• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
• /
• pp.225-226
• /
• 2002

In this work, the friction and wear behavior under' various lubrication regimes were investigated. The objective of this work is to develop an Accelerated Life Test (ALT) method for the durability evaluation of a machine element which is operated under lubrication. Electric contact resistance and frictional forces were measured with respect to a wide range of the loads and speeds under various lubrication regimes using a pin-on-disk type tribotester. From the experimental results, it could be found that an effective and reliable ALT method could be achieved by controlling the lubrication regime through the measurements of friction coefficient and contact resistance with respect to load and sliding speed.

• 품질경영학회지
• /
• 제24권4호
• /
• pp.29-43
• /
• 1996

This paper identifies these data by the data diagnosis in lognormal distribution and presents the method to obtain exact parameter estimates and confidence intervals of regression line. The life-stress relationship uses Arrhenius model and life data generate Class-H insulation complete data by simulation. Also, the method to estimate parameters uses least squares estimation and externally Studentized residuals can be used as test statistics for identifing outliers. And influential cases are identified by Cook's distance. This research is intended to obtain the useful information for the life of products and test method, to save time and costs, and to help optimum accelerated life test plans.

• 대한기계학회논문집A
• /
• 제39권4호
• /
• pp.397-403
• /
• 2015

본 논문은 개발 중에 있는 굴삭기 무인조종 로봇을 대상으로 시스템 신뢰도 평가 방법을 제안하고, 제안한 방법을 이용하여 수행한 신뢰도 보증시험에 대한 결과를 나타낸다. 로봇 시스템은 위험한 작업환경에서 작업자의 안전을 위하여 개발되었으며 전체 시스템의 신뢰도는 각 구성품의 신뢰도로부터 계산될 수 있다. 따라서 세 가지 주요 구성품 각각에 대한 전용 시험 장비를 제작하여 가속수명시험에 사용하였다. 가속수명시험 결과를 이용하여 신뢰수준에 따른 보증할 수 있는 평균수명을 추정하고, 적은 시료 수를 사용하는 시스템 신뢰도 보증 시험법을 제안하였다.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제12권2호
• /
• pp.67-78
• /
• 2012

An electric double-layer capacitor(EDLC) is an electrochemical capacitor with relatively high energy density, typically hundreds of times greater than conventional electrolytic capacitors. EDLCs are widely used for energy storage rather than as general-purpose circuit components. They have a variety of commercial applications, notably in energy smoothing and momentary-load devices, and energy-storage and kinetic energy recovery system devices used in vehicles, etc. This paper presents an accelerated degradation test of an EDLC with rated voltage 2.7V, capacitance 100F, and usage temperature $-40^{\circ}C{\sim}65^{\circ}C$. The EDLCs are tested at $50^{\circ}C$, $60^{\circ}C$, and $70^{\circ}C$, respectively for 1,750hours, and their capacitances are measured at predetermined times by constant current discharge method. The failure times are predicted from their capacitance deterioration patterns, where the failure is defined as 30% capacitance decrease from the initial one. It is assumed that the lifetime distribution of EDLC follows Weibull and Arrhenius life-stress relationship holds. The life-stress relationship, acceleration factor, and $B_{10}$ life at design condition are estimated by analyzing the accelerated life test data.

• 신재생에너지
• /
• 제17권2호
• /
• pp.24-31
• /
• 2021

Renewable energy has become more popular with the increase in the use of solar power. Consequently, the disposal of defective and old solar panels is gradually increasing giving rise to a new problem. Furthermore, the efficiency and power output decreases with aging. Researchers worldwide are engaged in solving this problem by developing eco-module technologies that restore and reuse the solar panels according to the defect types rather than simple disposal. The eco-module technology not only solves the environmental problem, but also has economic advantages, such as extending the module life. Replacement of encapsulants contributes to a major portion of the module maintenance plan, as the degradation of encapsulants accounts for 60% of the problems found in modules over the past years. However, the current International Electrotechnical Commission (IEC) standard testing was designed for the commercialization of solar modules. As the problem caused by long-term use is not considered, this method is not suitable for the quality assurance evaluation of the eco-module. Therefore, to design a new accelerated test, this paper provides an overview of EVA degradation and comparison with the IEC and accelerated tests.

• Nuclear Engineering and Technology
• /
• 제56권4호
• /
• pp.1244-1249
• /
• 2024

A combination of flow-accelerated corrosion (FAC) tests and corresponding computational fluid dynamics (CFD) tests were performed to determine the hydrodynamic parameters that could help predict the highly susceptible location to FAC in the elbow section. The accelerated FAC tests were performed on a specimen containing elbow sections fabricated using commercial 2-inch carbon steel pipe. The tests were conducted at flow rates of 9 m/s under the following conditions: water temperature of 150 ℃, dissolved oxygen <5 ppb, and pH 7. Thickness reduction of the specimen pipe due to FAC was measured using ultrasonic testing. CFD was conducted on the FAC test specimen, and the turbulence intensity, and shear stress were analyzed. Notably, the location of the maximum hydrodynamic parameters, that is, the wall shear stress and turbulent intensity, is also the same location with maximum FAC rate. Therefore, the shear stress and turbulence intensity can be used as hydrodynamic parameters that help predict the FAC-induced wall-thinning rate. The results provide a method to identify locations susceptible to FAC and can be useful for determining inspection priority in piping systems.

• 대한기계학회논문집A
• /
• 제41권10호
• /
• pp.997-1004
• /
• 2017

엘리베이터 와이어로프의 수명은 제품의 매우 중요한 특성 가운데 하나로서 사용자의 안전 및 장비의 정비 정책과 밀접한 관계가 있다. 엘리베이터 와이어로프의 수명을 사용조건에서 측정하는 것은 매우 비경제적이다. 이 연구에서는 엘리베이터 와이어로프 (8x19W-IWRC)의 가속열화시험 데이터를 활용하여 와이어로프의 수명을 추정하는 방법을 다루었다. 굽힘피로시험기를 이용하여 가속열화시험을 진행하였으며 가속변수로는 인장하중을 사용하였다. 와이어로프의 수명은 대수정규분포를 가정하였고, 선형회귀모형을 이용하여 가수명을 구한 후 가속수명모형을 이용하여 와이어로프의 수명을 추정하는 방법과 고장 확률에 대한 로지스틱 회귀모형을 이용하여 추정하는 방법을 제시하고 두 모형의 수명 추정결과를 비교하였다.

• 한국군사과학기술학회지
• /
• 제14권6호
• /
• pp.1186-1191
• /
• 2011

Composition which was used as a white smoke grenade consists of Aluminium(Al), Hexachloroethane(HCE) and Zinc Oxide(ZnO), etc. there is a possibility of misfire due to long term storage and there are very few reports on the mechanism behind misfire. In this study, an experimental method known as accelerated degradation testing is used to investigate the chemical mechanism resulting in misfire. The mechanism of chemical change during long term storage was analyzed with XRD and FT-IR. Analysis results suggest that a part of HCE consisting of the white smoke grenade disappeared and the other part was combined into $ZnCl_2$, $AlCl_3$, as a recycled intermediate product under closed system.

• 한국신뢰성학회:학술대회논문집
• /
• 한국신뢰성학회 2006년도 학술발표대회 논문집
• /
• pp.158-164
• /
• 2006

The creep behavior of newly developed composite geogrids which consists of PET yarns sheathed in PP were evaluated using SIM. For the SIM procedure, three test parameters, the applied loads, temperature steps and number of ribs were investigated, The study confirmed that temperature steps of 10 and 14$^{\circ}C$ up to 80$^{\circ}C$ are applicable for composite geogrids due to the different transition temperatures between two materials. At applied loads of 40 and 50%, only primary creep state was measured, while secondary creep state appeared at the applied loads of 60%, The lifetimes of composite geogrids were estimated at each of loading level using statistical reliability analysis technique. The results show that the lifetimes longer than 100 years can be predicted within 16 hours. Therefore, SIM is very effective and economical accelerated creep test methods, especially for lifetime prediction. This gives guidelines for users to select the appropriate factor of safety against creep considering the field condition within shorter test times.

• Korean Chemical Engineering Research
• /
• 제52권5호
• /
• pp.558-563
• /
• 2014

고분자 전해질 연료전지의 성능과 내구성에 미치는 막 전극 접합체(MEA) 제조방법의 영향에 대해 연구하기 위해 닥터 블레이드 방법, 스프레이 방법, 스크린 프린트 방법 그리고 스크린 프린트+스프레이 방법에 의해 MEA를 제조하였다. 제조된 MEA를 체결한 단위전지의 성능을 측정해 각 MEA의 초기 성능을 비교하였다. 10초간 0.6V 일정전압 유지 후 0.9 V에서 10초간 유지하는 전극 열화 가속 시험(AST)을 각 MEA 적용해 내구성을 시험하였다. 전극 열화 가속 시험 6,000 사이클 전 후 I-V 곡선, 임피던스, 순환 전압측정법(CV), 선형쓸음 전기량측정법(LSV), 투과전자현미경(TEM) 등을 측정하였다. 닥터 블레이드 방법에 의해 제조한 MEA의 초기 성능이 제일 높았고, 스크린 프린트+스프레이 방법에 의해 제조한 MEA가 제일 낮은 열화 속도를 보였다.