• 대한기계학회논문집B
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• 제37권2호
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• pp.111-117
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• 2013

탄성튜브가 연결된 펌핑 챔버를 이용한 무밸브 펌프를 가상경계방법을 이용하여 수치적으로 연구하였다. 탄성 튜브와 펌핑 챔버 사이의 상호작용으로 인하여 무밸브 펌프 내의 유동이 생성되었으며, 탄성튜브의 스트레칭 계수, 벤딩 계수, 종횡비가 무밸브 펌프의 전체 유량에 미치는 영향을 살펴보았다. 펌프의 메커니즘을 이해하고자, 시간에 따른 탄성 튜브의 움직임과 그에 따른 유동 속도의 변화를 자세히 살펴보았으며, 탄성 튜브의 직경 크기와 펌프의 평균 유량 사이의 관계를 분석하였다.

• Advances in materials Research
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• 제5권1호
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• pp.35-53
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• 2016

Flexural bending analysis of perfect and imperfect functionally graded materials plates under hygro-thermo-mechanical loading are investigated in this present paper. Due to technical problems during FGM fabrication, porosities and micro-voids can be created inside FGM samples which may lead to the reduction in density and strength of materials. In this investigation, the FGM plates are assumed to have even and uneven distributions of porosities over the plate cross-section. The modified rule of mixture is used to approximate material properties of the FGM plates including the porosity volume fraction. In order the elastic coefficients, thermal coefficient and moisture expansion coefficient of the plate are assumed to be graded in the thickness direction. The elastic foundation is modeled as two-parameter Pasternak foundation. The equilibrium equations are given and a number of examples are solved to illustrate bending response of Metal-Ceramic plates subjected to hygro-thermo-mechanical effects and resting on elastic foundations. The influences played by many parameters are investigated.

• Journal of Mechanical Science and Technology
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• 제18권9호
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• pp.1500-1511
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• 2004

In this paper, the anti-plane transient response of a central crack normal to the interface between a piezoelectric ceramics and two same elastic materials is considered. The assumed crack surfaces are permeable. By virtue of integral transform methods, the electro elastic mixed boundary problems are formulated as two set of dual integral equations, which, in turn, are reduced to a Fredholm integral equation of the second kind in the Laplace transform domain. Time domain solutions are obtained by inverting Laplace domain solutions using a numerical scheme. Numerical values on the quasi-static stress intensity factor and the dynamic energy release rate are presented to show the dependences upon the geometry, material combination, electromechanical coupling coefficient and electric field.

• Steel and Composite Structures
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• 제44권1호
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• pp.17-31
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• 2022

This investigation studies the characteristics of wave dispersion in sigmoid functionally graded (SFG) curved beams lying on an elastic substrate for the first time. Homogenization process was performed with the help of sigmoid function and two power laws. Moreover, various materials such as Zirconia, Alumina, Monel and Nickel steel were explored as curved beams materials. In addition, curved beams were rested on an elastic substrate which was modelled based on Winkler-Pasternak foundation. The SFG curved beams' governing equations were derived according to Euler-Bernoulli curved beam theory which is known as classic beam theory and Hamilton's principle. The resulted governing equations were solved via an analytical method. In order to validate the utilized method, the obtained outcomes were compared with other researches. Finally, the influences of various parameters, including wave number, opening angle, gradient index, Winkler coefficient and Pasternak coefficient were evaluated and indicated in the form of diagrams.

• Tribology and Lubricants
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• 제19권4호
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• pp.230-236
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• 2003

In applications such as MEMS and NEMS devices, the adhesion force and contact load may be of the same order of magnitude and the static friction coefficient can be very large. Such large coefficient may result in unacceptable and possibly catastrophic adhesion, stiction, friction and wear. To obtain the static friction coefficient of contacting real surfaces without the assumption of an empirical coefficient value, numerical simulations of the contact load, tangential force, and adhesion force are preformed. The surfaces in dry contact are statistically modeled by a collection of spherical asperities with Gaussian height distribution. The asperity micro-contact model utilized in calculation (the ZMC model), considers the transition from elastic deformation to fully plastic flow of the contacting asperity. The force approach of the modified DMT model using the Lennard-Jones attractive potential is applied to characterize the intermolecular forces. The effect of the surface topography on the static friction coefficient is investigated for cases rough, intermediate, smooth, and very smooth, respectively. Results of the static friction coefficient versus the external force are presented for a wide range of plasticity index and surface energy, respectively. Compared with those obtained by the GW and CEB models, the ZMC model is more complete in calculating the static friction coefficient of rough surfaces.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.941-944
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• 2006

Construction industry is one of the fastest growing sectors in the world. Rapid construction activity and growing demand of houses have led traditional building materials. In order to satisfy that purpose, the researchers need to vary new and innovative building materials. This paper describes the experiment carried out to investigate the elastic coefficient of loess due to compressive strength.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1996년도 창립기념 전력전자학술발표회 논문집
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• pp.47-51
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• 1996

In this paper, we propose a method for compliance control of a SCARA type 2-freedom direct drive(DD) manipulator. Each joint of the manipulator is driven by a travelling ultrasonic motor(USM). The travelling USM has good some characteristics over conventional servo motors such as compact size, light weight, silent motion, high torque and high speed response. By controlling the elasticity and viscosity of robot joints, a robot can work in compliance with external environment. we control the elastic coefficient and the viscous coefficient of joint by adjusting the phase difference of the motor power. And we contemplate transient response of USM with adjusting the elastic coefficient and the viscous coefficient. To use the result, we can control the robot to reach its goal with compliance motion. It remains for further research to develop the impedance control of USM.

• 대한전자공학회논문지
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• 제10권3호
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• pp.53-60
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• 1973

압전결정 LiMbO3와 LiTaO3의 로테이트 Y캇트, X전반의 탄성표면파(Rayleigh 표면파)의 위상속도 및 지연시간의 온도계수를 수치해석방법에 의해서 계산하였으며 LiNbO3 130°로테이트 Y캇트, 총전반의 탄성표면파의 온도계수를 액체 He의 온도로부터 실온까지 측정하였다. 이 지연시간의 온도계수의 실험치 70×10-6/℃는 계산치 72.7×10-6/℃와 잘 일치함을 확인하였다. 또한 LiNbO3 130° 로테이트 Y캇트, X전반의 탄성표면파의 지연시간의 온도계수는 액체 He온도근처에서 약 16×10-6/℃로 작아짐을 알았다.

• 지질공학
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• 제29권3호
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• pp.339-349
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• 2019

국내 40개 구조물 설계 시 수행된 1,646개의 실내 및 현장시험 결과를 활용하여 국내 암종에 따른 동탄성계수의 분포특성을 파악하기 위하여 암종별 P파 속도, 정탄성계수, 동탄성계수 간의 상관식을 도출하고 기존 연구사례와 비교하여 검증하였다. P파 속도와 정탄성계수의 관계를 살펴보면 편마암에서는 선형, 화강암과 사암에서는 지수 함수의 관계를 보인다. 결정계수($R^2$)는 0.491~0.642로 높지 않지만, 결정계수를 0.836~0.990로 제시하고 있는 기존의 연구사례와 유사한 분포범위를 보인다. 정탄성계수와 동탄성계수의 상관식은 모든 암종에서 선형적인 관계를 보이며, 결정계수는 0.543~0.676이다. P파 속도와 동탄성계수의 상관식은 지수함수의 관계를 보이며, 결정계수는 0.875~0.940으로 높게 나타난다.

• Advances in materials Research
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• 제9권1호
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• pp.33-48
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• 2020

With the use of differential quadrature method (DQM), forced vibrations and resonance frequency analysis of functionally graded (FG) nano-size beams rested on elastic substrate have been studied utilizing a shear deformation refined beam theory which contains shear deformations influence needless of any correction coefficient. The nano-size beam is exposed to uniformly-type dynamical loads having partial length. The two parameters elastic substrate is consist of linear springs as well as shear coefficient. Gradation of each material property for nano-size beam has been defined in the context of Mori-Tanaka scheme. Governing equations for embedded refined FG nano-size beams exposed to dynamical load have been achieved by utilizing Eringen's nonlocal differential law and Hamilton's rule. Derived equations have solved via DQM based on simply supported-simply supported edge condition. It will be shown that forced vibrations properties and resonance frequency of embedded FG nano-size beam are prominently affected by material gradation, nonlocal field, substrate coefficients and load factors.