• 대한기계학회논문집
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• 제13권1호
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• pp.96-104
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• 1989

본 연구에서는 AE법에 의해 J$_{IC}$를 결정하는 것은 Takahashi등의 방법을 따르되 AE 실험결과를 토대로 이론을 전개하여 재료의 물성 곡선인 J-R곡선의 실험식과 재료 찢어짐 계수를 계산할 수 있는 실험식을 유도하며, 이렇게 구한 실험식을 불안정 파괴 조건에 적용하여 그 타당성을 검토한다.다.

• 한국생산제조학회지
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• 제19권1호
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• pp.7-14
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• 2010

AE(acoustic emission) sensor has been used for a state monitoring and observation during a ultra-precision machining because AE signal, which has high frequency range, is sensitive enough. In case of ceramic fabrication, a monitoring of machining state is important because of its hard and brittle nature. A machining characteristic of ceramic is susceptibly different in accordance with variable machining conditions. In this study, Yttria($Y_2O_3$) ceramic was fabricated using the ultra-precision lapping process with in-process electrolytic dressing(IED) method. And the surface machining characteristic and AE sensor signal were compared and analyzed.

• 한국안전학회지
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• 제20권1호
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• pp.49-54
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• 2005

Recently, many kinds of advanced composite materials have been used in various industry fields. Among them, fabric CFRP composites are being used as primary structural components in many applications because of their superior properties. However, the complexity of the fabric structure makes understanding of their failure behavior very difficult. The mechanical strength and crack propagation of plain woven carbon fiber fabric laminate composites are examined by acoustic emission(AE) method. AE signals are acquired during the tensile test and fracture tests. Thus, the relationship between AE signal and mechanical behavior curves and crack extension length are shown. Also the interlaminar fracture toughness in terms of AE characteristics are discussed in viewpoint of crack propagation behavior.

• 지질공학
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• 제25권4호
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• pp.587-598
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• 2015

이 연구에서는 기존의 다양한 미소파괴음(AE)의 신호 도달시간 결정방법을 검토한 후, 전산처리 프로그래밍이 용이하고 자료처리 속도가 빠른 가변 검출한계법을 개발하였다. 가변 검출한계법은 기존의 검출한계법을 수정한 것으로서, 검출한계 값을 하나로 고정하지 않고 측정된 모든 AE 신호마다 배경잡음 분석을 실시하여 각 신호에 맞는 검출한계 값을 결정하는 방법이다. 가변 검출한계법의 효과를 검토하기 위해 2차원과 3차원 음원추적 모델을 구성하고 실험적 방법으로 검증을 실시하였다. 2차원 모델에 대한 검증에서 가변 검출한계법을 적용할 경우 기존의 고정된 검출한계 값을 사용하는 방법에 비해 정확도가 평균 약 38.3% 정도 향상되는 것을 확인하였다. 3차원 모델에 대한 검증에서는 2차원 모델에 비해 다소 적으나 가변 검출한계법을 적용할 경우 평균 약 15.2% 정도의 정확도가 향상되는 것으로 분석되었으며, 3점 휨 시험에서도 가변 검출한계법이 적용된 분석 결과가 실제 파괴면과 더 높은 연관성을 보였다. 따라서 가변 검출한 계법이 AE 음원의 위치를 정확히 분석하는데 유용한 알고리즘이라는 것을 검증시험으로부터 확인할 수 있었다.

• Journal of Welding and Joining
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• 제15권2호
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• pp.43-53
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• 1997

The complete joining method for dissimilar press punch materials and its real-time evaluation method is not available at present. Brazing method has been used for joining them, but it is known that the welded joint by the brazing has the lower bonding efficiency and reliability than the diffusion welding. The friction welding with a diffusion mechanism in bonding was applied in this study. This work was carried out to determine the proper friction welding conditions and to analyze mechanical properties of friction welded joints of sintered carbide tool materials (SKNM50 for the blade part of press punch) to alloy steel (SCM440 for the shank part of press punch) using aluminum (A6061 for the interlayer material) as an insert material between the sintered carbide tool materials and the alloy steel. In addition, acoustic emission test was carried out during friction welding to evaluate the weld quality.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.198-205
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• 2003

We considered the variation of elastic wave velocity due to the anisotropy of rock materials and stress level for acoustic emission (AE) source location in cylindrical rock specimens. Elastic wave velocity and AE were measured for Keochang granite and Yeosan marble under various axial stresses and confining pressures. Partition approximation method was suggested and it was compared with the difference approximation method and the least square method.

• 한국해양공학회지
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• 제15권4호
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• pp.60-65
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• 2001

Thermal spray coating is formed by a process in which melted particles flying with high speed towards substrate, then crash and spread on the substrate surface cooled and solidified in a very short time, Stacking of the particles makes coating. In this study, the exfoliation of $Al_2$O$_3$ and Ni-4.5wt.%Al thermally sprayed coating which were deposited by an atmospheric plasma spray apparatus are investigated using an AE method. A tensile test is conducted on notch specimens in a stress range below the elastic limit of substrate. The wave forms of AE generated from the three coating specimens can be classified by FFT analysis into two types which low frequency(type I waveform is considered to corresponds exfoliation of coating layers and type II waveform corresponds the plastic deformation of notch tip or the resultant fracture of coating. The fracture of the coating layers can estimate by AE event and amplitude, because AE features increase when the deformation generates.

• KSTLE International Journal
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• 제1권1호
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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.

• 한국해양공학회지
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• 제16권2호
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• pp.67-71
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• 2002

Damage process of CFRP laminates was characterized by Acoustic Emission (AE). The main objective of this study is to determine if the sources of AE in CERP laminates could be identified from the characteristics of the waveform signals recorded during monotonic tensile test. The time history and power spectrum of each individual wave signal recorded during test were examined and classified according to their special characteristics. The wave from and frequency of AE signal from a specimens is an aid to the determination of the extent of the different fracture mechanism such as matrix crack, debonding, fiber pull-out and fiber fracture as load is increased. Four distinct types of signals were observed regardless of specimen condition. The result showed that the AE method could be effectively used for analysis of fracture mechanism in CFRP laminates.

• 한국산업융합학회 논문집
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• 제2권2호
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• pp.147-153
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• 1999

An in-process extraction method of the ground surface roughness is a bottle-neck and essential field in conventional machining process. We define the D.A.R.F(Dimensionless Average Roughness Factor) that has a roughness characteristic of ground surface. D.A.R.F include the absolute average and the standard deviation values which are the analytic parameters of the AE(Acoustic Emission) signal generated during the grinding operation. The theoretical equation between the surface roughness and the D.A.R.F has been derived from the linear regressive analysis and verified its availability through the experimentation on the surface grinding machine.