• 한국공작기계학회논문집
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• 제13권2호
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• pp.112-119
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• 2004

This paper discussed on the effect of an internal damping on the stability of an elastic material subjected to dry friction force. Dry friction forces act tangentially at the contact surface between a moving belt and elastic material. The elastic material on a belt moving is modeled for simplicity into a cantilevered beam subjected to distributed follower force. In the analysis, the discretized equations derived according to finite element method are used. The impulse response of the beam are studied by the mode superposition method to observe the growth rate of the motion. It is found that the internal damping in cantilevered beam subjected to distributed follower force may act destabilizing.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.670-676
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• 2003

To investigate the group plugging effect the fluid-elastic instability analysis has been performed on various column and row number of the KSNP steam generator lutes. This study compares the stability ratio of the plugged tube with that of the intact one. The information on the thermal-hydraulic data of the steam generator have been obtained by using the ATHOS3-MOD1 code with and without the thermal energy transfer at the plugged region. Both of the boundary conditions of hot-leg temperature and feedwater mass flow rate are fixed for this investigation. From the results of this study the stability ratios inside the group plugging zone are decreased slightly. At the outside of group plugging zone, however, most of the stability ratios tend to be increased.

• Structural Engineering and Mechanics
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• 제57권2호
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• pp.357-367
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• 2016

This paper illustrates an experimental study on a self compacting polymer concrete called isobeton made of polyurethane foam and expanded clay. Several experiments were conducted to characterize the physic-mechanical properties of the considered material. Application of the Linear Elastic Fracture Mechanics (LEFM) and determining the toughness of two isobetons based on Belgian and Italian clay, was conducted to determine the stress intensity factor $K_{IC}$ and the rate of releasing energy $G_{IC}$. The material considered was tested under static and dynamic loadings for two different samples with $10{\times}10{\times}40$ and $10{\times}15{\times}40cm$ dimensions. The result obtained by the application of the Linear Elastic Fracture Mechanics (LEFM) shows that is optimistic and fulfilled the physic-mechanical requirement of the study.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권10호
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• pp.583-588
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• 2000

This paper presents the design and fabrication of micro electromagnetic vibration silicon elastic body characterized with small size, high efficiency and selective frequency bandwidth for Bio-MENS applications, such as implantable middle ear hearing aid. The presented electromagnetic vibration transducer that composed of wounded coil, permanent magnet and 4-beam cross type elastic body is fabricated by using of micromachining technology. The fabricated transducer has experimental characteristics, that is 5 nm/mA of an energy trasfer rate at the frequency range of 100∼2800 Hz. It has a size of $2{\times}2{\times}2.5\;mm^3$.

• 지질공학
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• 제32권3호
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• pp.389-399
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• 2022

Observations on the influence of the fluid infiltration on the breakdown pressure during laboratory hydraulic fracturing tests, along with an analysis of the applicability of the breakdown pressure prediction for cylindrical samples using Quasi-static and Linear Elastic Fracture Mechanics approaches were carried out. These approaches consider fluid infiltration through the so-called radius of fluid infiltration or crack radius, a parameter that is not a material property. Two sets of tests under pressurization rate controlled and injection rate controlled tests were used to evaluate the applicability of these methods. The difficulty of the estimation of the radius of fluid infiltration was solved by back calculating this parameter from an initial set of tests, and later, the obtained relationships were used to predict breakdown pressures for a second set of tests. The results showed better predictions for the injection rate than for the pressurization rate tests, with average errors of 3.4% and 18.6%, respectively. The larger error was attributed to differences in the testing conditions for the pressurization rate tests, which had different applied vertical pressures. On the other hand, for the tests carried out under constant injection rate, the Linear Elastic Fracture Mechanics solution reported lower errors compared to the Quasi-static solution, with values of 3% and 3.8%, respectively. Moreover, a sensitivity analysis illustrated the influence of the radius of fluid penetration or crack radius and the tensile strength on the breakdown pressure, suggesting a need for a careful estimation of these values. Then, the calculation of breakdown pressure considering fluid infiltration in cylindrical samples under triaxial conditions is possible, although larger data sets are desirable to validate and derive better relations.

• Structural Engineering and Mechanics
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• 제52권4호
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• pp.663-686
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• 2014

This paper deals with free vibration analysis of bidirectional functionally graded annular plates resting on a two-parameter elastic foundation. The formulations are based on the three-dimensional elasticity theory. This study presents a novel 2-D six-parameter power-law distribution for ceramic volume fraction of 2-D functionally graded materials that gives designers a powerful tool for flexible designing of structures under multi-functional requirements. Various material profiles along the thickness and in the in-plane directions are illustrated by using the 2-D power-law distribution. The effective material properties at a point are determined in terms of the local volume fractions and the material properties by the Mori-Tanaka scheme. The 2-D differential quadrature method as an efficient and accurate numerical tool is used to discretize the governing equations and to implement the boundary conditions. The fast rate of convergence of the method is shown and the results are compared against existing results in literature. Some new results for natural frequencies of the plates are prepared, which include the effects of elastic coefficients of foundation, boundary conditions, material and geometrical parameters. The interesting results indicate that a graded ceramic volume fraction in two directions has a higher capability to reduce the natural frequency than conventional 1-D functionally graded materials.

• 한국지반공학회논문집
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• 제18권6호
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• pp.83-101
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• 2002

탄성파는 지표면에 가까운 흙에 관한 중요한 정보를 공급한다. 흙특성 파악에 물리탐사기법의 원활한 적용을 위하여 탄성파인자와 흙특성과의 관계를 고찰하였다. 적용 예로서, 비포화토의 거동 및 특성을 전단파 시험을 통하여 알아보았다. 포화시료를 건조하면서 밴더엘리먼트를 사용하여 미소변형률 전단강성을 연속적으로 측정하였다. 비포화토에서는 모세관현상, 이온공유에 의한 접착, 세립자 이동에 의한 강화효과, 염 침전에 의한 시멘트결합과 같은 입자간 힘의 변화가 강성의 변화에 직접적으로 영향을 끼치는 것으로 나타났다. 비포화토의 시료를 교란함으로써 메니스커스의 회복에 대한 연구를 수행하였고, 비포화토에서 일어나는 여러 가지 현상들을 제시하였다.

• Elastomers and Composites
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• 제33권4호
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• pp.274-280
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• 1998

가황반응에 대한 반응차수, 반응속도상수 및 활성화에너지, 가교결합에 의한 가교밀도 및 탄성상수를 동일한 가황시스템하에서 실리카와 카본블랙을 함유한 SBR/BR 블렌드에 대하여 조사하였다. 반응차수는 충전제 종류에 관계없이 1차 반응이었으며, 카본블랙이 첨가된 배합고무는 실리카가 첨가된 배합고무보다 반응속도가 빠르게 나타났다. 그러나 활성화에너지는 충전제 종류 및 고무 블렌드 조성에 관계없이 일정하게 나타났다. 가교밀도 및 탄성상수는 고무와 카본블랙간의 강한 상호작용으로 인해 카본블랙이 첨가된 조성물에서 높게 나타났다. 한편, 고무 블렌드중 부타디엔 고무 함량이 증가할수록 가교밀도 및 탄성상수는 감소하였다. 가황고무중 결합 황 함량 비교결과, 실리카가 첨가된 조성물중 일정한 결합 황 함량은 반응시작 후 20분 후에 나타났으나, 카본블랙이 첨가된 조성물은 10분 후에 나타났다. 또한 실리카가 첨가된 조성물은 카본블랙이 첨가된 조성물에 비해 반응 유도시간($t_2$) 및 최적 가황시간($t_{90}$)이 길게 나타났다.

• 대한토목학회논문집
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• 제13권5호
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• pp.19-27
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• 1993

파괴역학에서 최근의 연구들은 균열체의 강도를 해석함에 있어서 균열선단 주위의 탄성 에너지 해방용, 균열확장력 그리고 응력장의 특성 등에 대한 지식을 요구하고 있다. 이런 연구들의 주안점은 에너지율, 응력장 그리고 탄성이방성체의 여러가지 경우들을 설명하는 데 있다. 철근콘크리트, 목재, 박층구조 그리고 각각의 방향으로 성질을 가지는 탄성체들은 대부분 직교이방성이다. 본 연구에서는 균열선단에 특이요소를 사용하고 균열선단 부근에서 아주 세밀한 요소를 사용하여 직교이방성 탄성체의 응력확대계수를 결정 하였다. 본 연구에서 응력확대계수를 구하기 위해 변위상관법을 사용하였으며 타 논문의 결과와 잘 일치함을 알 수 있었다.

• Geomechanics and Engineering
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• 제36권2호
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• pp.183-204
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• 2024

In current investigation, a novel beam finite element model is formulated to analyze the buckling and free vibration responses of functionally graded porous beams resting on Winkler-Pasternak elastic foundations. The novelty lies in the formulation of a simplified finite element model with only three degrees of freedom per node, integrating both C⁰ and C¹ continuity requirements according to Lagrange and Hermite interpolations, respectively, in isoparametric coordinate while emphasizing the impact of z-coordinate-dependent porosity on vibration and buckling responses. The proposed model has been validated and demonstrating high accuracy when compared to previously published solutions. A detailed parametric examination is performed, highlighting the influence of porosity distribution, foundation parameters, slenderness ratio, and boundary conditions. Unlike existing numerical techniques, the proposed element achieves a high rate of convergence with reduced computational complexity. Additionally, the model's adaptability to various mechanical problems and structural geometries is showcased through the numerical evaluation of elastic foundations, with results in strong agreement with the theoretical formulation. In light of the findings, porosity significantly affects the mechanical integrity of FGP beams on elastic foundations, with the advanced beam element offering a stable, efficient model for future research and this in-depth investigation enriches porous structure simulations in a field with limited current research, necessitating additional exploration and investigation.