• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 추계학술대회 논문집
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• pp.305-312
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• 1998

A formulation to perform static equilibrium and linear vibration analysis is presented in this paper. The formulation employs minimum number of equations of motion which are derived by using a partial velocity matrix, The static equilibrium analysis is performed first, then the linear vibration analysis is performed at the static equilibrium position. By using the formulation presented in this paper, static equilibrium and linear vibration analysis of a high speed electric train system are performed. A single bogie system, a power vehicle, and a train system which consists of five vehicles are analyzed, respectively. Natural frequencies and a few lowest mode shapes of the three are identified in this paper.

• 대한화학회지
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• 제47권6호
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• pp.578-584
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• 2003

토양오염표준공정시험법과 정적 초임계 $CO_2$ 추출방식을 사용하여 환경오염물질로 알려져 있는 토양 중의 PCBs를 분석하였다. 토양오염표준공정시험법에 의한 PCBs의 평균회수율은 25-35%의 범위였으며 표준편차는 10%를 초과하였다. 이와는 대조적으로, 정적 초임계 $CO_2$ 추출방식에 의한 PCBs의 평균회수율은 토양오염표준공정시험법보다도 2-2.5배 높았으며 표준편차는 7% 이내였다. 이러한 결과들은 정적 초임계 $CO_2$ 추출방식이 토양오염표준공정시험법에서 공인된 시료전처리과정을 대체할 수 있을 가능성을 제시하고 있다. $40^{\circ}C$의 일정한 온도에서 점차적으로 초임계 $CO_2$의 압력을 1130 psi에서 1196 psi로 증가시킴에 따라 토양으로부터 PCB congener의 회수율도 역시 증가하는 경향을 보였으나, 같은 추출조건(같은 온도와 압력)에서 평형시간(5분과 60분)은 회수율의 어떠한 영향도 주지 않았다. 마지막으로, 각 PCB congener의 회수율은 같은 추출조건에서 PCB의 분자량이나 구조(coplanar versus non-coplanar)와는 관계없이 거의 비슷한 수준의 값을 보였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1289-1294
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• 2008

Electrostatic discharge(ESD) phenomenon is a serious reliability concern. It causes approximately most of all field failures of IC. To quality the ESD immunity of IC product, there are some test methods and standards developed. ESD events have been classified into 3 models, which are HBM, MM and CDM. All the test methods are designed to evaluate the ESD immunity of IC products. This study provides an overview among ESD test methods on ICs and an efficient ESD stress method. We have estimated on all pin combination about the positive and negative ESD stress. We make out the weakest stress mode. This mode called a worst-case mode. We proposed that positive supply voltage pin and I/O pin combination is efficient because it is a worst-case mode.

• 한국구조물진단유지관리공학회 논문집
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• 제21권3호
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• pp.60-68
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• 2017

교량은 사회간접시설물의 핵심이 되는 도로의 주요 시설물이므로 공용기간 동안 안정성과 사용성이 확보될 수 있도록 건설되며, 교량의 안전성 확보를 위하여 현재 상태에서 건전성을 평가하는 것은 유지관리 업무에서 중요한 과제이다. 일반적으로 교량의 내하력 평가를 위해 차량재하시험을 통하여 횡분배율을 측정함으로써 교량의 중첩거동 및 대칭거동을 확인할 수 있다. 그러나 공용중인 교량의 횡분배율을 측정하기 위하여 정적재하시험을 수행하고 있으며 교통통제의 어려움이 있다. 따라서 본 연구에서는 동적재하시험 및 상시진동시험에서 측정된 교량의 변위응답 데이터를 경험적 모드분해기법을 이용하여 정적 성분의 변위를 추출하였다. 추출된 정적 성분의 변위를 이용하여 횡분배율을 추정하였으며, 정적재하시험에서 측정된 횡분배율과 비교하였다.

• 한국산학기술학회논문지
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• 제9권6호
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• pp.1500-1505
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• 2008

본 논문은 원자력 내진등급 IIA 글로브 밸브의 지진하중에 대한 구조 건전성을 평가하였다. 밸브 구조물을 3차원 모델링하여 유한요소법을 사용하여 모달 해석 및 등가 정적 응력해석을 수행하였다. 모달 해석 결과 밸브 구조물은 충분히 강건하여 등가 정적해석이 가능하였고 해석에서 구한 응력들을 조합하여 원자력 규격집에서 제시한 허용응력과 비교하여 밸브의 구조 건전성을 판단하였다. 모든 지진하중에 대한 밸의 구조물에서의 응력은 허용값 보다 작게 분포하므로 구조적 건전성을 유지한다고 평가할 수 있다.

• Structural Engineering and Mechanics
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• 제35권4호
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• pp.387-407
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• 2010

In this paper, using perturbation and Galerkin method, the response of a resonant viscoelastic microbeam to an electric actuation is obtained. The microbeam is under axial load and electrical load. It is assumed that midplane is stretched, when the beam is deflected. The equation of motion is derived using the Newton's second law. The viscoelastic model is taken to be the Kelvin-Voigt model. In the first section, the static deflection is obtained using the Galerkin method. Exact linear symmetric mode shape of a straight beam and its deflection function under constant transverse load are used as admissible functions. So, an analytical expression that describes the static deflection at all points is obtained. Comparing the result with previous research show that using deflection function as admissible function decreases the computation errors and previous calculations volume. In the second section, the response of a microbeam resonator system under primary and secondary resonance excitation has been obtained by analytical multiple scale perturbation method combined with the Galerkin method. It is shown, that a small amount of viscoelastic damping has an important effect and causes to decrease the maximum amplitude of response, and to shift the resonance frequency. Also, it shown, that an increase of the DC voltage, ratio of the air gap to the microbeam thickness, tensile axial load, would increase the effect of viscoelastic damping, and an increase of the compressive axial load would decrease the effect of viscoelastic damping.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.97-104
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• 1999

Brake squeal noise has been a problem since the early days of motoring . It is important to obtain vibration mode shape for reduction of brake noise . Stroboscopic Electronic Speckle Pattern Interferometry is a very powerful measuring method for study of vibrating objects in static state compared with conventional methods because this method can give both resonance frequency and quantitative visualization of vibration mode shape at the same time. In this paper, we performed qualitative visualization and quantitative analysis of vibration mode shpae of disk brake by using stroboscopic ESPI and phase shifting method. The stroboscopic wavefronts are obtained by chopping continuous wave laser beam using acousto-optic modulator .Experiments were performed at the same constraint conditions as disk brake of the practical vehicle as far as possible. The experimental results of this paper show quantitative measurement of vibration mode shape and quantiative visualization of vibration amplitude of disk brake with 3D plotting.

• 대한기계학회논문집A
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• 제23권6호
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• pp.1039-1047
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• 1999

It is necessary to evaluate the fatigue behavior of rail steel under the multi-axial stress state to assure the railway vehicle's safety. For this purpose, the stress analysis to investigate the crack initiation criteria, static failure and fatigue behavior under mixed-mode are performed. The stress analysis results show that the initiation of the transverse fissure depends on the maximum shear stress below the surface. For the mixed mode, the fatigue crack growth behavior which is represented by the projection crack length and comparative S.I.F, ${\Delta}K_v$, shows the more conservative results. Also, its rate is lower than that of the case of the mode I, and this difference decreases with increasing the stress ratio, R.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.874-880
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• 2003

Many mechanical systems are over-constrained if only rigid bodies are used to model the system. One example of such system is a satellite system with solar panels. To avoid this over-constrained problem, solar panels can be modeled as flexible bodies. The CMS(Component Mode Synthesis) method is widely used to analyze the flexible multi-body system because it can considerably approximate the deformation of the flexible bodies using small number of well-selected mode. However, it is very difficult to decide the boundary condition and the selection of modes. In this paper, the methods for mode synthesis and setting the boundary condition are presented to analyze the flexible multi-body system with over-constraints. Finally, the reliability of proposed method is verified by solar panel's deployment test.

• 한국정밀공학회지
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• 제18권2호
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• pp.63-71
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• 2001

This paper introduces a method for calculation of dynamic stress occurring in flexible bodies of a moving multibody system by using commercial softwares DADS for dynamic analysis and MSC/NASTRAN for finite element analysis. Three methods for model transient response analysis of a flexible body are summarized. Elastic deformation of a flexible body can be described with normal modes and static modes composed of constraint modes and residual attachment modes. The deformation modes divided into fixed-interface modes and free-interface modes can be determined by using MSC/NASTRAN and selected for dynamic analysis. The dynamic results obtained from DADS are utilized to calculate dynamic stress by using mode-displacement method or mode-acceleration method of MSC/NASTRAN. As a numerical example of the analysis, we used a three dimensional slider-crank model with a flexible connecting rod.