• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.101-102
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• 2005

• 한국압력기기공학회 논문집
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• 제9권1호
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• pp.48-55
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• 2013

In this paper, W-DCAP-HTR(Web-based Design Compatibility Assessment Program for High Temperature Reactor) which will be used to check the design criteria for high temperature reactor is newly proposed. To do this, the assessment procedure of the ASME Sec.III Div.5 such as time-dependent primary stress limit, accumulated inelastic strain, and creep-fatigue damage evaluation were investigated. Furthermore, the trend of candidate materials for high temperature reactor was also reviewed. Then, all assessment procedures for high temperature reactor have been computerized to enhance the efficiency and to reduce the possibility of human error during calculating procedure by hand calculation. It can be directly conducted by adopting the actual thermal and structural analysis results. The validation of W-DCAP-HTR has been demonstrated by benchmark analysis.

• 한국정밀공학회지
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• 제16권8호
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• pp.46-52
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• 1999

Large valves for steam turbines of fossil power plants are exposed to a severe mechanical and thermal loading resulting from steam with high pressure and high temperature. Valve casings are designed to withstand such a loading. During the operation of a plant, temperatures at inner and outer surface of the casings are measured and steam flow is controlled so that the measured difference is lower than the maximum allowable value determined in the design stage. In this paper, a method is presented to calculate the maximum allowable temperature difference at the inner and outer surface of valve casings for steam turbines of fossil power plants. The finite element method is used to analyze distribution of temperature and stresses of a casing under the operating condition. Low cycle fatigue and creep rupture are taken into consideration to determine the maximum allowable temperature difference. The method can be usefully applied in the design stage of the large valves for the steam turbines, contributing to safe and reliable operation of the fossil power plants.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1676-1685
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• 2003

Tensile and low cycle fatigue tests on prior cold worked 3l6L stainless steel were carried out at various temperatures ftom room temperature to 650$^{\circ}C$. Fatigue resistance was decreased with increasing temperature and decreasing strain rate. Cyclic plastic deformation, creep, oxidation and interactions with each other are thought to be responsible for the reduction in fatigue resistance. Currently favored life prediction models were examined and it was found that it is important to select a proper life prediction parameter since stress-strain relation strongly depends on temperature. A phenomenological life prediction model was proposed to account for the influence of temperature on fatigue life and assessed by comparing with experimental result. LCF failure mechanism was investigated by observing fracture surfaces of LCF failed specimens with SEM.

• 마이크로전자및패키징학회지
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• 제30권1호
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• pp.17-29
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• 2023

본 논문에서는 전자제품의 소형화와 고성능화에 따라 패키징 기술에서 핵심적인 역할을 하는 솔더 조인트의 신뢰성 평가 방법을 소개한다. 우선, 다양한 합금 조성과 제품 형태에 따른 솔더의 특성을 설명하고, 여러 패키지에서의 솔더 조인트 구조에 대한 개요를 제시한다. 그 다음 솔더 합금의 조성과 미시구조가 솔더의 열적 및 기계적 특성에 미치는 영향을 분석하며, 솔더 크리프 거동에 대해 간략히 소개한다. 이어서, 신뢰성 평가를 위한 크리프 모델과 피로 모델 등을 고려한 분석 기법들을 소개하고, 솔더 조인트의 신뢰성을 향상시킬 수 있는 방안에 대해 논의한다. 본 연구는 반도체 패키징 기술 분야에서 솔더 조인트의 신뢰성 평가와 개선에 유익한 정보를 제공할 것으로 기대된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1056-1061
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• 2003

CD-R disc drive is one of the basic options of personal computer today. In this trend, various CD-R discs can be purchased in every market. Even very low quality discs are in market too. Today's CD-R disc drive is being operated over 10,000 RPM. So the possibility of the disc fracture is growing faster. Sometimes, during the test of a new disc drive by various methods to confirm the quality of it, fracture of the disc happens. And it happens in end user's personal computer scarcely. In this reason, new methods to confirm the quality and the failure mechanism of the optical disc are studied in this paper.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 춘계 기술심포지움 논문집
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• pp.79-84
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• 2002

The bottom-leaded plastic(BLP) packages have attracted substantial attention since its appearance in the electronic industry. Since the solder materials have relatively low creep resistance and are susceptible to low cycle fatigue, the life of the solder joints under the thermal loading is a critical issue for the reliability The represent study established a finite element model for the analysis of the solder joint reliability under thermal cyclic loading. An elasto-plastic constitutive relation was adopted for solder materials in the modeling and analysis. A 28-pin BLP assembly is modeled to investigate the effects of various epoxy molding compound, leadframe materials on solder joint reliability. The fatigue life of solder joint is estimated by the modified Coffin-Hanson equation. The two coefficients in the equation are also determined. A new design for lead is also evaluated by using finite element analysis. Parametric studies have been conducted to investigate the dependence of solder joint fatigue life on various package materials.

• Smart Structures and Systems
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• 제18권6호
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• pp.1203-1215
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• 2016

When strain sensing cables are under long-term stress and cyclic loading, creep may occur in the jacket material and each layer of the cable structure may slide relative to other layers, causing fatigue in the cables. This study proposes a device for testing the fatigue characteristics of three types of cables operating under different conditions to establish a decay model for observing the patterns of strain decay. The fatigue characteristics of cables encased in polyurethane (PU), GFRP-reinforced, and wire rope-reinforced jackets were compared. The findings are outlined as follows. The cable strain decayed exponentially, and the decay process involved quick decay, slow decay, and stabilization stages. Moreover, the strain decay increased with the initial strain and tensile frequency. The shorter the unstrained period was, the more similar the initial strain levels of the strain decay curves were to the stabilized strain levels of the first cyclic elongation. As the unstrained period increased, the initial strain levels of the strain decay curves approached those of the first cyclic elongation. The tested sensing cables differed in the amount and rate of strain decay. The wire rope-reinforced cable exhibited the smallest amount and rate of decay, whereas the GFRP-reinforced cable demonstrated the largest.

• 대한기계학회논문집
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• 제12권6호
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• pp.1320-1326
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• 1988

본 연구에서는 파괴역학적인 해석법과 표면레프리카법을 확장, 적용시켜 피로 -크리프하의 유지시간에 따른 작은 표면균열의 분포상태와 이의 합체, 성장 및 밀도변 화특성을 해석하여 기초적 자료를 얻는다.

• Journal of Welding and Joining
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• 제18권2호
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• pp.227-227
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• 2000

Pressure vessels usually consist of main body and pipes which are connected with the main body. And as joining method of such main body and pipes, welding is carried out. After welding, welding residual stresses inevitably occur around welded joints. As residual stresses act harmfully on fatigue strength, corrosion and buckling strength of structure, PWHT is carried out for the purpose of removing the residual stress. But, during PWHT process, 2 ¼Cr-1Mo steels are frequently apt to generate reheat crack. For this reason, it is strongly needed to analyze and examine the mechanical behavior of welded joints before and after PWHT process. So, in this study, welded nozzle parts of pressure vessel where reheat cracks frequently occur are selected for examining the mechanism of crack-occurrence. (Received December 2, 1999)