• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(III)
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• pp.79-84
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• 2003

A fictitious crack model was used to analyze fatigue crack growth under the influence of residual stress. In the fictitious crack model, crack is represented in terms of the separation of two adjacent interfaces and the constitutive equation between the separation and traction is assumed. The effect of fatigue loading was included in the constitutive equation by considering damage accumulation in the cohesive zone. To investigate the effect of the residual stress on the fatigue crack growth, we calculated the residual stress distribution due to transient heat flux to the specimen by finite element method. Fatigue crack growth was simulated by the fictitious crack model with repeated loading. The mode-I crack growth rates were compared for the cases with and without the compressive residual stress around the crack tip. It was observed that the mode-I crack growth can be suppressed by compressive residual stress.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1183-1186
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• 2004

Degradation and insulation failure of traction motor depend on the continuous stress imposed on it. And knowing on insulation condition is important thing for safety operation of EMU(electric multiple unit). In this paper, PD(partial discharge) characteristics for degradation analysis of stator coil is studied. For PD data acquisition, two models are made; one is normal condition coil, the other is aged condition coil. And PD data for discrimination were acquired from PD detector. And these data making use of a computer-aided discharge analyser, statistical and other discharge parameters is calculated to discrimination between different discharge sources. And also these parameter is applied to classify PD sources by neural networks. Neural Networks has good recognition rate for degradation of stator coil.

• 대한기계학회논문집
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• 제8권3호
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• pp.232-240
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• 1984

본 논문에서는 Stern이 제시한 경로적분식을 기본방정식으로 하여 예리한 임 의 노치내각을 가진(크랙의 경우 0˚), 즉 r$^{.lambda.}$ 형태의 특이점을 포함한 모우드-I 및 II 응력확대계수를 위한 특성해 및 보조해를 규정하고 선택모형문제로 예리한 노치 내각을 달리한 대칭 하중의 인장문제와 끝단 전단력하중하의 일단 고정보의 비대칭문 제의 응력확대계수를 기존의 재래식 유한요소법과 결합하여 계산하였다. 또한 각각 의 경우 적분경로 및 요소분할을 달리하여 수치해의 안정성 및 경로 독립성을 검토하 였다.

• 한국가시화정보학회지
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• 제16권2호
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• pp.38-44
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• 2018

Cellular jamming phenomenon, defined as a kinetic arrest, is a commonly observed event in dense cell aggregates in epithelial tissues. Cells lose their motility when the density of the cell population becomes too high. Yet, not much is known about how the jamming occurs and how it influences individual cells in the population. In this study, we investigated the mechanisms during the formation of the jammed state by visualizing various dynamic components such as velocity, traction, and intercellular stress. The visualized properties exhibited interrelated features in similar time domains that can be categorized into specific stages, namely migrating, transitional and steady state. During the migrating stage, cells generated spatially correlated tractions and migrations at the collective migration step and lost these properties becoming a transitional stage. These stepwise analyses presented correlative components which are expected to adjust for explaining the detailed mechanisms of cellular jamming.

• 한국전산구조공학회논문집
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• 제21권4호
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• pp.375-382
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• 2008

본 연구는 2차원 및 3차원 동적 탄소성 응력 해석을 위한 특수 적분해 경계요소법의 공식 개발을 제시한다 정적 탄성에 대한 기본식이 일반해를 구하는데 이용되었으며, 전체형상함수 개념을 이용하여, 변위율과 traction rate의 특수 적분해를 구함으로써 지배 방정식의 가속도 부분을 근사화시켰다. 시간 적분을 위하여 Houbolt 시적분 방법을 이용하였으며, Newton-Raphson 알고리즘을 이용하여 수치 연산을 행하였다. 제시된 공식에 따른 예제 해석을 통하여 그 방법의 유효성과 정확성을 설명하였다.

• 한국정밀공학회지
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• 제16권10호
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• pp.152-163
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• 1999

The problem of eigenvalue and eigenvector for v-notched cracks in pseudo-isotropic and anisotropic dissimilar materials was obtained to discuss stress singularities from traction free boundary and perfect bonded interface conditions assuming like the form of complex stress function for v-notched cracks in an isotropic material. Eigenvalues were solved by a commercial numerical program, MATHEMATICA. The relation between wedged angle and material property for eigenvalue, ${\lambda}$ indicating stress singularities of v-notched cracks in pseudo-isotropic and anisotropic dissimilar materials was examined.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 제2회 학술대회 논문집 일렉트렛트 및 응용기술전문연구회
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• pp.73-76
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• 2000

Traction motors that is one of the rotating machines for urban transit EMU have been subjected to increased demand for higher operating temperature, more demanding duty cycles, higher starting current, frequent voltage transients and severe environmental exposure. With the advent of PWM drives using power IGBTs in addition to the thermal considerations, it is important to take into account the impact of the dielectric stress upon the winding insulation system life. In analyzing the life of the stator winding, which is the heart of the motor, the majority of all winding failures are usually caused by a combination of various stresses acting on the insulation materials and system. In this paper, to evaluate the expected life of traction motor for urban transit E.M.U. it is proposed a new test method of complex accelerating degradation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.449-451
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• 1999

When the traction motor for urban transit E.M.U is driven with VVVF controlled inverter, the insulation degradation factors on the 200 Class insulation system of VPI process are analyzed with considering dielectric, mechanical properties, thermal stability, chemical resistivity and compatibility. A new test method of complex accelerating degradation is proposed to evaluate the insulation reliability and the long-term life including harmonic loss and transient surge stress due to PWM inverter drive.

• Structural Engineering and Mechanics
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• 제82권1호
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• pp.1-16
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• 2022

This work elaborately investigates the influences of the guideway geometry parameters and track irregularity on the dynamic performances of the suspended monorail vehicle-guideway system (SMVGS). Firstly, a spatial dynamic analysis model of the SMVGS is established by adopting ANSYS parameter design language. Then, the dynamic interaction between a vehicle with maximum design load and guideway is investigated by numerical simulation and field tests, revealing the vehicle-guideway dynamic features. Subsequently, the influences of the guideway geometry parameters and track irregularity on the dynamic performances of the SMVGS are analyzed and discussed in detail, and the reasonable ranges of several key geometry parameters of the guideway are also obtained. Results show that the vehicle-guideway dynamic responses change nonlinearly with an increase of the guideway span, and especially the guideway dynamic performances can be effectively improved by reducing the guideway span; based on a comprehensive consideration of all performance indices of the SMVGS, the deflection-span ratio of the suspended monorail guideway is finally recommended to be 1/1054~1/868. The train load could cause a large bending deformation of the pier, which would intensify the car-body lateral displacement and decrease the vehicle riding comfort; to well limit the bending deformation of the pier, its cross-section dimension is suggested to be more than 0.8 m×0.8 m. The addition of the track irregularity amplitude has small influences on the displacements and stress of the guideway; however, it would significantly increase the vehicle-guideway vibrations and rate of load reduction of the driving tyre.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1395-1400
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• 2007

Characteristics of the stress on Continuous Welded Rail(CWR) were investigated to apply to design procedure for railway bridge design. Actions due to change in temperature, braking/traction and bending of the deck were considered in this interaction analysis between CWR and bridge deck. The bridge parameters such as static arrangement of the deck and support stiffness were taken into consideration to examine the influence of the parameters on the additional rail stress. The final results of this study, which include the displacement as well as the stress will be presented in the form of the design chart in future.