• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.1667-1672
• /
• 2007

In order to assess the reliability of the exhaust bellows for automobiles, accelerated life test model and procedure are developed. By using this method, failure mechanism and life distribution are analyzed. The main results are as follows; i) the main failure mechanism is crack or breakage of inner flexible tube by shaken displacement at shear direction. ii) temperature is a second factor to affect a failure. iii) the life distribution of exhaust bellows is fitted well to Weibull life distribution and the shape parameter is 13.3 on condition of shaken displacement and $600^{\circ}C$

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.47-47
• /
• 2010

배전계통의 사고예방 기술은 전력수요 및 증설이 증가하고 있는 상황에서 시급히 확립되어야 한다. 특히 현장에서 시공되는 케이블은 시공과정의 관리가 쉽지 않을 뿐 아니라, 시공 중 발생될 수 있는 결함들을 검출하는 방법도 제한되어 있다. 본 연구에서는 국내에 도입된 진단방법을 통계적 방법으로 분석하고 효과적으로 점검할 수 있는 방법에 관한 검토하고자 한다.

• Proceedings of the KSME Conference
• /
• 2001.06a
• /
• pp.262-267
• /
• 2001

In this study, the Reliability of degraded steam turbine blade was evaluated using the limited fatigue data. The statistical estimation of limited fatigue data implies that some unknown uncertainties which may be involved in fatigue reliability analysis. Therefore, an appropriate distribution in the fatigue strength was determined by the characteristic distribution - linear correlation coefficient, fatigue physics, error parameter. 3-parameter Weibull distribution is the most appropriate distribution to assume for infinite region. The load applied on the blade is mainly tensile. The maximum Von-Mises stress is 219.4 MPa at the steady state service condition. The failure probability($F_p$) derived from the strength-stress interference model using Monte carlo simulation under variable service condition is 0.25% at the 99.99% confidence level.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.10
• /
• pp.1651-1658
• /
• 2001

It is necessary to evaluate fatigue strength and reliability of the connecting rod which is core part in automotive engine to assure the high level of durability of automobile. For this purpose, the loading conditions in automotive engine is obtained by the dynamic analysis. Based on these results, the critical section was identified by the finite element analysis. The fatigue strength under constant amplitude was evaluated and the mean of the fatigue limit at R = -2.27 derived from the staircase method was 311.2MPa. And the failure probability( F$\sub$p/ ) derived from the strength-stress interference model is 0.0003% at the 99.99% confidence level and the mean factor of safety was 4.2.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.8
• /
• pp.647-651
• /
• 2001

The dielectric breakdown of epoxy composites used for transformers was experimented and then its data were applied to Weibull distribution probability. First of all, speaking of dielectric breakdown properties, the more hardener increased, the stronger breakdown strength became at low temperature because of cross-linked density by the virtue of ester radical. The breakdown strength of specimens with filler was lower than it of non-filler specimens because it is believed that the adding filler forms interface and charge is accumulated in it, therefore the molecular motility is raised and the electric filed is concentrated. In the case of filled specimens with treating silane, the breakdown strength become much higher. Finally, from the analysis of weibull distribution, it was confirmed that to low allowed breakdown probability under 0,.1%, the applied field value needed to be under 21.5MV/cm.

• Journal of Korean Society on Water Environment
• /
• v.31 no.2
• /
• pp.142-150
• /
• 2015

The relationship between the number of benthic macroinvertebrate species and the accumulated survey area were investigated in a clean stream and an impaired stream of Korea. Five models to characterize species-area functions were compared, and the Weibull model fitted species-area data well. The other models (Arrhenius, Romell-Gleason, Kylin, Lognormal model) had small or notable bias. The maximum number of species and half-saturation area derived from the Weibull model may be used as the indicators of the carrying capacity and the habitat complexity respectively.

• Proceedings of the KIEE Conference
• /
• 2005.07c
• /
• pp.2043-2045
• /
• 2005

현재 점화코일은 소형화 및 친환경성을 위해 에폭시 몰딩 절연층으로 변화되었다. 그러나 에폭시 몰딩으로 변환됨에 따라 점화코일 내부 절연층에 대한 절연진단 및 노화에 대한 정확한 진단의 어려움으로 적절한 교체시기를 예측하기 더욱 어려워졌다. 그로 인해 점화장치부분에 대한 예기치 못한 사고는 대형사고 유발을 초래할 수 있다. 이에 본 논문에서는 비파괴검사의 일종인 부분방전을 이용한 열화검출을 연구하기 위해 열화에 따른 위상각-방전전하량-방전빈도수의 분포 특성을 조사하였다. 또한 방전 발생의 분포가 동일 조건에서도 매우 불규칙성을 가지고 있으므로 데이터의 정량화를 위해 불규칙적인 통계처리를 위한 와이블 분포를 사용하여 기기의 고장시간예측을 조사하였다.

• Proceedings of the KIEE Conference
• /
• 2004.11a
• /
• pp.264-267
• /
• 2004

The conventional testing as IEC-60587 is widely used in surface aging measurement of outside insulator those testing can carry out very short time in Lab testing. Also IEC-60587 testing is able to offer the standard judgement of relative degradation level of out side HV machine. Therefore it is very useful method compare to previous conventional tracking testing method and effective Lab testing method, But surface discharges(SD) have very complex characteristics of discharge pattern so it is required estimation research to development of precise analysis method. In recent, the study of IRR Camera is carrying out discover of temperature of power equipment through condition diagnosis and system development of degradation diagnosis.

• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.1
• /
• pp.61-67
• /
• 2000

Gears are the most commonly used parts in automotive and industrial applications. One of most common modes of gear failures is tooth breakage, which is usually produced by the bending fatigue failure. It is important to manufacture the gears which can withstand the applied stresses in view of safety and economic requirement. This paper deals with bending fatigue strength for cold forged bevel gear. Especially, to compare fatigue characteristics for manufacturing processes difference, bending fatigue tests of bevel gears made by three different processes respectively. Results indicate that the fatigue strength of bevel gear is improved by cold forging process. Intergranular fracture is found on fatigue fracture surface, and dimples are observed on final fracture surface. The fatigue failure cannot be considered as a deterministic quantity, but must be characterized statistically. This study proposes a method to estimate bending fatigue lift of the bevel gear using the probability-load-life and Weibull analysis.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.11a
• /
• pp.472-476
• /
• 2011

This paper presents the results of theoretical analysis and experimental test to verify the size effect on the fiber strength of filament wound pressure vessel. As a test method, a series of fully scaled hoop ring tests with filament wound carbon fiber-epoxy has been conducted. Test results showed remarkable size effect on fiber strength. And, as an analytical method, the WWLM(Weibull weakest link model) and SMFM(sequential multi-step failure model) were considered and compared to hoop ring test data. The analysis results showed significantly lower fiber strength value than that of test data. Through the modification of length size effect, modified SMFM is suggested. The fiber strengths from modified SMFM showed good agreement with test data.