• Journal of Sensor Science and Technology
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• v.8 no.6
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• pp.469-475
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• 1999

The chips may be produced in the form of either broken chips or unbroken chips in turning process. The unbroken chips are dangerous to the operator and difficult to handle at high speed machining. The signal of Acoustic Emission is related to cutting conditions, tool materials, test conditions and tool geometry in turning. The relationship between AE signal and chip formation was experimentally investigated. The experimental results show that two types of chip formations are possible to classify from the statistical analysis of the amplitude of AE signal. The AE-sensor could be used to monitor the chip condition in turning.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.917-925
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• 2006

Experimental tests were performed to estimate velocities of the acoustic signals through prestressed concrete beam and source locations using acoustic emission (AE) techniques. Seven AE sensors are mounted on the surface of 5m length test beam with equal spacing and using Schmidt Hammer AE events are made at 18 locations. The velocities of AE signals are estimated using the time differences of arrival times and the distances between the source locations 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 4,000 m/sec and the velocity decreased with the increase of the distance from source locations to AE sensors due to the effect of attenuation. Based on the estimation of the source locations, it is observed that the errors of source locations are decreased when the velocities of each AE sensor are used rather than the average velocity.

• 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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.863-867
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• 2014

In this study, an acoustic emission (AE) sensor was used for measuring the abrasive and molecular-scale phenomena in chemical mechanical polishing (CMP). An AE sensor is a transducer that converts a mechanical wave into an electrical signal, and is capable of acquiring high-level frequencies from materials. Therefore, an AE sensor was installed in the CMP equipment and the signals were measured simultaneously during the polishing process. In this study, an AE monitoring system was developed for investigating the sensitivity of the AE signal to (a) the variations in the material properties of the pad, slurry, and wafer and (b) the change in conditions during the CMP process. This system was adapted to Oxide and Cu CMP processes. AE signal parameters including AE raw frequency, FFT, and amplitude were analyzed for understanding the abrasive and molecular-level phenomena in the CMP process. Finally, we verified that AE sensors with different bandwidths could function in complementary ways during CMP process monitoring.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.10a
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• pp.239-243
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• 2001

본 연구에서는 절삭중 공구파손을 실시간으로 검출할 수있는 시스템을 구성하기 위한 일환으로 일차로 AE(acoustic emission)센서를 사용하여 mechanism의 특성과 공구파손에 따른 주파수 특성을 해석했고, 차후 연구로서 AE센서가 아닌 가속도센서와 전류센서 및 공작기계의 절삭동력계를 이용한 복합계측시 스템을 구성하여 절삭특성 및 공구파손이 발생할 때의 신호특성을 해석했다.

• Composites Research
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• v.24 no.6
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• pp.49-55
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• 2011

The use of advanced composite materials in main structures of military and civil aircraft has been increased rapidly because of their considerable metals in high specific strength and stiffness. However, the mechanical properties of composite materials may severely degrade in the presence of damage. Especially, the high-velocity impact such as a hailstorm, and a small piece of tire or stone during high taxing, can cause considerable damage to the structures and sub-system in spite of a very small mass. However, it is not easy to detect the damage in composite plates using a single sensor or any conventional methods. In this paper, the PVDF sensors and AE sensors were used for monitoring high-velocity impact damage initiation and propagation in composite laminates. The WT(wavelet transform) is used to decompose the sensor signals. In the PVDF sensor and AE sensor signal analysis, amounts of high-frequency signals are increased when the impact energy is increased. PVDF sensor and AE sensor signal appeared similar results. This study shows how various sensing techniques can be used to characterize high-velocity impact damage of advanced composite laminates.

• Tunnel and Underground Space
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• v.27 no.5
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• pp.253-262
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• 2017

The purpose of this paper is to analyze the crack characteristics by performing the compression test of the rock and concrete specimens. The experiments are carried out by using strain sensors which can measure length change and the AE sensor which can detect the elastic wave from the crack. The crack volumetric strain calculated from measured strain is shown in different shape on the rock and the concrete specimens. This is because the specimens have a different degree of brittleness. However, the crack volumetric strain associated with the fracture and damage was similar to accumulated AE energy of the two specimens. This means that the AE sensor can assess damage in real time without damaging the structure.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.1
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• pp.1-7
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• 2007

As fiber reinforced composite materials are widely used in aircraft, space structures and robot arms, the study on non-destructive testing methods has become an important research area for improving their reliability and safety. AE (acoustic emission) can evaluate the defects by detecting the emitting strain energy when elastic waves are generated by the initiation and growth of crack, plastic deformation, fiber breakage, matrix cleavage, or delamination. In the paper, AE signals generated under uniaxial tension were measured and analyzed using the $8{\times}8$ matrix piezo electric sensor. The electronic circuit to control the transmitting distance of AE signals was designed and constructed. The optical data storage system was also designed to store the AE signal of 64channels using LED (light emitting diode) elements. From the tests, it was shown that the source location and propagation path of AE signals in composite materials could be detected effectively by the $8{\times}8$ matrix piezo electric sensor.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.41-46
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• 2003

This paper deals with the possibility of tap breakage detection by AE sensor. AE signals in the tapping were not seldom generated in low speed but reflected the tapping process exactly in high speed. Using AE raw signals sampled in 500kHz, AE RMS and AE count rate was computed in software. When the converting time of AE RMS is less than 10ms, we could distinguish between normal cutting and tap breakage. And AE count rate was more exact when the converting time is greater than 1ms. When two methods were compared to each other, AE count rate was more accurate.

• Journal of the KSME
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• v.30 no.5
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• pp.450-453
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• 1990

회전축(로터 안 구멍)과 정지부(베어링, 케이싱 등)에 AE 센서를 붙여 이들의 검출신호를 목적 으로 처리하는 것에 의해 회전체 주위의 이상진단을 수행하는 AE 시스템에 대해서 소개하였다. 회전측의 신호검출에는 무선식 전송방식을 이용하는 것이 유효하다고 생각된다. 또한 베어링에 설치한 AE 센서로부터 베어링의 손상진단이 가능하다는 것과 함께 래빙 발생위치도 알아낼 수 있다고 생각된다. 이 글에서는 회전기계의 이상진단에 관하여 극히 일부를 소개하였으나 AE 법을 이용한 각종 응용이 개발되리라고 기대된다.