• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.43-48
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• 2008

Gear system has been widely used in industrial applications and unexpected failures of gears are not only extremely damaging but also lead to economic losses. So, early detection of fault is important for diagnosis machine condition. And acoustic emission is an efficient non destructive testing technique for the diagnosis of machine health and is useful technique for early detection of fault because it can find low-amplitude and high-frequency signal on account of high sensibility. Therefore, in this paper, the AE signal was measured and preprocessed using envelop analysis for gearbox with misalignment between pinion and gear. And then the vibration characteristic of gear misalignment was analyzed.

• Agricultural and Biosystems Engineering
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• 제2권2호
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• pp.75-80
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• 2001

This paper describes method to diagnose abiotic stresses such ad low root temperature, low light intensity and high salinity in cucumber plants with several physiological instruments. The stresses could be detected by measuring and analyzing the differences in chlorophyll content, temperature difference between leaf and atmosphere and light absorptance at wavelengths of 480, 560, 710, 1420 and 1650nm. It was concluded that the stresses could be first diagnosed from the 3rd to 10th day after treatment and the overall accuracy of diagnosis was estimated between 25 and 75%. near-infrared spectrometer showed better and earlier detection than the other instruments investigated.

• 비파괴검사학회지
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• 제32권3호
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• pp.291-295
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• 2012

In the industrial field, real-time monitoring system like a fault early detection is very important. For this, the infrared thermography technique as a new diagnosis method is proposed. This study is focused on the damage detection and temperature characteristic analysis of ball bearing using the non-destructive infrared thermography method. In this paper, thermal image and temperature data were measured by a Cedip Silver 450 M infrared camera. Based on the results, the temperature characteristics under the conditions of normal, loss lubrication, damage, dynamic loading, and damage under loading were analyzed. It was confirmed that the infrared technique is very useful for the detection of the bearing damage.

• Agricultural and Biosystems Engineering
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• 제2권1호
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• pp.1-6
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• 2001

This paper represents methods to diagnose nutrient deficient stresses of cucumber plants using several physiological instruments. The stresses could be detected by measuring and analyzing the difference of chlorophyll content, photochemical efficiency (Fv/Fm), temperature difference (DT) and light absorbance at wavelengths of 480nm, 560nm and 710nm between deficient and control plants. From the all over experiments, the stresses could be first diagnosed in the 3rd to 5th day in general after treatment and the overall diagnosis rate was estimated at more than 50% up to 100%.

• 한국소음진동공학회논문집
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• 제18권12호
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• pp.1243-1249
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• 2008

Gear system has been widely used in industrial applications and unexpected failures of gears are not only extremely damaging but also leading to economic losses. So, early detection of fault is important for diagnosis machine condition. And acoustic emission is an efficient non-destructive testing technique fur the diagnosis of machine health and is useful technique far early detection of fault because it can find low-amplitude and high-frequency signal on account of high sensibility. Therefore, in this paper, the AE signal was measured and preprocessed using envelope analysis for gearbox with misalignment between pinion and gear. And then the gear misalignment's vibration characteristic were analyzed.

• Transactions on Electrical and Electronic Materials
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• 제18권6호
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• pp.338-340
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• 2017

Breakdown of solid insulating materials in power equipment could result in undesired outages and replacements, and may be due to an increase in electric stress on the material. Therefore, it is necessary to conduct a proper diagnosis of materials before their practical use. In this work, a few inherent properties of different non-cellulosic insulating materials, such as Nomex, Teflon, laminated Nomex, glass bonded mica, epoxy resin bonded mica paper, and epoxy resin bonded fiberglass, have been evaluated by performing non-destructive dielectric diagnostic measurements, and an attempt has been made to correlate these basic parameters to evaluate the breakdown strength (BDS). An equation has been proposed using a basic theory which defines the correlation between the BDS, dielectric constant, dissipation factor, sample thickness, and volume resistivity. The results obtained from the equation are also compared with the experimental values. The suggested equation will be helpful to predict the BDS of any non-cellulosic material without experimentation in the laboratory.

• 비파괴검사학회지
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• 제31권2호
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• pp.134-138
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• 2011

회전기기의 고장 탐지에 있어 기존의 진단법과 달리 동적 하중조건 하에서 비접촉, 비파괴의 적외선 열화상 기법이 제안된다. 본 논문에서는 단열 깊은 홈 볼 베어링을 시편으로 하여, 회전기기의 기존의 고장 진단법 대신 수동형 열화상 기법을 이용한 시험을 수행하였다. 추가적으로, 제안된 방법의 효율성을 평가하기 위해 기존의 진동 스펙트럼 분석법을 적용하여 열화상 시험법을 비교하였다. 시혐의 결과로써, 동적 하중조건 하 볼 베어령의 온도분포 특성이 철저히 분석되었다.

• Smart Structures and Systems
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• 제19권2호
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• pp.195-202
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• 2017

The aim of this paper is to develop a novel method to determine the severity of a damage in a thin plate. This paper presents a novel fault detection and diagnosis approach employing a new electromagnetic acoustic transducer, called EMAT, together with a complex signal processing method. The method consists in the recognition of a fault that exists within the structure, the fault location, i.e. the identification of the geometric position of damage, and the determining the significance of the damage, which indicates the importance or severity of the defect. The main scientific novelties presented in this paper is: to develop of a new type of electromagnetic acoustic transducer; to incorporate wavelet transforms for signal representation enhancements; to investigate multi-parametric analysis for noise identification and defect classification; to study attenuation curves properties for defect localization improvement; flaw sizing and location algorithm development.

• 비파괴검사학회지
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• 제22권3호
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• pp.254-260
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• 2002

화력발전소 보일러 튜브 및 대형 유체수송관의 자동 진단을 위해 비파괴검사 방법을 사용하는 두 가지 형태의 이동로봇을 개발하였다. 개발된 이동로봇은 보일러 튜브 또는 유체수송관의 외면을 주행하면서 전자기 초음파 탐촉자를 이용하여 파이프 벽면에 발생하는 미세한 구멍, 균열 또는 부식 및 침식에 의한 감육 등과 같은 결함을 검출한다. 이와 같은 이동로봇을 이용한 결합 검출의 자동화는 열악한 환경에서 작업자의 위험 없이 대형 구조물의 중대한 결함을 방지하는 유용한 수단으로 활용될 수 있다.

• 한국정밀공학회지
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• 제21권5호
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• pp.73-82
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• 2004

This paper presents the study on damage diagnosis of an intelligent cantilevered beams using PZT actuator and PVDF sensor This study provides the theoretical and experimental verification to examine structural damage. Time domain analysis for the non-destructive detection of damage is presented by parameterized partial differential equations and Galerkin approximation techniques. The time histories of the vibration response of structure were used to identify the presence of damage. Furthermore, this systematic approach permits one to use the piezomaterials to both excite and sense the vibration of structures. We also carried out the experimental verification about reliability of theoretical methods fur detecting the damage of a composite beam with PZT actuator and PVDF sensor. Experimental results are presented from tests on cantilevered composite beams which is damaged at different location and different dimensions. The results were compared with the simulation results. Good agreement between the results was found for the time shifts and amplitude difference in transients response of the cantilevered beam.