• Journal of Power Electronics
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• 제16권5호
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• pp.1843-1850
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• 2016

This study focused on predicting the fatigue life of an insulated gate bipolar transistor (IGBT) power module for electric locomotives. The effects of different wiring technologies, including aluminum wires, copper wires, aluminum ribbons, and copper ribbons, on solder fatigue life were investigated to meet the high power requirement of the IGBT module. The module's temperature distribution and solder fatigue behavior were investigated through coupled electro-thermo-mechanical analysis based on the finite element method. The ribbons attained a chip junction temperature that was 30℃ lower than that attained with conventional round wires. The ribbons also exhibited a lower plastic strain in comparison with the wires. However, the difference in plastic strain and junction temperature among the different ribbon materials was relatively small. The ribbons also exhibited different crack propagation behaviors relative to the wires. For the wires, the cracks initiated at the outmost edge of the solder, whereas for the ribbons, the cracks grew in the solder layer beneath the ribbons. Comparison of fatigue failure areas indicated that ribbon bonding technology could substantially enhance the fatigue life of IGBT modules and be a potential candidate for high power modules.

• 한국항공우주학회지
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• 제31권3호
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• pp.95-100
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• 2003

위성에서 사용되는 전자장비는 고신뢰성을 요구하고 있으며 예비부품을 보유함으로써 어느 정도의 심각한 결함에도 면역(Immune)되도록 설계되어야 한다. 통신위성은 통상 15년의 임무기간을 가지고 있으므로 위성에서 사용되는 전장 부품은 결함에 대한 분석이 수행되어야 한다. 본 논문은 명령 처리기의 결함 허용 설계와 그에 따른 신뢰도 예측값들은 무궁화 위성3호 자료와 다목적 위성 1호 자료를 참고하였다. 결함 허용 설계에는 많은 Trade-off연구가 필요하나 특히 결함 시나리오에 가장 적합한 결함 허용 방식을 선정하는 것이 중요하다고 할 수 있다.

• 대한기계학회논문집A
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• 제25권2호
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• pp.296-303
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• 2001

Kachanov-Rabotnov(K-R) creep damage theory was reviewed, and applied to design a creep curve for type 316LN stainless steel. Seven coefficients used in the theory, i.e., A, B, k, m, λ, r, and q were determined, and their physical meanings were analyzed clearly. In order to quantify a damage parameter ($\omega$), cavity amount was measured in the crept specimen taken from interrupted creep test with time variation, and then the amount was reflected into K-R damage equations. Coefficient λ, which is regarded as a creep tolerance feature of a material, increased with creep strain. Mater curve with λ=2.8 was well coincided with an experimental one to the full lifetime. The relationship between damage parameter and life fraction was matched with the theory at exponent ${\gamma}$=24 value. It is concluded that K-R damage equation was reliable as the modelling equation for type 316LN stainless steel. Coefficient data obtained from type 316LN stainless steel can be utilized for life prediction of operating material.

• 방사성폐기물학회지
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• 제14권1호
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• pp.11-19
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• 2016

This paper focuses on the estimation of durability and service-life of reinforced concrete structures in Wolsong Low- and intermediate-level wastes Disposal Center (WLDC) in Korea. There are six disposal silos located in the saturated environment. The silo concrete is degraded due to reactions with groundwater and chemical attacks, and finally it will lose its properties as a transport barrier. The infiltration of sulfate and magnesium, leaching of potassium hydroxide, and chlorine induced corrosion are the most significant factors for degradation of reinforced concrete structure in underground environment. From the result of evaluation of the degradation time for each factor, the degradation rate of the reinforced concrete due to sulfate and magnesium is $1.308{\times}10^{-3}cm/yr$, and it is estimated to take 48,000 years for full degradation while potassium hydroxide is leached in depth of less than 1.5 cm at 1,000 years after the initiation of degradation. In case of chlorine induced corrosion, it takes 1,648 years to initiate corrosion in the main reinforced bar and 2,288 years to reach the lifetime limit of the structural integrity, and thus it is evaluated as the most significant factor.

• Elastomers and Composites
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• 제47권3호
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• pp.201-209
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• 2012

그로멧은 자동차의 고무부품들 중의 하나로 에틸렌 프로필렌 고무로 구성되어 있으며, 고무의 비선형 초탄성 성질은 고무제품의 거동을 예측하는데 중요하다. 본 논문에서는, 일축인장시험과 이축인장시험을 통하여 안정된 응력-변형률 관계를 구하고 그로멧에 대한 유한요소해석을 수행하였고, 수명예측을 위한 노화시험을 소개하였다.

• 대한임베디드공학회논문지
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• 제13권3호
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• pp.143-149
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• 2018

It has become ever harder to design reliable circuits with each nanometer technology node; under normal operation conditions, a transistor device can be affected by various aging effects resulting in performance degradation and eventually design failure. The reliability (aging) effect has traditionally been the area of process engineers. However, in the future, even the smallest of variations can slow down a transistor's switching speed, and an aging device may not perform adequately at a very low voltage. Therefore, circuit designers need to consider these reliability effects in the early stages of design to make sure there are enough margins for circuits to function correctly over their entire lifetime. However, such an approach excessively increases the size and power dissipation of a system. As the impact of reliability, new techniques in designing aging-resilient circuits are necessary to reduce the impact of the aging stresses on performance, power, and yield or to predict the failure of a system. Therefore, in this paper, a novel low power on-chip self-tuning circuit considering the aging effects has been proposed.

• Journal of Power Electronics
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• 제16권1호
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• pp.217-226
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• 2016

A new method is proposed based on a hidden Markov model (HMM) to estimate and analyze battery states of health. Battery system health states are defined according to the relationship between internal resistance and lifetime of cells. The source data (terminal voltages and currents) can be obtained from vehicular battery models. A characteristic value extraction method is proposed for HMM. A recognition framework and testing datasets are built to test the estimation rates of different states. Test results show that the estimation rates achieved based on this method are above 90% under single conditions. The method achieves the same results under hybrid conditions. We can also use the HMMs that correspond to hybrid conditions to estimate the states under a single condition. Therefore, this method can achieve the purpose of the study in estimating battery life states. Only voltage and current are used in this method, thereby establishing its simplicity compared with other methods. The batteries can also be tested online, and the method can be used for online prediction.

• Interaction and multiscale mechanics
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• 제4권1호
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• pp.35-47
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• 2011

A global-local finite element modeling technique is employed in this paper to predict the fatigue life of radial truck tires. This paper assumes that a flaw exists inside the tire, in the local model. The local model uses an FEM fracture analysis in conjunction with a global-local technique in ABAQUS. A 3D finite element local model calculates the energy release rate at the belt edge. Using the analysis of the local model, a study of the energy release rate is performed in the crack region and used to determine the crack growth rate analysis. The result considers how different driving conditions contribute to the detrimental effects of belt separation in truck tire failure. The calculation of the total mileage on four sizes of radial truck tires has performed on the belt edge separation. The effect of the change of belt width design on the fatigue lifetime of tire belt separation is discussed.

• Elastomers and Composites
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• 제40권2호
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• pp.119-127
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• 2005

고무부품의 신뢰성을 확보하기 위해서 고무재료의 물성파악과 수명평가는 매우 중요하다 하겠다. 본 연구에서는 냉장고 콤프레샤 모터에서 발생되는 소음 및 진동 제어 목적으로 고무마운트에 사용되는 고무재료인 NBR과 EPDM에 대해 상온과 $70^{\circ}C,\;85^{\circ}C,\;100^{\circ}C$에서 75일 동안 노화시킨 상태에서 단축 인장과 이축 인장으로 물성시험을 수행하여 가교밀도, 100% 모듈러스 변화와 응력-변형률 관계를 파악하였다. 또한, 고무소재의 노화수명을 예측하기 위해 가속열 노화시험을 수행하여 시간-온도 환산식인 아레니우스 관계식을 구하였다.

• Advances in concrete construction
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• 제8권1호
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• pp.55-64
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• 2019

Chloride corrosion has become the main factor of reducing the service life of reinforced concrete structures. The object of this paper is to propose a theoretical model that predicts the service life of chloride-corrosive concrete under fatigue load. In the process of modeling, the concrete is divided into two parts, microcrack and matrix. Taking the variation of mcirocrack area caused by fatigue load into account, an equation of chloride diffusion coefficient under fatigue load is established, and then the predictive model is developed based on Fick's second law. This model has an analytic solution and is reasonable in comparison to previous studies. Finally, some factors (chloride diffusion coefficient, surface chloride concentration and fatigue parameter) are analyzed to further investigate this model. The results indicate: the time to pit-to-crack transition and time to crack growth should not be neglected when predicting service life of concrete in strong corrosive condition; the type of fatigue loads also has a great impact on lifetime of concrete. In generally, this model is convenient to predict service life of chloride-corrosive concrete with different water to cement ratio, under different corrosive condition and under different types of fatigue load.