• 한국소음진동공학회논문집
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• 제20권5호
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• pp.477-485
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• 2010

In this study, we suggested several approaches to evaluate the collision acceleration of a carbody under the article 16 of the Korean rolling stock safety regulations. There are various methods to evaluate the rigid body accelerations such as the displacement comparison method by double integration of filtered acceleration data, the velocity comparison method by direct integration of filtered acceleration data, and the analysis method of a velocity-time curve. We compared these methods one another using the 1D dynamic simulation model of Korean high-speed EMU composed of nonlinear springs or bars, dampers, and masses. From the simulation results, the velocity-time curve analysis method and the displacement comparison method are recommended to filter high frequency oscillations and evaluate the maximum and average accelerations of a carbody after a train collision.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.107-110
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• 1999

The purpose of this research is for the development of a new type forging equipment H.C.G(Hyundai Continuous Grain-flow) by using two virtual build-up tools rigid viscoplastic FEM and downsized plasticine experiment. This forging equipment consists of consecutive horizontal and vertical pressure while the traditional forging method consists of only vertical pressure. Using this method high quality crankshafts can be forged as it can maintain a continuous grain flow. The factors considered in the development of equipment are die geometry for flawless deformed shape die reaction forces stress/strain distributions and continuous material flow. We carried out several numerical simulations and downsized plasticine experiments for the proper design of the forging equipment. The validity of those simulation results is confirmed by checking with the actual test results. Based on these simulation results the proper design of the H.C.G for ging equipment is enabled.

• 한국멀티미디어학회논문지
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• 제21권7호
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• pp.787-794
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• 2018

We propose a new framework which expresses the mist and scratches of cracked ice by an impact. We combine the grid projection technique, boundary particles method, and level-set method commonly used in fluid simulations to determine the region on the surface of an ice object which is affected by a collision. Mist is then generated in proportion to the impact, and immediately diffused, using a geodesic distance field to limit dissipation. The gradient of the mist is subsequently used to create realistic patterns of scratches and elongated air bubbles. Cracks of the ice object can also be considered, and the density of the mist made to vary realistically between fragments. As a result, our method not only represents high-quality ice effects, but also allows easy integration into existing rigid body simulation solvers.

• Bulletin of the Korean Chemical Society
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• 제23권3호
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• pp.441-446
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• 2002

We have presented the results of thermodynamic, structural and dynamic properties of liquid benzene, toluene, and p-xylene in canonical (NVT) ensemble at 293.15 K by molecular dynamics (MD) simulations. The molecular model adopted for these molecules is a combination of the rigid body treatment for the benzene ring and an atomistically detailed model for the methyl hydrogen atoms. The calculated pressures are too low in the NVT ensemble MD simulations. The various thermodynamic properties reflect that the intermolecular interactions become stronger as the number of methyl group attached into the benzene ring increases. The pronounced nearest neighbor peak in the center of mass g(r) of liquid benzene at 293.15 K, provides the interpretation that nearest neighbors tend to be perpendicular. Two self-diffusion coefficients of liquid benzene at 293.15 K calculated from MSD and VAC function are in excellent agreement with the experimental measures. The self-diffusion coefficients of liquid toluene also agree well with the experimental ones for toluene in benzene and for toluene in cyclohexane.

• 한국정밀공학회지
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• 제16권4호통권97호
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• pp.95-101
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• 1999

In this paper, we propose a dynamic model of an escalator which can be used to build a design database. The model permits to estimate the forces applied to the structure by calculating three primary types of forces; the torque required to operate the escalator, the reaction forces at part interconnection points, and contact forces between parts. These forces can then be used to calculate dynamic stresses in the structure which is required to estimate the durability of the structure. Result of the computer model are compared with testing results. This simulation model is used to construct a design database. So when we design a new escalator, this design database can be used to make a new simulation model which makes it possible for us to do a Knowledge-Based-Design.

• 소성∙가공
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• 제8권3호
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• pp.237-244
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• 1999

The purpose of this research is for the development of a new type forging equipment. H.C.G.(Hyundai Continuous Grain-Flow), by using two virtual build-up tools, rigid viscoplastic FEM and downsized plasticine experiment. This forging method consists of only vertical pressuree. Therefore, high quality crankshafts can be forged with this method as it can maintain a continuous grain flow. The factors considered in the development of equipment are die geometry for flawless deformed shape, die reaction forces, stress/strain distributions and continuous material flow. We carried out several numerical simulations and downsized plasticine experiments for the proper design of the forging equipment. The validity of those simulation results is confirmed by checking with the actual test results. Based on these simulation results, the proper design of the H.C.G. forging equipment is enabled.

• 대한기계학회논문집A
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• 제29권2호
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• pp.270-276
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• 2005

This paper develops the flexible computational model of a heavy truck by interfacing the frame modeled as a flexible body to the heavy truck's computational model composed of rigid bodies. The frame is modeled by the finite element method. Three torsional modes and three bending modes of the frame are considered for the interface of the heavy truck's computational model. The actual vehicle test is conducted off road with a velocity of 20km/h. The vertical accelerations at the cab and front axle are measured in the test. For the verification of the developed computational model, the measured vertical acceleration profiles are compared with the simulation results of the heavy truck's flexible computational model. E grade irregular road profile of ISO is used as an excitation input in the simulation. The verified flexible computational model is used to compare the vibration characteristics of a front suspension system having a multi-leaf spring and that having a tapered leaf spring. The comparison results show that the front suspension having a tapered leaf spring has a higher vertical acceleration at the front axle but a lower vertical acceleration at the cab than the suspension system having a multi-leaf spring.

• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1638-1645
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• 2006

This paper proposes a modeling technique which is able to not only reliably and easily represent the hysteretic characteristics but also analyze the dynamic stress of a taper leaf spring. The flexible multi-body dynamic model of the taper leaf spring is developed by interfacing the finite element model and computation model of the taper leaf spring. Rigid dummy parts are attached at the places where a finite element leaf model is in contact with an adjacent one in order to apply contact model. Friction is defined in the contact model to represent the hysteretic phenomenon of the taper leaf spring. The test of the taper leaf spring is conducted for the validation of the reliability of the flexible multi-body dynamic model of the taper leaf spring developed in this paper. The test is started at an unloaded state with the excitation amplitude of $1{\sim}2mm/sec$ and frequency of 132 mm. First, the simulation is conducted with the same condition as the test. Then, the simulations are conducted with various amplitudes in a loaded state. The hysteretic diagram from the test is compared with the ones from the simulation for the validation of the reliability of the model. The dynamic stress analysis of the taper leaf spring is also conducted with the developed flexible multi-body dynamic model under a dynamic loading condition.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.83-86
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• 2007

Turbulent flow analysis is conducted around the multi-stage launch vehicle including base region and detachment motion of strap-on boosters due to resultant aerodynamic forces and gravity is simulated. Aerodynamic solution procedure is coupled with rigid body dynamics for the prediction of separation behavior. An overset mesh technique is adopted to achieve maximum efficiency in simulating relative motion of bodies and various turbulence models are implemented on the flow solver to predict the aerodynamic forces accurately. At first, some preliminary studies are conducted to show the importance of base flow for the exact prediction of detachment motion and to find the most suitable turbulence model for the simulation of launch vehicle configurations. And then, developed solver is applied to the simulation of KSR-III, a three-stage sounding rocket researched in Korea. From the analyses, after-body flow field strongly affects the separation motions of strap-on boosters. Negative pitching moment at initial stage is gradually recovered and a strap-on finally results in a safe separation, while fore-body analysis shows collision phenomena between core rocket and booster. And a slight variation of motion is observed from the comparison between inviscid and turbulent analyses. Change of separation trajectory based on viscous effects is just a few percent and therefore, inviscid analysis is sufficient for the simulation of separation motion if the study is focused only on the movement of strap-ons.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2009년도 학술대회
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• pp.463-468
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• 2009

본 논문은 데스크탑 PC 에서만 구현 가능하였던 기존의 유체 시뮬레이션 기술을 모바일 환경으로 확장하는 방법론을 제시한다. 유체 시뮬레이션은 나비어-스토크스 (Navier-Stokes) 방정식의 수치적 해를 구하는 것이며, 기존의 방법론은 수치적 해의 안정성과 [1] 사실성 [2]에 그 초점을 맞추고 있다. 하지만 이는 모바일 기기에서 기대하기 힘든 충분한 연산 자원을 가정한 것이다. 한편, 모바일 환경에서의 물리기반 기술은 현재 강체 시뮬레이션 모듈이 주로 활용되고 있으며 [3], 유체 시뮬레이션은 높이장 (Height field) 기반의 단순한 모델만이 제시되어있다 [4]. 이를 극복하기 위해 본 연구에서는 이러한 한계를 극복한 수정된 비압축유동의 시뮬레이션 기법을 소개하며, 또한 모바일 상에서 유체의 가시화 기술을 제안한다.