• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.669-676
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• 2014

A three-way catalyst substrate for domestic passenger car satisfies the design criteria for exhaust gas exchange and pressure drop but does not have satisfactory thermal fatigue performance. Prefracture faults in this three-way catalyst substrate has often been discovered in vehicle repair or vehicle inspection facilities. This paper presents a thermal fatigue performance estimation method for a three-way catalyst substrate using a probabilistic strength reduction factor model. This method is superior to the thermal fatigue performance estimation method for a three-way catalyst substrate that uses a deterministic strength model.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.543-548
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• 2012

The use of glass applied to curved surface as a building material has increased in recent years. However, the curved glass is difficult to guarantee the quality in process of making it into double glazing, So it is vulnerable to thermal breakage. In this paper, when the glass broken during experiments, surface temperature difference on curved double glazing was compared to that of heat strengthened glass and flat glass. As a result, flat single glass was broken at temperature difference of 100~140 degrees but curved double glazing was broken at that of 40~60 degrees. Therefore, curved double glazing is more vulnerable than flat double glazing to thermal breakage, so it should be considered when applied to building facade.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.236-237
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• 2013

In recent years, the use of glass applied to curtain wall as a building facade material has increased in our nation. However, the non-tempered curved double glass is very easy to broke because it is difficult to guarantee the quality in process of making it into double glazing. So, it is more vulnerable to thermal breakage than tempered double glass. In this paper, surface temperature difference on curved double glazing was compared to that of heat strengthened glass and flat glass by conducting thermal breakage experiments. As a result, flat single glass was broken at temperature difference of 100~140 degrees but curved double glazing was broken at that of 40~60 degrees. Therefore, it was concluded that curved double glazing is more vulnerable than flat double glazing to thermal breakage, and it should be considered the possibility of thermal breakage when curtain wall glazing is applied as a building facade material.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.911-917
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• 2010

In this study, we performed structural and fatigue analyses of the engine exhaust manifold that was subjected to thermo-mechanical cyclic loading. The methodologies used in this study are based on an approach in which the techniques for modeling the exhaust system, the temperature-dependent properties of the material, and thermal cyclic loading are taken into consideration and a reliable strategy is adopted for failure prediction. An application example shows that at an elevated temperature, considerable compressive plastic deformation is observed and that at a low temperature, tensile stresses remain in those parts of the test exhaust manifold where failure is observed. In order to predict fatigue life, mechanical damage is determined on the basis of the stress.strain hysteresis loops by using the classical Coffin.Manson equation and by adopting a method in which the dissipated plastic energy is taken into consideration.

• Composites Research
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• v.16 no.1
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• pp.26-33
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• 2003

Utilizing a thermo-acoustic emission (AE) technique, a study on detection and evaluation of microfractures in cross-ply laminate composites was performed. Fiber breakages and matrix fractures formed by a cryogenic cooling at $-191^{\circ}C$ were observed with ultrasonic C-scan, optical and scanning electron microscopy. Those microfractures were monitored in a non-destructive in-situ state as three different types of thermo-AE signals classified on the basis of Fast-Fourier Transform and Short-Time Fourier Transform. Thus, it was concluded that real-time estimation of microfracture processes being formed during cryogenic cooling could be accomplished by monitoring such different types of thermo-AEs in each time-stage and then by analyzing thermo-AE behaviors for the respective AE types on the basis of the AE signal analysis results obtained during thermal heating and cooling load cycles.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.3
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• pp.261-268
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• 2001

An investigation on nondestructive evaluation of thermal stress-nduced damage in the composite laminates (3mm in thickness and $[+45_6/-45_6]_s$ lay-up angles) has been performed using the thermo-acoustic emission technique. Reduction of thermo-AE events due to repetitive thermal load cycles showed a Kaiser effect. An analysis of the thermo-AE behavior determined the stress free temperature of composite laminates. Fiber fracture and matrix cracks were observed using the optical microscopy, scanning electron microscopy and ultrasonic C-sean. Short-Time Fourier Transform of thermo-AE signals offered the time-frequency characteristics which might classily the thermo-AE as three different types to estimate the damage processes of the composites.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.2
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• pp.122-129
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• 2004

There is an increasing need for large flat panel display devices. PDP (Plasma Display Panel) is one of the most promising candidates for this need. Thermal shock failure of PDP glass during manufacturing process is a critical issue in PDP industry since it is closely related to the product yield and the production speed. In this study, thermal shock resistance of PDP glass is measured by water quenching test and an analysis scheme is described for estimating transient temperature and stress distributions during thermal shock. Based on the experimental data and the analysis results, a simple procedure for predicting the thermal shock failure of PDP glass is proposed. The fast cooling process for heated glass plates can accelerate the speed of PDP production, but often leads to thermal shock failure of the glass plates. Therefore, a design guideline for preventing the failure is presented from a viewpoint of high speed PDP manufacturing process. This design guideline can be used for PDP process design and thermal -shock failure prevention.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2000.06a
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• pp.1-6
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• 2000

가압 경수로의 증기발생기는 원자로(reactor vessel)와 가압기(pressurizer)에서 가열ㆍ가압된 1차 계통의 고온, 고압수가 터빈을 돌리는 2차 계통수와 열교환을 일으켜 고온ㆍ고압의 증기를 발생시키는 것으로, 전열관의 파손이 발생될 경우 1차 계통에서 2차 계통으로 방사능 물질이 누출되어 심각한 문제가 야기된다. 따라서 증기발생기의 전열관 손상이나 파손 문제는 원자력 발전소의 수명과 밀접한 관계가 있다. (중략)

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.76-78
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• 1993

간접적인 방법으로 가공중(In process)공구상태를 감시하기 위해, 센서신호를 분석하는 방법으로 시간영역 (Time Domain) 해석과 주파수 영역(Frequency Domain)해석이 주로 이용되어 왔다. 시간영역해석의 경우 RMS,PEak Value, 평균/분산을 이용한 정적분석과 AR 모델, ARMA 모델, Kalman Filter등 동적 시계열 모델이 연구되어 왔다. 주파수영역해석의 경우 푸리에 변환 (Fourier Transform)에 의한 신호해석 기술이 주로 이용되고 있다. 그러나 푸리에 변환된 결과에는 시간정보가 포함되어 있지 않고, 국부적인 변환결과가 전체를 대표하는 성질을 가지고 있다. 이에 비해 웨이브렛(Wavelet) 변환은 고주파성분에 대해서는 시간분해능이 높고, 저주파 성분에 대해서는 주파수분해능이 높은 다중해상도 해석기술로서 국소적인 변동점을 민검하게 검지하는 것이 가능하다. 본연구에서는 엔드밀 가공중 발생하는 공구의 파손을 검출하기 위해, 전류센서로 부터 얻은 이송축 부하 전류의 변화에 웨이브렛 변환을 통해 공구의 파손을 검출하는 방법에 대한 연구결과를 소개한다.

• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.391-393
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• 2011

본 연구에서는 원자력 발전 및 화력 발전소에서 Turbine 운전 시 열교환기 및 콘덴서에 증기를 응축시 열효율을 높여주기 위해 콘덴서 Tube 내에 이물질 및 스케일을 Sponge Ball을 이용하여 자동으로 제거하는 장치로서 콘덴서 튜브 클리닝 시스템(CTCS)에 사용되고 있는 Screen 재료인 Duplex Stainless Steel UNS S31803의 파손사례에 대해 연구하였다. 파손원인 분석은 스크린의 강도해석, 재료의 화학분석시험, 조직시험 및 점용접부의 신뢰성 시험(Peel-off test)으로 수행되었고 저항용접부의 용접 불량 때문에 발생하였을 확인하였다.