• 에너지공학
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• 제29권3호
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• pp.97-102
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• 2020

본 연구에서는 화재가 발생하였을 때 작동되는 옥외형 피난계단 구조물이 태풍에 따른 풍압이 작용하였을 때 내구성을 검증하기 위하여 단방향 유동-구조 연성해석을 진행하였다. 이를 위해, 피난계단 구조물 주위에 대한 유동장을 정상상태로 유동해석을 수행하였고, 이러한 해석결과를 구조해석을 위한 입력 데이터로 사용하여 구조응력, 변형량, 피로수명 등의 계산을 통해 내구성을 분석하였다. 유동해석 결과, 피난계단 구조물 형상에 따라 공기에 의한 유동 흐름이 다르게 나타났으며, 이러한 유동속도 분포는 구조물 표면에 전압력으로 작용하였다. 또한, 이러한 전압력에 의해 계산된 구조해석 결과, 최대응력값으로 계산된 안전율이 허용치 이상으로 나타났으며, 피로수명과 변형량 분석을 통해 내구성을 입증하였다.

• Korean Chemical Engineering Research
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• 제60권3호
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• pp.321-326
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• 2022

고분자 전해질 연료전지(PEMFC) 성능과 가격인하를 위해 고분자막의 두께가 얇아지는 추세에서 내구성을 향상시키는 연구가 더욱 중요하게 되었다. 고분자막의 내구성 평가에서 기계적 내구성 평가시간이 화학적 내구성 평가시간보다 2배 이상 소요되므로 내구성 평가 조건을 잘 선택하는 것이 필요하다. 본 연구에서는 기계적 내구 평가 프로토콜(Wet/Dry)에서 유입가스 종류와 유량에 차이가 있을 때 기계적 내구 평가시간이 얼마나 변하는지 확인하고자 하였다. 2,000 mL/min 유량에서 질소를 사용했을 때 평가시간이 공기를 사용했을 때보다 1.25배 증가했다. 공기 사용시 전극 Pt의 열화속도가 증가하는 것이 주 요인이었다. 유량이 800 mL/min 으로 감소하면 공기와 질소 평가시간이 각각 1.5배, 1.2배 증가했다.

• 터널과지하공간
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• 제25권1호
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• pp.86-96
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• 2015

본 연구에서는 암반비탈면의 성능기반 평가방안을 개발하기 위해 델파이 기법을 이용하여 성능별 평가항목을 도출하였으며, 요인분석을 통해 최종 평가항목의 타당성을 검증하였다. 비탈면의 성능은 상태건전성, 안전성 그리고 내구성으로 분류하였다. 델파이 조사를 통해 상태건전성에는 절리방향, 배수조건 등 17개의 평가항목이 도출되었으며, 안전성에는 낙석발생 가능성, 인명피해 규모 등 4개의 평가항목이 도출되었다. 내구성에는 풍화도를 포함한 3개의 평가항목이 도출되었다. 델파이 조사를 통해 도출된 24개의 평가항목에 대해 탐색적 요인분석(EFA)을 실시한 결과, 24개의 평가항목 모두 타당성을 확보하고 있는 것으로 나타났다. 또한, 탐색적 요인분석 결과에 따라 3가지의 성능유형을 내적 상태건전성, 외적 상태건전성, 위험도, 피해도 그리고 지반 및 보호/보강시설의 내구성으로 세분류하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1131-1137
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• 2004

With the recent continuous expansion of subways, newly created subways tend to have lower locations and wider sections. Furthermore. since box structures and evacuating tunnels are classified into a category of mass-concrete. the thermal-stress, emitted from the inside. causes cracks to structures from the inception of constructing. In this paper, thermal-stress analysis and durability evaluation of box structure were carried out to investigate relationship between durability and parameter causing the heat of hydration. Through the examination, this paper tries to find out satisfactory solutions to regulated thermal crack and ensure the required duration period. The results of this paper showed that to control thermal crack and guarantee the required duration period it was more effective to use low-heat-portland cement and moderateheat-portland cement. As cement volume due to reduction of water-cement ratio increased, the possibility of thermal cracks occurrence increased but results of durability evaluation was different depending on evaluation method. The results showed that the appropriate water-cement ratio to control the heat of hydration and satisfy the required durability was $45\∼55\%$. And it was showed that during placement of concrete blocks ambient temperature affect the heat of hydration. thermal crack and long-term durability largely and when concrete was placed at low temperature to control thermal crack. it need to try to guarantee the required duration period. Henceforth, by studying not only internal and external conditions, such as the relative humidity and the unit weight. but also methods, to evaluate durability, in accordance with domestic situations, more reasonable design of durability should be achieved.

• 한국가구학회지
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• 제28권2호
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• pp.111-117
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• 2017

Recently, as people's interest in wood has increased, the use of wood as household and landscape decking materials has increased. As the deck material, imported wood such as synthetic wood, Ipe, and Malas was used in addition to the existing preserved wood, but recently deck use has been activated as part of the activation of domestic materials. As an important quality factor in the selection of such decking materials, various durability along with weatherability for long - term use is required for maintenance. Generally used tropical hardwoods have excellent weatherability and durability without additional preservative treatment. However, the domestic larch is a wood species with a higher specific gravity and durability than ordinary conifers. However, it has not yet been used as a deck material due to lack of comparative studies on its characteristics. Therefore, hardness and durability of wood were measured using six specimens of Ipe, Massaranduba, Malas, Douglas-fir, Larch and Torrefied-Larch. Density Profile was used to measure the density, and Brinell hardness test and resistance test against momentary impact were carried out for the test of resistance to static load. Also, The hardness and durability of wood were measured by castor test with resistance test against dynamic load, as well as, nail down test by experiment on surface hardness and durability. As a result of the experiment, the hardness was increased in proportion to the density, and it was confirmed that the imported lumber was harder and durable than the domestic larch.

• Advances in concrete construction
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• 제5권4호
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• pp.313-330
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• 2017

Geopolymer is a sustainable concrete, replaces traditional cement concrete using alternative sustainable construction materials as binders and alkaline solution as alkaline activator. This paper presents the strength characteristics of geopolymer concrete (GPC) developed with fly ash and GGBS as binders, combined Sodium silicate ($Na_2SiO_3$) and Sodium Hydroxide (NaOH) solution as alkaline activators. The parameters considered in this research work are proportions of fly ash and GGBS (70-30 and 50-50), curing conditions (Outdoor curing and oven curing at $600^{\circ}C$ for 24 hours), two grades of concrete (GPC20 and GPC50). The mechanical properties such as compressive strength, split tensile strength and flexural strength along with durability characteristics were determined. For studying the durability characteristics of geopolymer concrete 5% $H_2SO_4$ solutions was used and the specimens were immersed up to an exposure period of 56 days. The main parameters considered in this study were Acid Mass Loss Factor (AMLF), Acid Strength Loss Factor (ASLF) and products of degradation. The results conclude that GPC with sufficient strength can be developed even under Outdoor curing using fly ash and GGBS combination i.e., without the need for any heat curing.

• 한국수소및신에너지학회논문집
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• 제26권5호
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• pp.493-498
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• 2015

The fuel cell vehicle is a type of hydrogen vehicle which uses a fuel cell to produce electricity, powering its on-board electric motor. The fuel cell vehicle driving principle is completely different from the internal combustion engine vehicle. In order to ensure the durable quality of the fuel cell vehicle, durability test mode considering the characteristics of the fuel cell must be developed. In this study, we derived the durability test mode profile through collecting and analyzing fuel cell vehicle driving data. Then, the accelerated durability test mode is developed by adding degradation conditions and is experimentally validated to have an acceleration factor of 5~6.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.32-38
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• 2004

To evaluate the durability of direct injection diesel engine using biodiesel fuel, a small D. I. diesel engine was operated on a blend(BDF 20) of 20％ biodiesel fuel and 80％ diesel fuel for 200 hours. Engine dynamometer test was performed at a load of 90％ and a speed of 1900 rpm to monitor the engine performance and exhaust emissions. Engine performance parameters and exhaust emissions were sampled at 1 hour interval for analysis. The combustion maximum pressure and the crank angle at this maximum pressure as a combustion variation factor were considered to study the combustion characteristics of BDF 20 in diesel engine during durability test. As the results, the standard deviations and errors of combustion variation factors on BDF 20 were very little and combustion characteristics were very stable during the durability test. BDF 20 resulted in lower emissions of carbon monoxide, carbon dioxide, and smoke emissions with special increase of nitrogen oxides compared to diesel fuel. There was no also unusual change in engine oil composition from using BDF 20. Most of engine parts were clean and showed little wear, but soots were detected around the hole of fuel injector when BDF 20 was used in direct injection diesel engine for 200 hours.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.225-230
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• 2005

This paper describes determination of optimal lubricant quantity for driving gear unit. The purpose of selecting optimal lubricant quantity is to evaluate durability of driving gear unit. Lubricant quantity of driving gear unit is important factor affecting durability. The determination methode of lubricant quantity evaluation is used calculation necessary lubricant quantity first, then selection of optimal oil quantity as a base for moving of oil temperature according to changing oil quantity.

• 한국항공우주학회지
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• 제47권1호
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• pp.35-40
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• 2019

본 연구의 목적은 항공기 구조개발에 널리 적용되고 있는 탄소섬유 복합재의 피로특성을 확인하고, 실기체 피로시험에 활용되고 있는 자료를 획득하는 것이다. 복합재 구조의 내구성 및 손상허용성의 평가는 주로 피로시험을 통하여 이루어지며, 실기체 피로시험에 적용되고 있는 파라미터에는 피로수명계수와 하중증대계수가 있다. 탄소섬유/에폭시 일방향 및 직물형 복합재로 시편을 제작하였으며, 응력비와 적층패턴을 달리하여 피로시험을 수행하였다. Sendeckyj 모델을 적용한 와이블 분포와 개별적인 피로수명에 대한 와이블 분포를 이용하여 형상 파라미터를 분석하였다. 또한 신뢰도를 고려한 피로수명계수와 하중증대계수를 평가하였다.