• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.125-133
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• 2002

In this study, it was investigated about endurance limit and fatigue behavior of load carrying fillet welded cruciform joints according to welding methods of SMAW, SAW, MIG and FCAW commonly using for welding structures in present. Endurance limit carried omit highly in the order of SMAW, MIG, SAW, FCAW and fatigue crack propagation ratio carried out lowly in the order of SMAW, MIG, FCAW, SAW. By these results, it is needed to use SMAW or MIG welding methods for welding structures with small welding capacity and SAW or FCAW methods for large welding structures after due consideration about economic gains and operation efficiency of welding. Fatigue crack propagation ratio is more effected by strength of welding materials than endurance limit of welding materials according to welding methods.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.1
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• pp.38-44
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• 2003

In this study, endurance limit and fatigue behavior of load carrying fillet welded cruciform joints depending on commonly used welding methods such as SMAW, SAW, MIG and FCAW are investigated. In respect of endurance limit SMAW specimen showes highest result, and then MIG, SAW, FCAW in descending order. However, SMAW specimen showes lowest crack growth rate and it followed by MIG, FCAW, SAW. By these results, it is needed to use SMAW or MIG welding methods for welding structures with small welding capacity and SAW or FCAW methods for large welding structures with respect to economic benefits and operation efficiency of welding. It was also shown fatigue crack growth rate was more influenced by the strenght of welding materials than the endurance limit of welding materials.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.226-227
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• 2005

In this study, it was investigated about endurance and fatigue crack propagation rate of according to welding methods of SMAW and FCAW commonly using for welding structures in present. Endurance limits carried out highly in the order of SMAW, FCAW and fatigue crack propagation rate out lowly in the order of SMAW, FCAW. By these results, it is needed to used SMAW welding methods for welding structures with small welding capacity and FCAW methods for large welding structures after consideration about economic gains and operation efficiency of welding. Fatigue crack propagation rate is more effected by strength of welding materials than endurance limit of welding materials according to welding methods..

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.6
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• pp.763-769
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• 2010

In recent times, there has been considerable interest in HIPS (High Impact Polystyrene) materials for their use in construction of office equipments, home electronics, housing for electronics appliances, packing containers, etc. However, these materials suffer from problems caused by fatigue fracture. Further, their strength is substantially affected by environmental conditions. Therefore, in this study, the effect of temperature was analyzed by performing a tensile test and a fatigue test. It was observed that the yield strength, the ultimate strength, and the fatigue life decreased relatively with an increase in temperature. Further, an S-N curve can be predicted by using the results of the tensile test and a micro-Vickers hardness test.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1345-1351
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• 2010

First, In this essay we research about secondary source unit(SIV)180KVA is install on VVVF direct subways for using Filter Capacitor(FC) maintenance & limit of use. Vehicle's extendly use and congestly at load for Catenary voltage and load change about output change and in SIV unit there are important device named GTO Thyristor, Power Transistor Module device become short and it often happen. We analysis the fault cause and there are effects and we know the secondary source unit in filter capacitor FC1~4 input harmonic distortion component's filtering don't do correctly so we study the capacitor extend use for the component change and the outside condition by slow property changed happen and we check before and when its fault, its difficult to measure. Finally, In this research we care for this reason and we study about capacitor maintenance through control and measure ways improvement and capacitor's life spans limit of use.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.4
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• pp.385-393
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• 2007

The strength evaluation of the most weakest junction part is required for the safety design of all structures. Most of all. in order to enhance the reliability and safety of the welding part. whose use is the highest, it is very important to establish the efficient structure manufacturing technology by studying and investigating the evaluation of fatigue strength in various environments. This study analyzed the relations of da/dN, and th according to the welding methods of SMAW, FCAW, and SAW. In the stage II. the value of stress intensity factor range was the highest in SMAW welding method of stress ration R=0.1, and appeared under the sequence of FCAW and SAW and as the completion section of stress intensity factor was low, threshold stress intensity factor was lowly formed in da/dN - The fatigue life of each welding method is sensitively worked in high stress ratio. judging from the fact that the width of life reduction increases in the high stress ratio zone compared to the width of life reduction in the low stress ratio zone. In the fatigue limit of welding methods before corrosion. the welding of SMAW and FCAW shows the same fatigue limit compared to Base metal, and SAW holds the lowest fatigue limit value.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.5 no.4
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• pp.65-71
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• 2006

The lightness of components required on marine and shipbuilding industry is requiring high strength of components. In particular, fatigue failure phenomena, which happen in metal, bring on danger in human life and property. Therefore, antifatigue failure technology takes an important part on current industries. In this study, it is investigated about endurance and fatigue crack propagation rate of according to welding methods such as SMAW, FCAW and SAW commonly used for welding structures in present. Endurance limits carried out highly in the order of SMAW, FCAW, SAW and fatigue crack propagation rate out lowly in the order of SMAW, FCAW, SAW. By these results, it is needed to use SMAW welding method for welding structures with small welding capacity and FCAW, SAW methods for large welding structures after consideration about economic gains and operation efficiency of welding. Fatigue crack propagation rate is more affected by strength of welding materials than endurance limit of welding materials according to welding methods.

• Magazine of the Korea Concrete Institute
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• v.14 no.2
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• pp.52-60
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• 2002

지하철 구조물과 같은 매스 콘크리트 구조물을 시공할 때 온도 측정을 하는 경우는 많으나 이는 내외부 온도차를 적정한 수준으로 유지하여 균열 발생을 제어하기 위한 수단일 뿐 균열폭을 일정한도 내로 제어할 수 있는 조치는 아니다. 매스 콘크리트 구조물에서 균열폭을 제한 값 이하로 하기 위해서는 적절한 양의 철근을 배치하여야 한다. 또한 시공 이음 등을 작은 간격으로 설치하는 것은 구속도를 완화시키고 온도응력이나 균열폭을 저감시켜 균열 제어상 매우 효과적인 수단이 될 수 있다. 그러나 시공 이음, 균열 유발 줄눈 등의 이음간 간격을 좁히면 내하력 수밀성, 내구성 등에 악영향을 미칠 가능성이 높고, 타설 회수가 많아져 동일한 공정이 반복 투입되므로 시공 속도의 저하 및 공사비 상승 등의 단점이 나타날 수 있다.(중략)

• Tribology and Lubricants
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• v.11 no.4
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• pp.1-12
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• 1995

여러 가지 필수적인 윤활유 성상과 함께 요즘 개발된 엔진에서 요구되는 중요한 특성 중 하나가 윤활유 내의 공기 혼입(aeration) 문제이다. 만일 윤활유 내에 공기가 일정 한도 이상 혼입되면 윤활유가 수행하는 일반 기능 중 하중을 분산시키는 압력 분산 작용과 윤활 작용 및 마찰열을 식혀 주는 냉각 작용이 제대로 되지 않아 엔진 수명과 내구성에 심각한 문제를 초래한다. 특히 현재 밸브 소음 저감 및 정비성 향상을 위해 대부분의 엔진에서 채용하고 있는 hydraulic valve lash adjuster(HLA)에 미치는 영향이 가장 심각하다. HLA는 그 작동 특성이 엔진 오일의 비 압축성을 이용하고 있기 때문에 만일 HLA 내부의 고압실에 공기가 오일에 섞여 들어간다변 밸브 시스템 강성이 떨어지게 되어 오히려 HLA 사용 목적에 반해 밸크 이상 거동에 의한 소음이 유발될 뿐만 아니라 심하면 밸브가 파단되는 심각한 현상이 초래되기도 한다. 상기한 바와 같이 aeration 현상은 경우에 따라 매우 심각한 문제를 유발하기도 하며 엔진이 고속 고출력화 하면서 그 특성은 더욱 관심사가 되어 왔다. 따라서 엔진 각 부분의 올바른 기능과 신뢰성 확보를 위해 aeration의 특징 발생 원인 및 대책을 살펴보고 특히 oil aeration이 HLA와 엔진 베어링에 미치는 영향에 대해 분석 고찰해 봄으로써 그 특성을 이해하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.781-785
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• 2015

In this study, a newly developed ultrasonic fatigue test was performed for durability assessment of polyoxymethylene engineering plastic, which has a high crystallization rate and degree of crystallization. Fatigue strength of POM (polyoxymethylene) was performed on a piezoelectric UFT developed by Mbrosia Co., Ltd(1), operating at a high frequency of 20 kHz. The test results showed a fatigue limit of 5.0~6.0 MPa under fatigue testing at R = -1, 20kHz; and, electron microscopy revealed the size effect by risk volume and fractured dimple structure after the coalescence of micro-voids through the crazing effect, which occurs during the failure of a polymer.