• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.39-40
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• 2006

AE sensor using lead-free ceramics should be developed for prohibiting environment protection. In this study, Langevin type AE sensor was manufactured as air backing structure. Here, the piezoelectic element was used as PZT(EC-65) and NKN, respectively. The resonant frequency of AE sensor using PZT was 143 kHz and the resonant frequency of AE sensor using NKN was 178 kHz. The waveform of AE sensor using NKN was responded more sensitively than that of AE sensor using PZT.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.6
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• pp.502-508
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• 2000

In order to detect the partial discharge with the metallic particle in GIS the AE(Acoustic Emission) sensor was designed and simulated by ANSYS 5.5 and manufactured as the coupled vibration mode. The measured resonant frequency and the maximum sensitivity frequency of three coupled AE sensors were as follows ; 147.88 kHz in 8.1mm $\Phi$$\times$8.1mm 128.82 kHz and 58.8 kHz in 9.5 mm$\Phi$$\times$9.5mm, 85.22 kHz and 32.6 kHz in 14.3 mm$\Phi$$\times$14.3 mm, resonant frequency of the AE sensor. The AE sensor of 9.5 mm$\Phi$$\times$9.5mm responded higher than the other coupled vibration mode AE sensor at the partial discharge detection in GIS.

• Proceedings of the KIEE Conference
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• 2000.07e
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• pp.52-55
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• 2000

In this paper, the coupled and the non-coupled vibration mode AE sensor for GIS were simulated by finite element analysis and manufactured, and characterized. The maximum sensitivity was 64.3 dB when the resonant frequency of the coupled vibration mode AE sensor was 166 kHz and the maximum sensitivity was 58.9 dB when the resonant frequency of the non-coupled mode AE sensor was 265 kHz. The coupled vibration mode AE sensor responded higher than the non-coupled vibration mode AE sensor at the partial discharge detection in GIS.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.286-289
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• 1999

In order to detect the partial discharge with the metallic particle in GIS, AE sensor was designed and simulated by ANSYS, and manufactured as the coupled vibration mode. The resonant frequency of three Coupled AE sensors were as follows ; 147.88 kHz in 8.1 mm$\Phi$ $\times$ 8.1mm, 128.82 kHz in 9.5 mm$\Phi$ $\times$ 9.5mm, 85.22 kHz in 14.3mm$\Phi$ $\times$14.3mm. That frequency is λ/2 resonant frequency. AE sensor of 9.5mm$\Phi$ $\times$9.5mm responded higher than the other coupled vibration mode AE sensor at the partial discharge detection in GIS.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.315-318
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• 1997

In terms of productivity, the speed of machining process has been increasing in most of engineering part. But the tapping process does not reach at enough level compared with other machining processes because of its complicate cutting mechanism. In the high speed tapping process, the one of important elements is tool monitoring system to prevent tool breakage. This paper describes tool monitoring system by acoustic emission(AE) in the tapping process. We used 2 types of AE sensors in this test. The one is commercial sensor which is used in other machining monitoring system like polishing and the other is a self-fabricated sensor for this test. In this test we purpose to find out the frequency of AE signal in tapping process and verify the possibility of applying AE sensor in in-process tapping monitoring system. Also grasp of characteristic of tapping process by AE signal is handled.

• 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 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.560-565
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• 2001

Recently, machining process monitoring technique based on AE(acoustic emission) signal is used widely and becomes very important technique in machining process for improving the efficiency and the confidence of the systems. In this study, we fabricated a cheap acoustic emission sensor and monitoring system and estimated the properties of them through comparing with commercial AE sensor systems. In addition, we evaluated the performance of the fabricated sensor in polishing process. Futhermore, we are scheduled to develop the multi-point polishing process monitoring system through fabrication of the more AE sensors and complement of the monitoring system.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3383-3388
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• 2007

To compare the sensor performance of AE leak diagnosis system which can measure valve leak conditions, AE activities such as RMS voltage level, AE signal trend, leak rate degree according to AE database, FFT spectrum were measured on valve of the simulated test system for power plant. AE activities were recorded and analyzed from various operating conditions including different temperature, pressure difference, valve size and fluid using both piezoelectric acoustic emission sensor and Pb-Free acoustic emission sensor. The results of this study are utilized to select the type of sensors, the frequency band for filtering and thereby to improve the signal-to-noise ratio for diagnosis or monitoring of valves in operation. As the final result of application study above, portable type leak diagnosis system by AE was developed. The outcome of the study can be definitely applied as a means of the diagnosis or monitoring system for energy saving and prevention of accident for power plant valve.

• Composites Research
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• v.27 no.4
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• pp.152-157
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• 2014

Non-destructive testing methods of composite materials are very important for improving material reliability and safety. AE measurement is based on the detection of microscopic surface movements from stress waves in a material during the fracture process. The examination of AE is a useful tool for the sensitive detection and location of active damage in polymer and composite materials. FBG (Fiber Bragg Grating) sensors have attracted much interest owing to the important advantages of optical fiber sensing. Compared to conventional electronic sensors, fiber-optical sensors are known for their high resolution and high accuracy. Furthermore, they offer important advantages such as immunity to electromagnetic interference, and electrically passive operation. In this paper, the crack detection capability of AE (Acoustic Emission) measurement was compared with that of an FBG sensor under tensile testing and buckling test of composite materials. The AE signals of the PVDF sensor were measured and an AE signal analyzer, which had a low pass filter and a resonance filter, was designed and fabricated. Also, the wavelength variation of the FBG sensor was measured and its strain was calculated. Calculated strains were compared with those determined by finite element analysis.