• Proceeding of KASS Symposium
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• 2008.05a
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• pp.74-79
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• 2008

In this study, impact transient responses of (Graphite/Epoxy) laminated composite subjected to low-velocity impact are investigated using a finite element method. Dynamic von-Karman plate equations considering large deflection of plate are modified to include the effect of transverse shear deformations as in Mindlin plate theory and also the rotary inertia effect is considered. The convergence of transient responses is used contact law established through the statical indentation test. We investigate displacements, contact forces and strains by thickness variation of various laminated composite. We compare and analyze each results.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.681-684
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• 2008

In case of recycled fine aggregate, density and absorption ratio is lower than natural one, so it is used to lower value added products and it is limited its usage. It is reported that Compressive and tensile strength of recycled concrete is more deteriorate and shrinkage properties is very deteriorate because high absorption of recycled fine aggregate. Accordingly, in this study, it is develop that dry manufacturing system composed specific gravity separator of high-speed rotation impact type, reclaimer of minuteness fine aggregate and evaluate that shrinkage properties of recycled concrete using recycled fine aggregate at producing this system. Hereafter, it is present that fundamental data to practical use recycled fine aggregate.

• Journal of Ocean Engineering and Technology
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• v.28 no.2
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• pp.111-118
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• 2014

In drilling process of oil wells, the drilling fluid such as mud keeps the drill bit cool and clean during drilling, with suspending drill cuttings and lubricating a drill bit. In this paper, a commercial CFD package(ANSYS Fluent 15.0) was used to solve the hydrodynamic force and evaluate mud mixing time in the mud mixing tank on offshore drilling platforms. Prediction of power consumption in co-rotating and counter-rotating models has been compared with results of Nagata's correlation equation. This research shows the hydrodynamic effect inside the two phase mud mixing tank according to rotating directions(co-rotating and counter-rotating). These results, we can conclude that the co-rotating direction of the two shafts with mixing blade in the mud mixing tank can be a preferable in power consumption and mixing time reduction.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.585-590
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• 2000

The hydrodynamic instability of the three-dimensional boundary layer on a rotating disk introduces a periodic modulation of the mean flow in the form of stationary cross flow vortices. Detailed numerical values of the growth rates, neutral curves and other characteristics of the two instabilities have been calculated over a wide range of parameters. Presented are the neutral stability results concerning the two instability modes by solving new linear stability equations reformulated not only by considering whole convective terms but by correcting some errors in the previous stability equations. The present stability results are agree with the previously known ones within reasonable limit. The flow is found to be always stable for a disturbance whose dimensionless wave number at Re=1200 is greater than 0.75. Also, the spatial amplification contours have been calculated for the moving disturbance wave, whose azimuth angle is between ${\varepsilon}=15^{\circ}$ and $12.5^{\circ}$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.2090-2097
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• 1992

In this paper, fluttering behavior of mechanical monloleaflet heart valve prosthesis was analyzed taking into consideration of the impact between the valve occluder and the stopper. The motion of valve occluder was modeled as a rotating system, and equations were derived by employing the moment equilibrium conditions. Lift force, drag force, gravity and buoyancy were considered as external forces acting on the valve occluder. The 4th order Runge-Kutta method was used to solve the equations. The results demonstrated that the occluder reaches steady eguilibrium position only after damped vibration. The mean damping ratio is in the range of 0.197-0.301. Fluttering frequency does not have any specific value, but varies as a function of time. It is in the range of 11-84Hz. Valve opening appears to be affected by the orientation of the valve relative to gravitational forces.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.1
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• pp.76-81
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• 2016

At negative-g condition, a float-type valve can open the passage of fuel in order to it flows continuously through a pressurized fuel tank system. Since specialized test conditions and high-cost supports are required, it is truly difficult to test the valve in a real high-speed test. Therefore, this paper contains performance analysis of a float-type fuel supply valve through flight tests conducting roll and negative-g maneuvers.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.4
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• pp.149-155
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• 2016

This paper presents a control method of a mecanum wheel-based omni-directional electric board using driver weight shift. Instead of a steering device such as a joystick or a remote controller, 3 degree-of-freedom driving command for translational and rotational motion of the omni-directional electric board is generated from position of center of gravity measured from weight distribution. The weight shifting motion is not only a driving command but also an intuitive motion to overcome inertial forces. The overall control structure is presented with experimental results to prove validity of the proposed method.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.1
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• pp.43-55
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• 2001

본 논문에서는 현행 표준적인 P.S.C거더 교량의 적정 가로보 수를 위한 매개변수 연구를 수행하였다. 교량의 길이는 P.S.C거더교로서 국내에서 가장 흔히 사용되는 30m의 단순교를 채택하였다. 교량의 해석방법으로는 상부의 슬래브와 거더를 효율적으로 모델링하기 위하여 정밀해석법인 유한요소법을 사용하였다. 본 연구에서 사용된 매개변수로는 크게 두 가지로 분류되는데, 하나는 사용된 가로보의 개수이고 다른 하나는 교량의 사각(Skew)이다. 상부 슬래브는 쉘 요소와 빔 요소를 연결하는데 효율적인 회전자유도를 가지는 쉘 요소로 모델링 하였다. 슬래브와 거더의 중심축이 이격되어 있는 문제를 정확히 고려하기 위하여 편심보 요소를 사용하였다. 해석 모델은 가로보가 각각 7,5,3개 있는 경우를 선정하였다. 이러한 조건하에서 정적 해석을 수행하여 최대 휨모멘트, 전단력, 비틀림 모멘트값을 구하여 현행 시방서에서 규정된 극한치를 만족하는지 검토하였다. 검토결과 현재 사용되고 있는 P.S.C거더 교량에서의 가로보 개수는 과다한 것으로 판단되며 경제적인 설계를 위하여 가로보의 개수를 줄일 수 있을 것으로 제안하였다.

• Tunnel and Underground Space
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• v.21 no.3
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• pp.174-180
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• 2011

An anisotropic version of Mohr-Coulomb failure criterion is proposed in order to provide a strength criterion for transversely isotropic rock. The concept of fabric tensor introduced by Pietruszczak & Mroz (2001) is employed to define the friction angle and cohesion as scalar functions of the fabric tensors. The anisotroy in these two strength parameters are calculated in association with the consideration of the relative rotation between the principal stress coordinate and the principal material triad. The critical plane on which the anisotropic function maximized is found by an optimization technique based on the Lagrange multiplier method. To demonstrate the performance of the anisotropic failure criterion, conventional triaxial tests on the samples having various inclinations of weakness plane are simulated and the resulting triaxial strength and dip angle of failure plane are discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1992.10a
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• pp.98-103
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• 1992

전세계적인 에너지 절약과 환경보존에 대한 관심과 요구가 증가함에 따라 소비전력규제와 CFC삭감에 대응한 국제경쟁력 확보가 중요한 과제로 대두 되고 있다. 이러한 상황변화에 따라 냉동 공조기기의 심장부인 압축기에 대 해서도 고효율 및 저소음화의 요구가 한층 높아졌다. 따라서 가혹한 환경에 도 견딜 수 있는 압축기의 개발은 필수적이라 할 수 있다. 소형밀폐형 압축 기는 크게 두 부분으로 나뉘어진다. 그 하나는 모터에 의한 회전구동부이고, 다른 하나는 실린더와 피스톤 그리고 밸브로 구성된 압축기구부이다. 그 중 에서 밸브는 진동 및 소음에 영향을 미치는 기본요소가 된다. 압축기의 밸브 는 근본적으로 밸브포트와 실린더 형상에 의해 결정되며, 이런 형상조건하에 서 밸브는 연속적인 운전이 되어야 하므로, 그 응답성이 좋아야 하고 무엇보 다도 자체의 신뢰성도 확보되어야 한다. 따라서 밸브의 동적특성과 응력 분 포를 정확히 예측하는 것이 중요한 과제가 된다. 본 논문에서는 컴퓨터를 이 용한 밸브의 동적특성과 응력해석을 위해 밸브의 형상을 유한요소 패키지인 ANSYS를 이용하여 해석하고, 그 모델링 및 해석이 타당성을 검토하기 위하 여 동적 특성해석은 홀로그래피(Holography) 기술을 이용하여 실험하고, 응 력해석은 스트레인 게이지(strain gage)를 이용하여 결과를 얻어서 서로 비 교하여 보았다.