• Journal of Welding and Joining
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• v.25 no.1
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• pp.63-69
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• 2007

Once assessment of material failure characteristics is captured precisely in a unified way, it can bedirectly incorporated into the structural failure assessment under various loading environments, based on the theoretical backgrounds so called Local Approach to Fracture. The aim of this study is to develop a numerical fatigue test method by continuum damage mechanics applicable for the assessment of structural integrity throughout crack initiation and structural failure based on the Local Approach to Fracture. The generalized elasto-visco-plastic constitutive equation, which can consider the internal damage evolution behavior, is developed and employed in the 3-D FEA code in order to numerically evaluate the material and/or structural responses. Explicit information of the relationships between the mechanical properties and material constants, which are required for the mechanical constitutive and damage evolution equations for each material, are implemented in numerical fatigue test method. The material constants selected from constitutive equations are used directly in the failure assessment of material and/or structures. The performance of the developed system has been evaluated with assessing the S-N diagram of stainless steel materials.

• Fire Science and Engineering
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• v.18 no.4
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• pp.72-77
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• 2004

In this paper, we studied on the short-circuit process, surface structure, and component variation of vinyl cords. In the results of high speed imaging system (HSIS) analysis, as soon as wire covering was damaged by heat, the conductor of wire came in contact with the other conduct of wire, and the short-circuit occurred. Stereomicroscope and SEM analysis indicated that the source part of wire showed V-type form. The molten beads of load part were bigger than those of source part. In the results of EDX analysis, Cu and O were detected in the source part, whereas covering material (Cl, Ca), Cu and O were detected in the load part. The results will help us to find out the cause of electrical fire.

• Journal of the Korean Society of Safety
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• v.30 no.3
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• pp.7-12
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• 2015

CFRP composites are used as primary structural members in various industrial fields because their specific strength and specific stiffness are excellent in comparison to conventional metals. Their usage is expanding to high added-value industrial fields because they are more than 50% lighter than metals, and have excellent heat resistance and wear resistance. However, when CFRP composites suffer impact damage, destruction of fiber and interface delamination occur. This causes an unexpected deterioration of strength, and for this reason it is very difficult to ensure the reliability of the excellent mechanical properties. Therefore, for the destruction mechanism in bending with impact damage, this study investigated the reinforcement data regarding various external loads by identifying the consequential strength deterioration. Specimens were damaged by impact with a steel ball propelled by air pressure. Decrease in bending strength caused by the tension and compression of the impact side, and depending on the lamination direction of fiber and interface inside the specimen. From the bending test it was found that the bending strength reduced when the impact energy increased. Especially in the case of compression on the impact side, as tensile stress occurred at the damage starting point, causing rapid failure and a substantially reduced failure strength.

• The Korean Nurse
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• v.9 no.2 s.46
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• pp.29-33
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• 1970

이 책자는 기본간호의 구성요소를 분석한 것이며 이것은 간호원의 독특한 기능에 관한 다음과 같은 정의에서부터 나온 것이다. 즉 간호는 각개인이 병에 걸려 있거나 혹은 건강할때, 건강이나 질병으로부터의 회복(혹은 평화스러운 죽엄으로)에 도움이 되는 모든 활동을 수행함에 있어서 그를 돕는 일이며 이러한 일들은 만일 그가 필요한 힘, 의지 또는 지식을 가지고 있었다면 다른 사람의 도움없이도 할 수 있었을 것이다. 또한 각 개인이 가능한 한 속히 독립성을 회복하도록 돕는 일도 간호원의 기능인 것이다. 다시 말하면 간호원은 각개인이 다음과 같은 활동을 할 수 있도록 돕는것이다. (1) 정상적으로 호흡한다; (2) 적절하게 먹고 마신다; (3) 모든 배설통로를 통하여 배설한다; (4) 적당한 자세를 유지하고, 운동한다;(걷는 것, 눕는 것, 한 체위에서 다른 체위로 바꾸는 것); (5) 잠자고 휴식한다; (6) 적당한 의복을 선택학, 옷을 입고, 옷을 벗는다; (7) 의복을 적당히 조정하고 환경을 조절함으로써 체온을 정상적으로 유지하도록 한다; (8) 신체를 청결하게, 몸을 단정히 하고 표피를 보호한다; (9) 환경으로부터 오는 위험을 피하고 다른 사람을 손상케 하는 위험을 방지하다록 한다; (10) 감정, 욕구, 공포, 또는 ''느낌''을 표현할 때 다른 사람들과 의사를 소통한다; (11) 그의 신앙에 따라서 예배한다; (12) 성취감을 가져올 수 있는 어떤 작업을 한다; (13) 유희, 또는 각종 오락에 참여한다; (13) 건강한 생활로 ''정상적'' 발전을 할 수 있게 만드는 방법을 배우고, 발견하고 또는 호기심을 만족시킨다.

• 한국정보통신설비학회:학술대회논문집
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• 2002.08a
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• pp.17-20
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• 2002

본 논문에서는 세라믹 칩 안테나를 LTCC로 구현하여 다중 대역 특성을 얻는 방법을 제안하고 있다. 휴대용 단말기에 칩 안테나를 내장함으로 물리적 손상을 피하고 위치추적 시스템(GPS) 대역과 단말기 송수신용 대역, 즉 두 대역 이상 사용 가능하고 ${\varepsilon}_r=7.8$인 세라믹 칩 안테나를 LTCC(Low Temperature Co-fired Ceramic)공정을 이용하여 세라믹 칩 내부에 정합 회로를 구현하여 이중 대역 특성을 갖는 구조에 대해 논의하고 있다. 안테나의 전체 크기는 $16mm{\times}4mm{\times}2mm$ 이며 대역폭은 삽입손실 -10dB 기준 대략 1560MHz에서 2160MHz까지 약 600MHz정도이다. 측정은 접지면의 넓이가50mmx50mm이고 두께=0.7874mm, ${\varepsilon}_r=4.6$인 FR4 기판을 이용하여 측정한다.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.280-287
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• 2008

In case of low pressure steam turbine used in power plant, it was operated in wet steam and high stress condition. Therefore, it is possible that the corrosion damage of low pressure was induced by this condition. According to previous study, about 30% of total blade failure correspond to corrosion fatigue or SCC(stress corrosion cracking) in low pressure turbine. Especially, LSB(last stage bucket) of low pressure turbine has a higher hardness to prevent erosion damage due to water droplet however, generally this is more dangerous for SCC damage. Therefore, to improve reliability of turbine blade. various methods for SCC evaluation has been developed. In this study, the crack found in LSB during in-service inspection was evaluated using microstructure analysis and stress analysis. From the stress analysis, the optimum size of fillet to remove the crack was proposed. And also, the reliability was evaluated for modified LSB using GOODMAN diagram.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.381-388
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• 2003

The material deficiencies in the form of pre-existing defects can initiated cracks and fractures. The stress distribution and fatigue crack initiation life of engineering materials may be associated with the size, the shape and the relative location of defects contained in the component. The objective of this study is to investigate the effect of arbitrarily located hole defect around the rivet hole of a wing section in monolithic aluminum and Al/GFRP laminates under cyclic bending moment during a service load. The stress distribution and the fatigue crack initiation behavior near a rivet hole of on the relationships between stress concentration factor ($K_t$) and relative position of defects were considered. The test results indicated the features of different stress field. Therefore, the stress concentration factor ($K_t$) and the fatigue crack initiation behavior was illustrated different behavior according to each position of hole defect around the rivet hole in monolithic aluminum and Al/GFRP laminates.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1127-1132
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• 2003

Suspension system of vehicle have enough endurance during its life time to protect passenger. Spring is one of major part of vehicle. Thus, a fatigue strength evaluation for leaf spring based on road load response was carried out. At first, strain of leaf spring is measured on the city condition and proving ground condition. And next, the damage analysis of road load response data was carried out. And fatigue test of leaf spring were also carried out. Based on -N life relation, fatigue life of leaf spring was evaluated at belgian mode, city mode and drawing test specification. After that, it is compared the design life of leaf spring and evaluated fatigue life by belgian mode, city mode and drawing test specification. From the above, the maximum load-fatigue life relation of leaf spring was defined by test. and new test target of belgian mode and city mode was proposed to accept design specification of leaf spring. It is expect that proposed test target can verify leaf spring fatigue endurance at specific road condition.

• Korean Journal of Materials Research
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• v.17 no.8
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• pp.425-432
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• 2007

The microstructural evolution of ferritic 9Cr-1Mo-V-Nb steel, subjected to creep-fatigue at $550^{\circ}C$, was evaluated nondestructively by measuring the ultrasonic velocity. The variation of the ultrasonic velocity with the fatigue life fraction exhibited three regions. In the first region ($N/N_f$<0.2), a significant increase in the velocity was observed, followed by a slight increase between the fatigue life fractions of $0.2N_f$ and $0.8N_f$, and then a decrease in the final region. The change of the ultrasonic velocity during creep-fatigue was interpreted in relation to the microstructural properties. This study proposes an ultrasonic nondestructive evaluation method of quantifying the level of damage and microstructural change during the creep-fatigue of ferritic 9Cr-1Mo-V-Nb steel.

• Bulletin of the Society of Naval Architects of Korea
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• v.30 no.2
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• pp.31-43
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• 1993

본 연구에서는 힁부재가 없는 AFRAMAX급 신구조 방식의 유조선을 개발하고자 하였다. 설계의 기본 개념은 1) 이중선체구조를 채용하여 해난사고 발생시 기름유출 방지를 피하고, 2) 힁부재가 없는 극히 단순한 선체구조를 채용하여 용접 로봇등을 활용한 자동건조 비율을 높임으로써 건조 생산성을 향상시키는데 주안점을 두고 있다. 설계 결과 얻어진 선체구조는 기존의 유조선 구 조와 매우 상이하다. 초기구조설계단계에서 구조 부재의 치수는 기존의 선급설계 지침을 활용 하여 결정하였으나, 기존의 유조선 구조와 비교하여 구조배치가 크게 바뀌어 졌기 때문에 기존의 선급설계지침을 만족했다고 해서 구성부재와 국부구조뿐만 아니라 구조 전체적으로도 충분한 구조안전성을 가지고 있는지는 확실치 않다. 따라서 직접구조해석에 의한 구조안전성 평가가 필수적으로 요구되며, 이를 위해 저자들은 선체구조의 최종 종강도(ultimate longitudinal strength), 최종 힁강도(ultimate transverse strength) 및 최종 국부강도(ultimate local strength )를 기준으로한 구조안전성 평가를 수행하였다. 본 논문에서는 이들 중에서 국부 구조부재에 대한 안전성평가 문제만을 다루었다. 결론적으로, 본 연구에서 개발한 선체구조는 건전상태(intact condition)하에서 뿐만 아니라 손상상태하에서도 구조부재는 좌굴 또는 붕괴하지 않고 전반적 으로 충분한 구조안전성을 가지고 있다는 결론을 내릴 수 있었다.