• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년도 춘계 학술대회 개요집
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• pp.21-23
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• 2006

The microstructural investigation and thermo-mechanical reliability evaluation of the Sn-3.0Ag-0.5Cu solder bumped flip chip package were carried out during the thermal shock test of the package. In the initial reaction, the reaction product between the solder and Cu mini bump of chip side was Cu6Sn5 layer, while the two phases which were (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 were formed between the solder and Ni-P layer of the package side. The cracks were occurred at the corner solder joints after the thermal shocks of 400 cycles. The primary failure mechanism of the solder joints in this type of package was confirmed to be thermally activated solder fatigue failure.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.324-327
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• 2003

The needs for the cryocooler which has high reliability and long MTTF are increased in the military and commercial thermal imaging system The gas contamination wear, leakage of the working fluid, fatigue and etc. have the significant effects on the reliability and MTTF(Mean Time To Failure) or MTBF(Mean Time Between Failure) of the Stirling cryocooler. In the KIMM, the Stilting cryocooler with the linear compressor was released after the several performance tests were performed. This paper describe the experimental facility for the MTTF evaluation and some typical results of the Stilling cryocooler.

• 대한기계학회논문집A
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• 제39권10호
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• pp.1039-1044
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• 2015

차량의 개발단계에서 내구성 평가는 많은 시간과 비용이 소요된다. 최근 완성차 업체들은 자사만의 내구성 평가방법을 개발하고 수정 보완하는데 많은 노력을 기울이고 있다. 본 연구는 토션빔 액슬의 내구성 평가를 위한 통합 CAE 기법을 개발함에 있어 세계적인 자동차 업체의 정형화된 CAE 기법과의 비교를 통해 경제성을 평가하고 실험적 방법을 통해 얻은 데이터와의 비교를 통해 신뢰성을 확보하는 것을 목표로 하였다. 이를 위해 현재까지 널리 사용되어 온 준정적 내구해석의 과정 및 결과에서 보완점과 문제점을 분석하였고, 업계의 요구사항을 면밀히 검토하여 정규모드해석을 통해 다물체 동역학 모델을 구성하고 이를 이용한 동역학 해석을 진행한 후 그 결과를 이용하여 내구해석인 공진 내구해석 기법을 제안하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 추계학술발표대회 개요집
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• pp.82-84
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• 2005

Fatigue assessment of welded structure is very sensitive to the method of local stress determination. Normally, hot spot stress which is surface stress extracted from 0.5t, 1.5t away from weld toe is widely used to obtain local stress. However, this method has a lot of limitation in the evaluation of fatigue strength. Therefore, mesh has to comply with strict requirements since stress extracted from this method strongly rely on mesh size and element types. And that method does not cover the stress gradient through thickness direction since only surface stress is considered. Recently, new method to obtain local stress is proposed, which is structural stress. This method has an advantage, which is mesh intransitiveness and covering the effect of both bending and axial stress in local area. In this paper, fatigue test data for various welded joints was analyzed to review the reliability of structural stress. As a result, it is verified that S-N curve using structural stress guaranteed single master curve for various joint type and testing condition.

• 생물정신의학
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• 제20권1호
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• pp.6-11
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• 2013

Objectives There are only a limited number of studies on instruments assessing fatigue in university students, although fatigue exerts negative influences on their health and academic performances and fatigue-related complaints are more frequently reported in young adults than middle-aged adults. The aim of this study was to validate the 9-item Fatigue Severity Scale (FSS) among university students including both undergraduate and graduate students in South Korea. Methods A total of 176 university students completed a battery of self-report questionnaires, including the FSS, the Brief Fatigue Inventory (BFI), the Beck Depression Inventory-II (BDI-II), the Beck Anxiety Inventory (BAI), the Medical Outcomes Study Short Form 36 version 2 (MOS-SF36v2), and the Inclusion of Community in the Self Scale (ICS). The data were collected from February of 2012 to June of 2012. The reliability, convergent validity, divergent validity, and exploratory factor analyses were conducted to assess psychometric properties of the FSS. Results The mean FSS score was 3.20 (standard deviation = 1.43). The FSS demonstrated an excellent internal consistency (Cronbach's ${\alpha}$ = 0.93) and item-total correlations ranged from 0.56 to 0.90. Correlations of the FSS with the BFI (r = 0.71, p < 0.01), BDI-II (r = 0.54, p < 0.01), BAI (r = 0.46, p < 0.01), MOS-SF36v2 physical component summary (r = -0.28, p < 0.01), MOS-SF36v2 mental component summary (r = -0.55, p < 0.01), and ICS (Spearman's rho = -0.07, p = 0.33) showed acceptable convergent and divergent validity. Exploratory factor analysis defined one underlying factor (eigenvalue = 5.67) that explained 93.50% of the total variance. Conclusions To the best of our knowledge, this is the first study to investigate reliability and validity of the FSS in university students. The FSS exhibits good psychometric properties for evaluation of fatigue among university students in South Korea. Since the FSS is easy to administer, score, and interpret, it could be a useful tool in research and practice for assessing fatigue among university students.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.371-372
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• 2012

• 대한기계학회논문집
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• 제14권5호
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• pp.1320-1329
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• 1990

본 연구에서는 토크로드의 여러가지 성능시험이 하능한 시험기의 설계와 개발 에 관하여 논하려 한다. 토크 로드의 정적 성능은, 반경방향 스프링 특성시험 및 비 틀림 방향 스프링 특성시험 그리고 회전토크 특성시험 등을 통하여 평가된다. 그러 나, 이들 세가지 성능시험을 위한 시험기를 각각 개발할 경우 소요비용이 과다해진다. 따라서, 한정된 예산과 시험기 개발후 시험평가 공정의 간소화 등을 고려하여, 본 시 험기는 3대의 시험기로써 하여야 할 기능을 한대의 시험기로써 할수 있도록 개발하였 다. 시험기 개발에 따른 기술적인 고찰과, 본 시험기로 정하중에서의 토크 로드 부 품의 성능시험을 수행하고 서어보 유압식 구조물 피로 시험기를 사용하여 동 부품의 피로 내구성 시험을 실시하고, 고무의 조성변화, 접착성 개선 등을 통해 내구성을 향 상시킴으로 국산화 개발을 가능케 한 기술적 내용들을 살펴 보고자 한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.148-153
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• 2004

This paper represents that parts of a large generator operating in 1000 MW are affected by centrifugal forces due to high-speed rotation in 3600 rpm and 3D FEM Analyses are required to obtained the structural reliability of the generator. From these results, one would know the weakest locations and the stress distributions. The fatigue life is calculated in order to grasp the remaining life of generator. 2D and 3D analyses are performed to calculate stresses of the generator rotor and the retaining ring. From 2D results, we find the SCF at the slot and sub-slot of the rotor. 3D analysis is applied at the end part of generator rotor, which represents complex geometry, and rotor and retaining ring shrink thermally. With these results, designers of rotor and retaining ring can compare with the results of design code and verify the stress distributions of generator rotor and retaining ring, and then calculate the remaining life from the low-cycle fatigue data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.154-159
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• 2004

In this study, in order to perform more efficiently reliability design and integrity assessment of structural members, the relational database management program on the engineering plastics was constructed. This program contained 476 grades for 14 kinds of the engineering plastics and was developed using MS-access and MS-visualbasic. This program consists of 3 modules; search condition, probabilistic characteristics of material property, evaluation of P-S-N curve. We perform fatigue test for probabilistic durability analysis and this results input the database program to estimate P-S-N.

• 복합신소재구조학회 논문집
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• 제6권3호
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• pp.50-61
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• 2015

This paper presents on the structural behavior of the the methyl methacrylate monomer (MMA) double wide flanged the glass fiber-reinforced polymer(GFRP) pipe composite structures for the manhole raise. The evaluation of structural performance on this composite structure was conducted by the axial load, fatigue load, and ultimate load test. The assessment indicates that the MMA double wide flanged GFRP pipe composite structures was confirmed safety, durability and reliability in result as expected. It was found that this composite structure was able to short working times to around 30-50% and construction costs to around 10-23% with compare other construction methods. Also, environmental pollution and civil complaints will be prevented because there will be no longer any noises, vibrations, dust, or construction wastes.