• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.5
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• pp.500-507
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• 2011

Acoustic emission(AE) signals during the polymerization shrinkage of composite resin subjected to the LED light exposure were detected through a wave guide method and a direct sensor attachment method. For PMMA, human tooth, stainless steel substrate, data of AE hits and amplitudes were compared. For the test using the wave guide, AE amplitudes decreased because of the attenuant wave. However, AE hits and 1st peak frequency distribution were not different according to the sensor attachments. Through the experiments, wave guide could be used for a nondestructive evaluation of the marginal disintegrative fracture of dental restoration.

• KSTLE International Journal
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• v.1 no.1
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• pp.29-33
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• 2000

In this study, a methodology is developed and confirmed to find the physical contact between the slider and disc due to the defects of disk during head seeking operation using acoustic emission (AE) signal. The head/disk contact was detected during random and standard seeks, whereas no contact was detected during track fellowing. During standard and random seeks, the torsion mode of slider excitation was observed at 680KHz. Therefore, it is thought that AE technique can be used as an alternative method of the glide test by monitoring existence of the torsional mode of the slider during seek operation or can be used to detect the spacing loss during seeking operation. By appropriately choosing the location of the sensor an order of magnitude increase in the sensitivity for RMS AE signal is observed. Therefore we can find take-off velocity clearly with high signal to noise ratio of AE signal.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.278-284
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• 1998

In order to measure the real contact force between head and disk on hard disk drive quantitatively, many technique of measurement have been developed. Acoustic Emission Sensor can be used for detect elastic energy of head/disk contact as arms value. In this study using pencil breaking test is proposed for finding contact force using transfer function between calibrated force and real contact force. And real AE data of subambient and tripad slider shows bending and torsional mode and their energy are dominant in hard disk and head contact.

• Tribology and Lubricants
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• v.15 no.4
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• pp.328-334
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• 1999

Acoustic emission (AE) sensor was used to evaluate the wear-life of CrN-coated steel disks with 1 $\mu\textrm{m}$ and 4 $\mu\textrm{m}$ coating thickness. The relationship between Af and friction signal from scratch test and sliding test was investigated. The first spatting of CrN film was detected by AR signals in the early stage of coating failures, and overall failures by friction signals. Therefore, the conservative design for coating-life should be done using the results of AE signals. Using the percent contact load, the ratio of sliding normal load to the critical scratch load and the number of cycles to failure was measured to predict the wear-life of CrN film. On the wear-life dia-gram the percent contact loads and the number of cycles to failure showed a good linear relationship on the log coordinate. As the load percentage was decreased, the diagram showed that the wear-limits, at which the coated steels survived more than 35,000 cycles, were about 4∼5% of the critical scratch loads.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.11
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• pp.163-170
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• 1997

End milling experiments are conducted to investigate characteristics of acoustic emission (AE) and cutting force singals due to tool fracture. The AE signals are obtained with a sensor attached to cutting fluid discharge nozzle. Tool states are identified with scanning electron microscopy and optical microscopy. It is demonstrated that the AE signals provide reliable informations about the cutting processes and tool states. Morever, tool fracture can be detected successfully using both the AE count rate and the standard deviation of principal cutting force.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.12
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• pp.2891-2898
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• 2000

The objective of this paper is to develop a fiber-optic acoustic emission(AE) sensor applicable to on-line monitoring systems which is suitable for long-distance signal transmission. An AE sensor was developed by use of a fiber-optic cantilever and an extrinsic Fabry-Perot interferometer(EEPI). The efficiency of signal processing was improved by driving the high frequency AE signals into the low frequency ones. In order to verify the developed sensor, the tensile and the pencil lead fracture(PLF) tests were performed including the experiment showing the Kaiser effect. Form tests, AE signals were successfully detected in the elastic-plastic deformation range, especially higher signals at the crack propagation. The developed sensor was expected to be used for an on-line monitoring of crack propagation in mechanical system.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1652-1654
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• 2002

The defects making partial discharge(PD) in a C-GIS(Cubicle Insulated Switchgear) initiate acoustic wave which can be detected using acoustic emission sensor placed outside or inside the C-GIS enclosure. In this paper, partial discharge property for 2 locations for AE sensor and 3 locations for defects in C-GIS are presented and PD waveforms were analyzed by PRPDA(Partial Resolved Partial Discharge Analysis). As a result, using post amplifier having gain of 10,000 and band pass filter having $20kHz{\sim}300kHz$, resolution of waveforms AE sensor signal by detected was good. Noise level was about 80 mV.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.359-360
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• 2008

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.337-337
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• 2008

Acoustic emission(AE) 센서의 감도개선을 위해 적합한 압전소자의 특성향상에 대해 연구하였다. AE 센서기술은 재료 내부에 마이크로크랙에 의해 변형과 손상이 생길 때 발생하는 기계적인 진동을 고감도 압전소자를 통해 전기적인 신호로 변환해 재료의 이상 유무를 알 수 있는 유용한 방법이다. AE 센서는 압전소자와 구리 캡 그리고 구리와 황동재질의 떨림판으로 구성되어 있다. 재료의 손상을 알기위한 변위가 낮을 경우 약한 AE 신호가 발생하며 검출하기가 어렵다. 미세변위에 의한 AE신호를 검출하기 위해서는 우수한 전기기계결합계수 (kp)와 압전상수($d_{33}$)를 갖는 압전소자가 필요하다. 이에 본 연구에서는 Pb$(Zr_{0.54}Ti_{0.46})O_3$ + x wt%$Cr_2O_3$ + y wt%$Nb_2O_5$ 조성에서 $Cr_2O_3$, $Nb_2O_5$ 첨가량 x, y 변화에 따른 압전특성과 AE센서특성을 고찰하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.921-924
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• 2004

This paper is to investigate a crack for plasma sprayed MCrAlY coated material by acoustic emission method in 4-point bending test. The CoNiCrAlY is coated on Inconel-718 by vacuum plasma spray process. Micro-hardness measurement was conducted by means of Micro Vickers-hardness indentor. The porosity of coating layer was measured using a SEM and Image Analyzer. AE monitoring system is composed of PICO type sensor, a wide band preamplifier(40dB), a PC and AE DSP(16/32 PAC) board. The AE count, Hit and energy of coating specimens is measured according to coating thickness.