the computer input data, the following suggestions can safely be made; (a) Use of $K_o$ in ship vibration analysis is appropriate in practical senses. (b) Use of $K_c$ is appropriate even for detailed vibration analysis of a ship's hull. (6) The effective shear area based on the projected area method is acceptable for the two-node mode.

• 한국정밀공학회지
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• 제28권11호
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• pp.1288-1296
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• 2011

Effective elastic constants of bone-like biocomposites are investigated numerically. The bone-like materials are composed of strong layers and weak layers, and hierarchically structured. The unit cell model is employed to obtain the effective elastic constants. The effective anisotropic elastic constants of bone-like composites are obtained by using the potential energy method and finite element analysis. The effects of the Poisson's ratio, elastic modulus, hierarchical level, volume fraction and aspect ratio of the strong layer composed of the composites on the effective elastic constants are discussed.

• 한국지반공학회논문집
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• 제30권5호
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• pp.67-75
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• 2014

본 연구에서는 벤더엘리먼트가 장착된 삼축시험장비를 이용하여 모래에 대한 일련의 압밀배수시험을 수행하여 응력, 변형률, 그리고 전단파속도를 측정하였으며 이로부터 전단강도와 포아송비의 특성을 분석하였다. 분석 결과, 전단파속도로부터 계산된 최대전단탄성계수와 파괴시의 축응력과 반경방향 응력의 합으로 정의되는 유효수직응력과는 고유한 상관관계가 존재하는 것으로 나타났다. 도출된 경험식은 전단파속도와 전단강도 그리고 마찰각간의 상관관계를 나타내므로 매우 유용하다고 판단된다. 나아가 본 연구에서는 측정된 축변형률과 체적변형률로부터 모래의 포아송비를 측정하였다. 포아송비는 변형률과 체적변화에 큰 영향을 받으며 0.15~0.6까지 변형률에 따라서 크게 증가하는 것으로 나타났다. 특히 0.2% 미만의 축변형률에서는 대략 0.25~0.4으로 기존 문헌에서 제시된 0.3~0.35를 크게 벗어나지 않지만 1% 이상의 변형률에서는 0.5~0.6으로 문헌에서 제시된 값은 포아송비를 크게 과소예측하는 것으로 나타났다.

• Geomechanics and Engineering
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• 제7권4호
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• pp.403-430
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• 2014

Shale gas formations exhibit strong mechanical and strength anisotropies. Thus, it is necessary to study the effect of anisotropy on the hydraulic fracture initiation pressure. The calculation model for the in-situ stress of the bedding formation is improved according to the effective stress theory. An analytical model of the stresses around wellbore in shale gas reservoirs, in consideration of stratum dip direction, dip angle, and in-situ stress azimuth, has been built. Besides, this work established a calculation model for the stress around the perforation holes. In combination with the tensile failure criterion, a prediction model for the hydraulic fracture initiation pressure in the shale gas reservoirs is put forward. The error between the prediction result and the measured value for the shale gas reservoir in the southern Sichuan Province is only 3.5%. Specifically, effects of factors including elasticity modulus, Poisson's ratio, in-situ stress ratio, tensile strength, perforation angle (the angle between perforation direction and the maximum principal stress) of anisotropic formations on hydraulic fracture initiation pressure have been investigated. The perforation angle has the largest effect on the fracture initiation pressure, followed by the in-situ stress ratio, ratio of tensile strength to pore pressure, and the anisotropy ratio of elasticity moduli as the last. The effect of the anisotropy ratio of the Poisson's ratio on the fracture initiation pressure can be ignored. This study provides a reference for the hydraulic fracturing design in shale gas wells.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.2000-2010
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• 2021

Mechanical moduli, such as Young's modulus (E), Bulks modulus (B), Shear modulus (S), longitudinal modulus (L), Poisson's ratio (σ) and micro Hardness (H) were theoretically calculated for (100-x)TeO₂+x MgO glasses, where x = 10, 20, 30, 40 and 45 mol%, based on the Makishima-Mackenzie model. The estimated results showed that the mechanical moduli and the microhardness of the glasses were improved with the increase of the MgO contents in the TM glasses, while Poisson's ratio decreased with the increase in MgO content. Moreover, the radiation shielding capacity was evaluated for the studied TM glasses. Thus, the linear attenuation coefficient (LAC), mass attenuation coefficient (MAC), transmission factor (TF) and half-value thickness (𝚫_0.5) were simulated for gamma photon energies between 0.344 and 1.406 MeV. The simulated results showed that glass TM10 with 10 mol % MgO possess the highest LAC and varied in the range between 0.259 and 0.711 cm^-1, while TM45 glass with 45 mol % MgO possess the lowest LAC and vary in the range between 0.223 and 0.587 cm^-1 at gamma photon energies between 0.344 and 1.406 MeV. Furthermore, the BXCOM program was applied to calculate the effective atomic number (Z_eff), equivalent atomic number (Z_eq) and buildup factors (EBF and EABF) of the glasses. The effective removal cross-section for the fast neutrons (ERCSFN, ∑_R) was also calculated theoretically. The received data depicts that the lowest ∑_R was achieved for TM10 glasses, where ∑_R = 0.0193 cm² g^-1, while TM45 possesses the highest ERCSFN where ∑_R = 0.0215 cm² g^-1.

• 대한기계학회논문집
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• 제15권2호
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• pp.611-617
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• 1991

Effective stiffness of short fiber composite with a three-dimensional random orientation of fibers is derived theoretically and compared with available experimental data. The laminate analogy and transformed laminate analogy are used for modulus prediction of 2-D and 3-D random composites, respectively. The effective stiffness of random oriented fiber composite can be expressed in terms of longitudinal and transverse stiffnesses of unidirectional composites. The result of transformed laminate analogy is more accurate than other approaches such as, Christensen-Waals equational and Lavengood-Goettler equation, etc. Also the effective properties of random oriented fiber composite can be expressed in terms of fiber and matrix properties such as elastic modulus, shear modulus and Poisson's ratio.