• 한국세라믹학회지
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• 제39권7호
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• pp.622-627
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• 2002

Multi-layer composites consisting of silicon nitride, silicon nitride-silicon carbide and boron nitride-alumina layers were prepared fly stacking the corresponding ceramic tapes. The composites demonstrated self-diagnostic capability and non-catastrophic failure behavior. The composites consisting of many thin layers exhibited high strength and stepwise increase of the electrical resistance during the flexure test. The strength of the composite with too thick silicon nitride layers was low and the electrical resistance was abruptly increased to the detection limit of the digital multi-meter during the test. An extensive crack branching was observed in the weak (BN + Al$_2$O$_3$)layer.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.30-35
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• 2002

This paper dealt with FMEA, which is a method of the analysis to secure safety and confidence coming up to customers'expectation in consideration of the environment of the corporation, the industrial environment, and the functional improvement. And by using FMEA, We showed the example analyzed the confidence of the Air Supply System. It was proved by the result of the analysis that the rate of the breakdown which is usually regarded as the first important point to reform can't satisfy the selecting basis to improve. Also the result said that it is not right to depend on only the rate of the failure in making the list of the reform. Through the analysis of the breakdown, FMEA can present the important factors of the reform to improve the confidence of the system. In this study would show the important factors of the improvement in order to product the goods guaranteed confidence through the method of FMEA.

• 연구논문집
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• 통권23호
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• pp.141-153
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• 1993

본 연구는 국내의 플랜지 전문생산업체에서 제작하여 국외의 정유회사로 공급한 플랜지중 1개가 수압시험중 균열이 발생되어, 이에 대한 원인규명을 하고자 하였다. 먼저 균열이 간 플랜지와 동일재질의 건전한 플랜지를 입수하여 화학성분분석, 기계적 성질, 개재물, 경도측정 및 미세조직관찰을 통하여 비교조사하였고 파괴플랜지 용접부의 조직 및 경도측정으로 용접부의 영향을 조사하였다. 또한 파괴면의 육안관찰, SEM, EPMA 및 XRD분석으로써 균열발생 시기와 상태등을 추정하였다.

• 연구논문집
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• 통권34호
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• pp.47-58
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• 2004

Power plants rely on air operated valves for the proper operation of many plant system. Many significant problems arise in vital systems of power plants due to air operated valve failures. This paper deals with the diagnosis technique and data acquisition method of an AOV actuator peformance. We constructed AOV diagnosis system and performed some tests to find out whether an AOV actuator was properly designed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.342.2-342
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• 2002

Fault tolerant control algorithm fer heteropolar magnetic bearings are presented. This fault tolerant control utilizes grouping of currents as C-cores in order to isolate magnetic fluxes. Hardware requirements to maintain fault tolerant control are reduced since decoupling chokes are not required in this control scheme. The currents supplied to each pole are redistributed, if some coils (ail suddenly, such that the resultant magnetic forces should remain invariant through coil failure events. (omitted)

• 연구논문집
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• 통권25호
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• pp.5-12
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• 1995

Mold platen are one of the most important structural components of the injection molding machine. Mold platen had been designed, and manufactured based on the experience and the method of trial and error. Recently, as the computer progress, the numerical simulation method using commercial finite element analysis code has been used to analyze the characteristics of components. It's a urgent problem to reduce the weight of mold platen while preserving the safety and reliability for the structual failure. Finite element analyses to establish basic design technologies and reducing the weight of mold platen were carried out. As result, we are obtained the about 10% reducing the weight for mold platen.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.190-197
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• 2004

In order to consider statistical properties of probability variables used in the structural analysis, the conventional approach using the safety factor based on past experience usually estimated the safety of a structure. Also, the real structures could only be analyzed with the error in estimation of loads, material characters and the dimensions of the members. But the errors should be considered systematically in the structural analysis. In this paper, we estimated the probability of failure of the pressure vessel. And also, this paper presents sensitivity values of the random variable. Finally, we show that reliability index and probability of failure can present the tolerance limit of dimension of randam variables.

• 한국신뢰성학회지:신뢰성응용연구
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• 제14권1호
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• pp.71-80
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• 2014

In the mechanical design process various types of errors are bound to occur. In order to prevent such mechanical malfunctions and decrease number of instances of errors, various technique are utilized. The purpose of this research is to demonstrate the effectiveness of the combined service Blueprint and FMEA (Failure Mode and Effect Analysis) by applying such method to machine process. The results are as follows: First, modification can be obtained by discovering the failure mode hidden within the inner side of the blueprint. Second, issues within the company are found when conducting the machine design process that is not visible from the outside. Therefore, potential errors can be effectively resolved by preventing failure mode in advance and eventually high quality of the product could be obtained as well as its reliability.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.281-286
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• 2001

Tilting pad journal bearings have been widely used in a high speed rotating machinery, such as steam turbines and gas turbines, owing to their inherent stability characteristics. However, some peculiar fatigue failure in the babbitt metal due to spragging has been continuously occurred at the leading edge of the upper pads. The spragging is defined as the pad vibration initiated on the upper unloaded pads in a tilting pad journal bearing. This paper describes both several kinds of bearing failure related with spragging and the theoretical investigation on the prevention of the spragging phenomenon using the variation of preload. Results show that positive preload(m>0.5) assures all pads remain statically loaded under all operating conditions. For the change of design parameter to prevent spragging, thermo-hydrodynamic lubrication and rotor dynamic analysis were performed to verify temperature limitation on bearing and vibration problems on rotor bearing system.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권1호
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• pp.78-82
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• 2017

Purpose: The purpose of this study is to evaluate failure characteristic and mechanism of four commercial water-repellent coatings for elevated temperature machinery applications. Method: Thermal degradation was performed for up to 64 thermal cycles. 1 cycle consists of 15 minute holding at 523K under 300rpm revolution and 15 minute-natural cooling. Contact angle was measured and microstructure of the coating layer was observed by using a scanning electron microscope. Results: Four kinds of commercial repellent coating showed hydrophobic or super-hydrophobic property implying that all coatings are suitable for room temperature application. Contact angle of three kinds of commercial coatings decreased rapidly after thermal exposure, while only one specimen having hydrophobic surface showed extremely slow degradation. Conclusion: Observed decrease in contact angle of the coatings were attributed to formation of macro-sized pores and disappearance of micro-protrusion during thermal exposure. Optimum water-repellent coating needs to be selected under the consideration of initial contact angle as sell as service temperature.