• 소성∙가공
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• 제10권2호
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• pp.137-143
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• 2001

The change of flow stress due to dynamic recrystallization during hot forming process is investigated. A series of mechanical tests has been conducted at various temperatures, and constitutive relations and recrystallization kinetics were formulated from the test results. The effect of dynamic recrystallization to the flow stress was implemented to a commercial FEM code by conditioned remapping of state variables. The datum strain of stress compensation was optimized to minimize the overestimation of forming loads. Suggested datum was formulated as an exclusive function of critical strain for recrystallizalion and validated by mechanical tests and microstructural observations.

• 한국자동차공학회논문집
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• 제6권6호
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• pp.24-30
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• 1998

A directly coupled Boundary Element and Finite Element Model was applied to the dynamic analysis of a coupled acoustic silencer with vibratory wall. In this cupled BEM-FEM muffler model, the BEM model was used to discretize the acoustic cavity and the FEM model was used to discretize the vibratory wall structure. Then the BEM model was coupled with the FEM model. The results of the coupled BEM-FEM model for the dynamic analysis of the simple expansion type reactive muffler configurations with flexible walls were verified by comparing the predicted results to analytical solutions. In order to investigate the effects of the muffler's structural flexibility on its transmission loss(TL) characteristics, the results of the coupled BEM-FEM model in conjunction with the four-pole parameter theory were utilized. The muffler's TL characteristics using the BEM-FEM coupled model with flexible walls as compared to other muffler configurations was studied. Finally the muffler's TL values with respect to different wall's thickness are predicted and compared.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.131.1-134
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• 1999

The effect of dynamic recrystallization during hot forming process was implemented to a commercial FEM code by conditioned remeshing and remapping of sate variables. A datum strain for stress compensation was determined as a strain for maximum softening rate and was able to be formulated as a function of critical strain f($\varepsilon$). The validity of remapping criterion was examined by a series of mechanical tests and microstructural observation. The application of suggested datum resulted in better estimation of load-stroke during forging processes.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.238-243
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• 2002

This paper presents a design and a control of a biped walking AGO-robot and dynamic walking simulation for this system. The biped walking RGO-robot is distinguished from other one by which has a very light-weight and a new RGO type with servo motors. The gait of a biped walking AGO-robot depends on the constrains of mechanical kinematics and initial posture. The stability of dynamic walking is investigated by ZMP(Zero Moment Point) of the biped walking AGO-robot. It is designed according to a human wear type and is able to accomodate itself to human environments. The joints of each leg are adopted with a good kinematic characteristics. To test of the analysis of joint kinematic properties, we did the strain stress analysis of dynamic PLS and the study of FEM with a dynamic PLS. It will be expect that the spinal cord injury patients are able to train effectively with a biped walking RGO-robot.

• Journal of Electrical Engineering and Technology
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• 제2권3호
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• pp.346-352
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• 2007

In this paper, we present an analysis of dynamic characteristics of an electromagnetic actuator for circuit breakers. It is indispensable to simultaneously analyze magnetic, electric, and mechanical phenomena to obtain the dynamic characteristics of the electromagnetic actuator because these phenomena are closely related to each other in an electromagnetic actuator system. The magnetic equations are computed by using the finite element method (FEM). The electric equations and the mechanical equations, which include the time derivative terms, are calculated by using the time difference method (TDM). The calculated results, which have been obtained by means of the FEM and the TDM, are presented with experimental data.

• KSTLE International Journal
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• 제5권2호
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• pp.44-48
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• 2004

A new type slider with optical components is going to be introduced on market for portalbe and high capacity disk drive, and it will show a great potential for high performance drive in the paper the dynamic behavior and static characteristics of silder for a small form factor optical disk drive have been investigated numerically by an in-house simulation code using FEM. A curvature effect is found when a slider is applied to a relatively small disk, which makes rolling characteristics worse due to the negative pressured generated at the air bearing surface because of the curvature of small disk diameter.

• 한국터널지하공간학회 논문집
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• 제3권4호
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• pp.3-15
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• 2001

일반적으로 지진발생시 터널구조물은 지상구조물에 비해 입는 피해가 매우 작다고 해서 내진설계에 대한 인식이 부족하였다. 그러나, 현재까지 많은 유형의 지하터널이 건설되었고, 앞으로는 더 많은 건설계획이 있으므로 지진시 지하터널구조물에 대한 안정성 확보가 중요하고 많은 연구가 필요하다. 본 논문에서는 지진발생시 터널의 동적거동을 파악하고, 적절한 내진해석을 제안하기 위해서 응답변위법과 동적해석법을 이용하여 내진해석을 실시하였다. 해석 결과는 지진발생시 터널구조물이 지반의 변형에 순응한다는 것을 나타내었고, 응답변위법에 의한 내진해석이 동적해석법에 의한 것보다 대부분의 경우 더 보수적인 해석이라는 것을 보여주었으며, 마지막으로 동적해석시 간편화된 2차원유한요소해석이 복잡한 3차원해석보다 내진해석시 더 효율적이라는 것을 보여주었다. 갱구부의 내진해석결과에서는 지진파가 터널축과 평행하게 진행할 때 갱구부에 설치된 라이닝에 가장 큰 단면력이 발생하는 것으로 나타났다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.136-141
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• 2002

This paper presents a design and a control of a biped walking RGO-robot and dynamic walking simulation for this system. The biped walking RGO-robot is distinguished from other one by which has a very light-weight and a new AGO type with servo motors. The gait of a biped walking RGO-robot depends on the constrains of mechanical kinematics and initial posture. The stability of dynamic walking is investigated by ZMP(Zero Moment Point) of the biped walking RGO-robot. It is designed according to a human wear type and is able to accomodate itself to human environments. The joints of each leg are adopted with a good kinematic characteristics. To test of the analysis of joint kinematic properties, we did the strain stress analysis of dynamic PLS and the study of FEM with a dynamic PLS. It will be expect that the spinal cord injury patients are able to train effectively with a biped walking AGO-robot.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 추계학술대회 논문집
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• pp.55-61
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• 2000

Tungsten heavy metal is characterized bi a high density and novel combination of strength and ductility. Among them, 90W-7Ni-3Fe is used for applications, where the high specific weight of the material plays an important role. They are used as counterweights, rotating inertia members, as well as for defense purposes(kinetic energy penetrators, etc.). Because of these applications, it is essential to detemine the dynamic characteristics of tungsten alloy. In this paper, Explicit FEM(finite element method) is employed to investigate the dynamic characteristics of tungsten heavy metal under base of stress wave propagation theory for SHPB, and the model of specimen is divided into two parts to understand the phenomenon that stress wave penetrates through each tungsten base and matrix. This simulation results were compared to experimental one and through this program the dynamic stress-strain curve of tungsten heavy metal can be obtained using quasi static stress-strain curve of pure tungsten and matrix.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.752-759
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• 2002

This paper presented a design and a control of a biped walking RGO and walking simulation by this system. The biped walking RGO was distinguished from the other one by which had a very light-weight and a new RGO type with 12-servo motors. The vibration evaluation of the dynamic PLS on the biped walking RGO was used to access by the 3-axis accelerometer with a low frequency vibration for the spinal cord injuries. The gait of a biped walking RGO depended on the constrains of mechanical kinematics and the initial posture. The stability of dynamic walking was investigated by a ZMP (Zero Moment Point) of the biped walking RGO. It was designed according to a human wear type and was able to accomodate itself to a human environments. The joints of each leg were adopted with a good kinematic characteristics. To test of the analysis of joint kinematic properties, we did the strain stress analysis of the dynamic PLS and the analysis study of FEM with a dynamic PLS. It will be expect that the spinal cord injury patients are able to recover effectively with a biped walking RGO.