• 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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.603-604
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• 2012

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.359-360
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• 2008

• 한국소음진동공학회논문집
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• 제20권5호
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• pp.437-443
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• 2010

SAW device is widely used as band pass filters, chemical or physical sensors, and actuators. In this paper, we propose the capacitive gap measurement system with high precision using SAW device. The research process is mainly composed of theoretical and experimental part. In the theoretical part, equivalent circuit model was used to predict the SAW response by the change of load impedance. In the experimental part, commercialized capacitor was used to see the SAW response by the change of load capacitance to check the feasibility as a sensor unit. After that, experimental setup to measure and adjust the gap was made and the SAW response by the change of gap which caused the capacitance change was measured. Finally, resolution and stroke was decided compared with the signal change and basic measurement noise level.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 추계학술대회 논문집
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• pp.537-537
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• 2010

High precision sensing is very important in various technologies. Especially, it is more important when it were applied to nano/micro meter level's sensing like AFM, storage, etc. And capacitive sensing is widely used method. To improve the measurement efficiency, many signal conditioners were studied and one of them was surface acoustic wave (SAW) device. SAW device is very widely used as a high frequency bandwidth filter. Due to the reflective characteristic of high frequency, the response of SAW device contains both propagative and reflective signal at the external impedance. In this paper, we used SAW device as signal conditioner of capacitive sensor. And high precision gap measurement was executed using capacitive load. Reference signal was reflective SAW response and the magnitude at the center frequency of SAW device by the change of impedance was checked. Finally, the attainable gap resolution was determined.

• 대한기계학회논문집A
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• 제23권6호
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• pp.1011-1017
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• 1999

Electrolytic in-process dressing grinding technique which enables application of metal bond wheels with fine superabrasives in mirror surface grinding operations has developed. It is possible to make efficient precision machining of hard and brittle material such as ceramic and hard metal by the employment of this technique. However, in order to ensure the success of performances such as efficient machining, surface finish, and surface quality, it is important to sustain the insulating layer that has sharply exposed abrasives in wheel surface. Using AE(Acoustic Emission) sensor, this paper will show whether the insulating layer sustains stably or not in real grinding time. And by comparing AErms value and surface roughness their thresholds for stable electrolytic in-process dressing grinding will be determined.

• 한국음향학회지
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• 제19권2호
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• pp.8-12
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• 2000

본 논문은 주위 환경인 수압 및 수온변화에 따른 맨드릴형 광-음향센서의 감도특성을 분석한 것에 관한 것이다. 음향감지부의 구조로는 실린더형, 중공 층상복합체형 및 air cavity가 삽입된 중공 층상복합체를 선정하고, 주위 수압과 수온변화에 따른 광-음향센서의 감도특성을 분석하였다. 맨드릴형 광-음향센서는 주위 정수압의 변화에 대해 0.15dB 미만의 음향감도 변화를 나타내고, 수압변화에 대해 안정적인 특성을 보유하고 있다. 주위 수온변화에 대한 음향감도의 상대적인 안정성은 air cavity가 삽입된 중공 나일론 층상복합체를 이용한 맨드릴형 광-음향센서가 가장 우수한 것으로 나타났다.

• 비파괴검사학회지
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• 제31권5호
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• pp.500-507
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• 2011

본 연구에서는 치아 시편에 AE 센서를 직접 부착하는 방법과 웨이브 가이드(waveguide)를 사용하는 방법을 이용하여 치아에 충전된 치과용 복합레진의 광중합 수축에 따른 AE 신호를 검출하여 해석하였다. PMMA, 스테인리스 스틸, 인간 치아 시편을 사용하여 AE hit와 AE 진폭(amplitude) 거동을 비교하였다. 웨이브 가이드를 사용한 경우 전파 중에 발생하는 반사파에 의한 파형의 변형으로 진폭 및 hit 수의 감소가 나타났으나, 시편의 재질에 따른 신호의 발생빈도와 1차 중심주파수의 대역은 웨이브 가이드 사용 여부에 따라 차이가 없었다.

• Smart Structures and Systems
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• 제18권3호
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• pp.471-484
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• 2016

Optical fiber sensors have been proven that they have the potential to detect high-frequency ultrasonic signals, in structural health monitoring field which generally refers to acoustic emission signals from active structural damages and guided waves excited by ultrasonic actuators and propagating in waveguide. In this work, the sensing properties of optical fiber sensors based on Mach-Zehnder interferometer were investigated in the metal plate. Analytical formulas were conducted first to explore the parameters affecting its sensing performances. Due to the simple and definable frequency component, the Lamb wave excited by the piezoelectric wafer was employed to study the sensitivity of the proposed optical fiber sensors with respect to the frequency, rather than the acoustic emission signals. In the experiments, according to above investigations, spiral shape optical fiber sensors with different size were selected to increase their sensitivity. Lamb waves were excited by a circular piezoelectric wafer, while another piezoelectric wafer was used to compare their voltage responses. Furthermore, by changing the excitation frequency, the tuning frequency characteristic of the proposed optical fiber sensor was also investigated experimentally.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.169-174
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• 2006

The outstanding mechanical property of optical fiber and the merits of acoustic emission sensing technique are unified for novel sensor system. The generated ultrasonic wave from piezoelectric generator are propagated along the optical fiber and also sensed. The propagated wave can be influence by external pressure on the optical fiber or environmental circumstance. The optical fiber sensor using ultrasonic wave has advantages compare with existing sensor system. In this study, the sensitivity of the optical fiber sensor is experimentally investigated. As the applications of the optical fiber sensor system using piezoelectric ultrasonic waves, the point load on the optical fiber is measured and the monitoring system for the void fraction of two phase flows is developed. The experimental results show the linear relationship between sensed voltage and void fraction.