• Tribology and Lubricants
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• 제17권1호
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• pp.1-9
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• 2001

Hard disk drives operate in various environmental conditions. Thus, it is necessary to assess the reliability of the head/disk interface under these conditions. In this work, stiction and acoustic emission signals were investigated under different temperature, humidity, and ambient pressure conditions. Also, track average amplitude was observed for disk failure in N$_2$environment. It is shown that failure of the head/disk interface occurs more readily at high temperature and low ambient pressure conditions.

• 한국안전학회지
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• 제16권4호
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• pp.7-13
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• 2001

Wire electrical discharge machining experiments in conducted to investigate characteristics of acoustic emission (AE) and electrical discharge energy due to current peak (I$_{p}$), pulse on time($\tau$/on/). The AE signals are obtained with a sensor attached to workpiece side. Machining states are identified with scanning electron microscopy and residual stress analyzer. It is demonstrated that the residual stress provide reliable informations about the machining states. Moreover, machining states can be detected successfully using both the residual stress and AE count rate.e.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.243-247
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• 2001

As a means to reduce stiction in the landing zone padded sliders can be used. In this work the performance of padded slider was investigated using a commercial spin stand. The friction and acoustic emission signals were measured during the experiment. It is shown that padded slider show superior friction and AE characteristics. However, the wear properties of the pads should be further Improved.

• 비파괴검사학회지
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• 제25권4호
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• pp.274-286
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• 2005

본 연구에서는 편측노치를 갖는 단일 hi판 및 유리섬유/알루미늄 혼합 적층판에 대해 인장하중하의 파괴거동에 따른 음향방출(AE) 특성을 살펴보았다. 단일 알루미늄의 파괴시에 발생하는 AE신호는 저주파수 대역을 갖는 신호와 고주파수 대역을 갖는 신호의 2가지 형태로 분류될 수 있었다. 고주파수 대역의 AE는 0.45mm 변위 보다 큰 후반부 하중단계에서 주로 검출되었다. 유리섬유/알루미늄 혼합 적층판의 경우에는, 고진폭의 긴 유지시간의 신호가 FFT 주파수 해석에 의거하여 거시적인 균열진전이나 A1층과 섬유층 사이의 층간분리에 해당하는 신호로 추정되었다. 위와 같은 AE신호의 해석결과와 광학현미경 및 초음파 스캔에 의한 파괴관찰에 의거하여 섬유층 배향에 따라 상이한 섬유/알루미늄 적층판의 파괴거동과 관련된 AE특성을 규명하였다.

• 한국컴퓨터정보학회논문지
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• 제19권11호
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• pp.17-24
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• 2014

본 논문에서는 저속으로 회전하는 유도 전동기의 베어링 결함을 검출하기 위해 음향 방출 신호와 히스토그램 모델링을 이용하는 방법을 제안한다. 제안한 방법은 정규화된 결함 신호가 구성하는 히스토그램의 포락선을 모델링하여, 부분 상관 계수와 DET(Distance Evaluation Technique) 기법을 이용하여 결함 유형별 고유한 특징을 추출 및 선택한다. 추출된 특징을 SVR(Support Vector Regression) 분류기의 입력으로 사용하여 베어링의 내륜, 외륜 및 롤러 결함을 분류한다. 최적의 분류 성능을 위해 SVR 커널함수의 매개변수를 0.01에서 1.0까지 변화시키고, 특징 개수는 2에서 150까지 변화시키면서 실험한 결과, 0.64-0.65의 매개변수와 75개의 특징 개수에서 제안한 방법은 약 91%의 분류 성능을 보였고, 또한 기존의 결함 분류 알고리즘보다 높은 분류 성능을 보였다.

• Journal of Mechanical Science and Technology
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• 제17권3호
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• pp.391-399
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• 2003

The thermo-acoustic emission (AE) technique has been applied for nondestructive characterization of composite laminates subjected to cryogenic cooling. Thermo-AE events during heating and cooling cycles showed a Kaiser effect. An analysis of the thermo-AE behavior obtained during the 1st heating period suggested a method for determining the stress-free temperature of the composite laminates. Three different thermo-AE types classified by a short-time Fourier transform of AE signals enabled to offer a nondestructive estimation of the cryogenic damages of the composites, in that the different thermo-AE types corresponded to secondary microfracturing in the matrix contacting between crack surfaces and some abrasive contact between broken fiber ends during thermal load cycles.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.273-274
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• 2002

In order to evaluate the flying characteristics of slider, the acoustic emission (AE) as well as friction signals are typically utilized. In this work the frequency spectrum analysis is performed using the AE signal obtained during the head/disk interaction such as load/unload mechanism using ramp, impact situation in the presence of a bump on disk surface and other contact phenomena including particle interaction. It was shown that the influence of impact can be characterized effectively in the AE frequency spectrum. As a result of this work, frequency spectrum analysis will be utilized with better understanding for studying the head/disk interface (HDI) characteristics and monitoring the particle interaction in HDI effectively.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.191-192
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• 2002

The scuffing failure is a critical problem in modern machine components, especially for the requirement of high efficiency and small size. In this study. scuffing experiments are conducted using Acoustic Emission(AE) measurement by an indirect sensing approach to detect scuffing failure. Using AE signals we con get and indication about the state of the friction processes, about the quality of solid and liquid layers on the contacting surface in real time. The FFT(Fast Fourier Transform)analyses of the AE signal are used to understand the interfacial interaction and the relationship between the AE signal and the state of contact is presented.

• 한국정밀공학회지
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• 제22권4호
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• pp.60-67
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• 2005

Compared with conventional welding, laser spot welding offers a unique combination of high speed, precision and low heat distortion. This combination of advantages is attractive for manufacturing industries including automotive and electronics companies. In this paper, a real time monitoring scheme fur a pulsed Nd:YAG laser spot welding was suggested. Acoustic emission (AE) signals were collected during welding and analyzed for given process conditions such as laser power and pulse duration. A back propagation artificial neural network, with AE frequency content inputs, was used to predict the weldability of stainless steel sheets.

• 동력기계공학회지
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• 제4권2호
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• pp.52-57
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• 2000

We investigated the fatigue crack propagation of base metal, weld metal and heat attected zone in 316L stainless steel. And we analysed acoustic emission signals during the fatigue test by time-frequency analysis method. The specimens of weld metal and HAZ had longer fatigue life and slower rate of crack propagation better than base metal. And as a result of time-frequency was 200-300 kHz was obtained by fatigue crack propagation and 500 kHz was obtained by dimple and separate of inclusion.