• 한국정밀공학회지
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• 제12권3호
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• pp.130-143
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• 1995

This paper presents a new methodology for on-line tool breadage detection by sensor fusion of an acoustic emission (AE) sensor and a built-in force sensor. A built-in piezoelectric force sensor, instead of a tool dynamometer, was used to measure the cutting force without altering the machine tool dynamics. The sensor was inserted in the tool turret housing of an NC lathe. FEM analysis was carried out to locate the most sensitive position for the sensor. A burst of AE signal was used as a triggering signal to inspect the cutting force. A sighificant drop of cutting force was utilized to detect tool breakage. The algorithm was implemented on a DSP board for in-process tool breakage detection. Experiental works showed an excellent monitoring capability of the proposed tool breakage detection system.

• 비파괴검사학회지
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• 제27권1호
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• pp.1-7
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• 2007

섬유강화 복합재료가 항공기, 우주 구조물, 로봇 팔 등에 널리 사용됨에 따라 복합재료의 신뢰도와 안전성을 향상시키기 위하여 이에 대한 비파괴검사법은 매우 중요한 연구분야로 대두되고 있다. AE법은 복합재의 균열, 섬유 또는 수지재의 파손, 층간분리 등의 발생 및 성장과정에서 발생되는 탄성파로 인한 스트레인 에너지를 검출하는 방법이다. 본 논문에서는 $8{\times}8$ 매트릭스형 피에조 센서를 사용하여 인장시험 하에서 발생되는 AE신호를 측정하고 분석하였다. 이를 위하여 AE신호의 전달거리를 제어할 수 있는 전용회로를 설계하고 제작하였다. 또한 64채널의 AE신호를 획득하기 위하여 발광다이오드를 사용한 광학 저장장치를 구성하였다. 실험결과, $8{\times}8$ 매트릭스형 피에조 센서를 이용하여 복합재료에서 발생되는 AE신호의 발생지점과 전파경로를 효과적으로 검출할 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.330-333
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• 2006

In this paper experimental tests were performed to evaluate velocities of the acoustic waves through prestressed concrete beam and source locations using AE technique. Seven AE sensors are mounted on the surface of 5m length test beam with equal spacing and using Schmidt Hammer AE events are made 18 locations. The velocities of AE signals are evaluated using the time differences of arrival times and the distances between the AE source loactions and the AE sensor locations. In addition, using the Least Square Method, the AE source locations are re-evaluated reversely using both of the arrival times and the velocities of AE signals. Test results show the average velocity of the AE signals is about 4,000m/sec and the velocity decreased with the increase of the trevalling times due to the effect of attenuation. Based on the estimation of the source locations, it is observed that the accuracy of source location is increased when the velocity of each AE sensor used rather than the average velocity.

• 한국전기전자재료학회논문지
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• 제27권11호
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• pp.696-701
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• 2014

In this study, in order to develop coupled vibration mode piezoelectric devices for Acoustic Emission (abbreviated as AE) sensor application with outstanding displacement and piezoelectric properties have been simulated by ATILA FEM program. And, From the results of ATILA simulation, the AE sensor specimen, obtained superior electromechanical coupling factor and displacement, when the size of specimen is $3.45mm{\Phi}{\times}3.45mm$ with ratio of diameter/thickness(${\Phi}/T$)= 1.0. Therefore, AE sensor was fabricated by (Na,K,Li)(Nb,Ta) $O_3$(abbreviated as NKL-NT) system piezoelectric ceramics using coupled vibration mode. The piezoelectric properties of NKL-NT ceramics was exhibited that piezoelectric constant($d_{33}$), piezoelectric voltage constant($g_{33}$) and electro mechanical coupling factor($k_p$) have the excellent values of 261[pC/N], 40.10[$10^{-3}Vm/N$], and 0.44, respectively. The manufactured piezoelectric device with ratio of ${\Phi}/T$= 1.0 indicated the optimum values of resonant frequency(fr)= 556.5[kHz], antiresonant frequency(fa)=631.1[kHz], and effective electromechanical coupling factor(keff)= 0.473. The maximum sensitivity of the coupled vibration mode AE sensor was 55[dB] at the resonant frequency of 75[kHz]. The results show that the coupled vibration mode piezoelectric device is a promising candidate for the application AE sensor piezoelectric device.

• 대한기계학회논문집A
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• 제24권12호
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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.

• 대한기계학회논문집A
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• 제33권5호
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• pp.514-520
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• 2009

In configuring an automated polishing system, a monitoring scheme to estimate the surface roughness is necessary. In this study, a precision polishing process, magnetic abrasive finishing (MAF), along with an in-process monitoring setup was investigated. A magnetic tooling is connected to a CNC machining to polish the surface of stavax(S136) die steel workpieces. During finishing experiments, both AE signals and force signals were sampled and analysed. The finishing results show that MAF has nano scale finishing capability (upto 8nm in surface roughness) and the sensor signals have strong correlations with the parameters such as gap between the tool and workpiece, feed rate and abrasive size. In addition, the signals were utilized as the input parameters of artificial neural networks to predict generated surface roughness. Among the three networks constructed -AE rms input, force input, AE+force input- the ANN with sensor fusion (AE+force) produced most stable results. From above, it has been shown that the proposed sensor fusion scheme is appropriate for the monitoring and prediction of the nano scale precision finishing process.

• 한국전기전자재료학회논문지
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• 제26권2호
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• pp.114-118
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• 2013

In this study, coupled mode piezoelectric devices for AE sensor application with excellent displacement and piezoelectric characteristics were simulated using ATILA FEM program, and then fabricated. Displacements and electromechanical coupling factors of the piezoelectric devices were investigated. The simulation results showed that excellent displacement and electromechanical coupling factor were obtained when the ratio of diameter/thickness was 1.0. The piezoelectric device of ${\Phi}/T$= 1.0 exhibited the optimum values of fr= 406 kHz, displacement= $6.11{\times}10^{-8}[m]$, $k_{eff}$= 0.648. The results show that the coupled vibration mode piezoelectric device is a promising candidate for the application of AE sensor piezoelectric device.

• 대한기계학회논문집A
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• 제38권8호
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• pp.863-867
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• 2014

본 연구에서는 화학 기계 연마(CMP) 공정 중 발생하는 다양한 영역대의 신호를 분석하기 위하여 음향 방출 센서(AE)를 이용하였다. 특히 음향 방출 센서는 공정 중 발생하는 기계적 소음을 전기적 신호로 변환하기 용이하며, 특히 고주파 영역대의 신호를 감지하기에 용이하다. 그래서 본 연구에서는 CMP 장비에 음향 방출 센서를 부착하여 CMP 공정 중 발생하는 신호를 동시에 획득하였다. 본 음향 방출 모니터링 시스템은 CMP 공정 조건 변화 및 패드, 슬러리, 웨이퍼와 같은 소모재의 변화에 따른 신호분석을 하기 위해 제작 되었다. 본 연구에서는 산화막 웨이퍼와 구리막 웨이퍼에 본 시스템을 적용하였다. 음향 방출 센서로 획득한 신호로 Raw 신호 분석, 주파수 분석, 진폭 분석을 통해서 CMP 공정중 발생하는 현상을 분석하였다. 최종적으로 다양한 대역폭의 신호를 음향 방출 센서로 획득하여 CMP 공정 모니터링이 가능함을 확인하고자 하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권1호
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• pp.44-51
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• 2000

In this paper, using a wide-band AE sensor with the frequency range from 100[kHz] to 1.5[kHz], the frequency spectra of AE signals generated from the corona discharges of the needle-plane gap and from the partial discharges of an epoxy void were analyzed to determine the proper ultrasonic sensor with optimum frequency range according to the patterns of corona discharges. We also examined the propagation characteristics of AE signals in oil and the relationship between the magnitude of corona discharge and the magnitude of AE signals in peak-to-peak value under the application of 60[Hz] ac high-voltage. From these results, the main frequency spectra of AE signals emitted from the corona discharges of the needle-plane gap were about 130[kHz] by the fast fourier transform, but the main frequency spectra appeared to be 230[kHz] in the partial discharges of an epoxy void. The magnitude of AE signals was proportional to the magnitude of corona discharge and discharge current pulse with increasing the applied voltages.

• 한국전기전자재료학회논문지
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• 제20권3호
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• pp.218-222
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• 2007

In this study, Acoustic emission(AE) sensors were fabricated using lead-free piezoelectric ceramics for prohibiting environmental pollution. Structure of AE sensors were designed as Langvin type air backing form. Here, the piezoelectic element was used as PZT(EC-65)(AE1) and NKN(AE2), respectively. The measured resonant frequency, the maximum sensitivity frequency and sensitivity of AE sensors were as follows ; 143 kHz, 29.4 kHz and 69.3 dB in AE1 and 179 kHz, 29.4 kHz and 66.3dB in AE2, respectively.