• Geomechanics and Engineering
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• 제16권4호
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• pp.363-373
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• 2018

The evaluation of Thermo-Hydro-Mechanical (THM) coupling behavior is important for the development of underground space for various purposes. For a high-level radioactive waste repository excavated in a deep underground rock mass, the accurate prediction of the complex THM behavior is essential for the long-term safety and stability assessment. In order to develop reliable THM analysis techniques effectively, an international cooperation project, Development of Coupled models and their Validation against Experiments (DECOVALEX), was carried out. In DECOVALEX-2015 Task B2, the in situ THM experiment that was conducted at Horonobe Underground Research Laboratory(URL) by Japan Atomic Energy Agency (JAEA), was modeled by the research teams from the participating countries. In this study, a THM coupling technique that combined TOUGH2 and FLAC3D was developed and applied to the THM analysis for the in situ experiment, in which rock, buffer, backfill, sand, and heater were installed. With the assistance of an artificial neural network, the boundary conditions for the experiment could be adequately implemented in the modeling. The thermal, hydraulic, and mechanical results from the modeling were compared with the measurements from the in situ THM experiment. The predicted buffer temperature from the THM modelling was about $10^{\circ}C$ higher than measurement near by the overpack. At the other locations far from the overpack, modelling predicted slightly lower temperature than measurement. Even though the magnitude of pressure from the modeling was different from the measurements, the general trends of the variation with time were found to be similar.

• 한국응용과학기술학회지
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• 제33권1호
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• pp.168-175
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• 2016

유리섬유 번들의 인장강도와 복합재료의 매트릭스수지인 페놀수지와의 접착성을 향상시키기 위하여 관능기를 가진 실란 커플링제와 페놀 수지를 이용하여 표면을 개질하였다. 일반적으로 보강재인 유리섬유의 표면을 화학적으로 개질하므로 복합재료의 특성을 조절할 수 있다. 본 연구에서는 에폭시계인 glycidyltrimethoxysilane(G-silane)과 아미노계 aminopropyltriethoxysilane (A-silane)과 페놀 수지를 사용하여 여러 농도와 온도에서 유리섬유 표면에 1단계 처리 및 2단계 복합처리를 수행하였다. 이 때 열처리 조건이 인장강도를 향상시키는 데 가장 중요하였다. 즉 $170^{\circ}C$에서 처리된 유리섬유의 인장강도가 $10.05g_f/D$로 최대를 나타내었다. 개질 후의 유리섬유 표면은 전자현미경과 적외선분광법을 이용하여 분석하였다. 실란의 종류와 처리 조건에 따른 유리 섬유 기계적 강도에 관한 영향도 고찰하였다.

• Geomechanics and Engineering
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• 제13권1호
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• pp.63-77
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• 2017

The failure mechanism of a deep hard rock tunnel under high geostress and high geothermalactivity is extremely complex. Uniaxial compression tests of granite at different temperatures were conducted. The complete stress-strain curves, mechanical parameters and macroscopic failure types of the rock were analyzed in detail. The brittleness index, which represents the possibility of a severe brittleness hazard, is proposed in this paperby comparing the peak stress and the expansion stress. The results show that the temperature range from 20 to $60^{\circ}C$ is able to aggravate the brittle failure of hard rock based on the brittleness index. The closure of internal micro cracks by thermal stress can improve the strength of hard rock and the storage capacity of elastic strain energy. The failure mode ofthe samples changes from shear failure to tensile failure as the temperature increases. In conclusion, the brittle failure mechanism of hard rock under the action of thermal coupling is revealed, and the analysis result offers significant guidance for deep buried tunnels at high temperatures and under high geostress.

• 한국연소학회지
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• 제21권2호
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• pp.29-37
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• 2016

This study described the experimental investigations of combustion instability in a model gas turbine combustor. Strong coupling between pressure oscillations and unsteady heat release excites a self-sustained acoustic wave, which results in a loud and annoyed sound, and may also lead to a structural damage to the combustion system. In this study, in order to examine the combustion instability phenomenon of a dual swirling combustor configuration, the information of heat release and pressure fluctuation period with respect to the variation in both thermal power and combustor length was collected experimentally. As a result, the fundamental acoustic frequency turned out to increase with the increasing thermal power without respect to the combustor length. The frequency response to the combustor length was found to have two distinct regimes. In a higher power regime the frequency significantly decreases with the combustor length, as it is expected from the resonance of gas column. However, in a lower power regime it is almost insensitive to the combustor length. This insensitive response might be a result of the beating phenomenon between the interacting pilot and main flames with different periods.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1207-1212
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• 2004

A model for the phonon dispersion relationship for cubic zinc sulfide structure, for example SiC, is developed in terms of two unknown force constants. Born model that incorporates bond bending and bond stretching, is used for the force constants. The force constants are determined by fitting to experimental data. Using only the nearest-neighbor coupling results in $6{\times}6$ sized dynamic matrix. The eigenvalues of dynamics matrix for each wavenumber in 3-D ${\kappa}$ space correspond to frequencies, 3 for optical phonon and 3 for acoustic phonon, which is so-called dispersion relation (${\kappa}$-${\omega}$). The density of state is determined by counting the states for each frequency bin, and the properties such as specific heat and thermal conductivity can be obtained. The specific heat is estimated on this model and compared with experiment and other models, i.e. Debye model, Einstein model and combined Debye-Einstein model. In spite of the simple bond potential model, reasonable agreements are found.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2010년도 춘계 학술논문 발표대회 1부
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• pp.219-220
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• 2010

The purpose of this study is to evaluate chloride ion attack durability of concrete structure having experienced the high temperature fire. Mechanical properties and anti chloride ion diffusivity of concrete specimens were measured which have experienced of 2 hours heating at $200{^{\circ}C},\;400{^{\circ}C},\;600{^{\circ}C},\;800{^{\circ}C}$. The coupling FE model of thermal transfer and chloride ion diffusion was built to predict the life expectancy of RC structure using the property values by a series of experiment.

• Coupled systems mechanics
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• 제7권1호
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• pp.5-25
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• 2018

A fully-coupled thermodynamic-based transient finite element formulation is proposed in this article for electric, magnetic, thermal and mechanic fields interactions limited to the linear case. The governing equations are obtained from conservation principles for both electric and magnetic flux, momentum and energy. A full-interaction among different fields is defined through Helmholtz free-energy potential, which provides that the constitutive equations for corresponding dual variables can be derived consistently. Although the behavior of the material is linear, the coupled interactions with the other fields are not considered limited to the linear case. The implementation is carried out in a research version of the research computer code FEAP by using 8-node isoparametric 3D solid elements. A range of numerical examples are run with the proposed element, from the relatively simple cases of piezoelectric, piezomagnetic, thermoelastic to more complicated combined coupled cases such as piezo-pyro-electric, or piezo-electro-magnetic. In this paper, some of those interactions are illustrated and discussed for a simple geometry.

• 터널과지하공간
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• 제9권4호
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• pp.282-283
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• 1999

핵폐기물 지하처분, 지열개발, 지하 환경의 안전과 제어 등과 관련된 문제에 있어서 암석 및 암반의 역학적 거동 외에 열·수리·화학적 상호작용에 대한 이해가 필요하다. 이미 전세계적으로 국가별로 혹은 공동연구를 통하여 열·수리·역학적 상호작용에 관하여 많은 연구가 진행되었으며 최근 화학적 상호작용에 대한 문제가 추가적으로 제기되고 있다. 특히 장기간의 지하 환경의 안정성에 미치는 중요한 요소로 크립현상과 열·수리 화학적 상호작용 연구에 대한 필요성이 제기된 바 있다. 이 중 열·역학적 상호작용에 대해서는 현장문제에 적용 가능한 만은 연구결과가 제시된 바 있으나 기타 상호작용에 대해서는 다양한시험방법과모델링으로 인하여 아직가지 통일된 의견이 제시된 바 없다. 제 2주제에는 총 92편의 논문이 접수되었으며, 이 논문들의 내용, 성격, 해석방법 등을 간략히 정리하였다.

• 열처리공학회지
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• 제8권3호
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• pp.213-221
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• 1995

Temperature distribution, transformation and residual stresses generated during the quenching process of carbon steel. It follows many difficulties in the analytical considerations on those quenching process because of the coupling effects on temperature and metallic structures. In this paper one of the basic study on the quenching stresses was carried out for the case of the round steel bar specimen(SM45C) with 40mm both in its diameter and length. The temperature distributions considering strain hysteresis were numerically calculated by finite element technique. In calculating the transient temperature field, the heat flux between water and rod surface was determined from the heat transfer coefficient. The gradient of temperature is almost same to geometric of specimen. At early stage of the quenching process, the abrupt temperature gradient has been shown in the surface of the specimen.

• 대한기계학회논문집
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• 제18권2호
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• pp.456-466
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• 1994

Experimental investigation was made to study the mechanism of fluid and thermal oscillation phenomena of surface-tension driven flow in a cylindrical liquid column heated from above which is the low-gravity floating zone simulated on earth. Hexadecane, octadecane, silicon oil (10cs), FC-40 and water are used as the test liquids. The onset of the oscillatory thermocapillary convection appears when Marangoni number exceeds its criteria value and is found to be due to the coupling among velocity and temperature field with the free surface deformation. The frequency of temperature oscillation decreases with increasing aspect ratio for a given diameter and Marangoni number and the oscillation level increases with Marangoni number. The flow pattern in the liquid column appears either as symmetric or asymmetric 3-D flow due to the oscillatory flow in the azimuthal direction. The free surface deformation also occurs either as symmetric or asymmetric mode and its frequency is consistent with those of flow and temperature oscillations. The amplitude of surface deformation also increases with Marangoni number.