• Title, Summary, Keyword: Acoustic Emission

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The Relation between Treeing Breakdown Prediction and Acoustic Emission in Low Density Polyethylene (저밀도 폴리에틸렌의 트리 파괴 예지와 음향방출과의 관계)

  • 백관현;심종탁;김재환
    • The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.8 no.2
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    • pp.77-84
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    • 1994
  • This paper is measured partial discharge of low density polyethylene by using acoustic emission measuring method when the electrical tree grow its length in LDPE. Acoustic emission's pulses and its amplitudes of partial discharge are measured by acoustic emission measuring devices. Theorem of skewness are used for breakdown prediction of LDPE. So, it is found that the breakdown of LDPE could be predicted by its skewness's value. There are two kind of specimen of no void and specimen of artificial void, this one's electrical tree grows very faster than that one's.

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Experimental observation and realistic modeling of initiation and propagation of the rock fracture by acoustic emission

  • Wang, Shu-Hong;Lee, Chung-In;Jeon, Seok-Won;Lee, Hee-Kwang;Tang, Chun-An
    • Proceedings of the Korean Society for Rock Mechanics Conference
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    • pp.79-93
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    • 2006
  • It is well known that acoustic emission (AE) is indicator of rock fracturing or damage as rock is brought to failure under the uniaxial compressive loads. In this paper, an experimental study on the source location of acoustic emission on the cylindrical specimens of granite under uniaxial compression test was made. The AE source location was made by measuring the six channel AE data. Comparing to this experiment, the numerical method is applied to model the initiation and propagation of fracture by AE using a numerical code, RFPA (Realistic Failure Process Analysis). This code incorporates the mesoscopic heterogeneity in Young's modulus and rock strength characteristic of rock masses. In the numerical models, values of Young's modulus and rock strength are realized according to a Weibull distribution in which the distribution parameters represent the level of heterogeneity of the medium. The results of the simulations show that RFPA can be used not only to produce acoustic emission similar to those measurements in our experiments, but also to predict fracturing patterns under uniaxial loading condition.

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Location of Acoustic Emission Sources in a PSC Beam using Least Squares (최소제곱법에 의한 PSC보의 음향방출파원 위치결정)

  • Lee Chang-No
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.24 no.3
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    • pp.271-279
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    • 2006
  • Acoustic Emission (AE) technology is an effective nondestructive testing for continuous monitoring of defect formation and failures in structural materials. This paper presents a source location model using Acoustic Emission (AE) sensors in a Pre-Stressed Concrete (PSC) beam and the evaluation of the model was performed through lab experiments. 54 AE events were made on the surface of the 5m-PSC beam using a Schmidt Hammer and arrival times were measured with 7AE sensors. The source location f3r each event was estimated using least squares. The results were compared with actual positions and the RMSE (Root Mean Square Errors) was about 2cm.

A Study on the characteristics of the Signals of AE according to Fracture mode of CFRP (Carbon Fiber Reinforced Plastic(CFRP)복합재의 파괴 거동에 따른 Acoustic Emission(AE)신호 특성에 관한 연구)

  • Lee, Kyung-Won;Kim, Jong-Hyun;Kim, Jae-Seong;Lee, Bo-Young
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.17 no.4
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    • pp.42-47
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    • 2009
  • Recently, the wide range of the composite materials is used for the making airplanes, trains and automobiles body for the lightweight. Despite having complex structures, composite materials usually have well defined mechanical characteristics. However, composite materials are difficult to understand the fracture mechanism clearly by simple mechanical test. Nondestructive evaluation (NDE) combined with mechanical testing can play a more important role and especially Acoustic Emission Testing (AET) would become known to be a useful tool to assess damage and fracture behavior of composites. In this study The experiment was performed to acquire the acoustic emission signal during tensile test using unidirectional CFRP specimen and the data was analyzed the acoustic emission parameters with the waveform.

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Acoustic Emission Characteristics of Notched Aluminum Plate Repaired with a Composite Patch (복합재 패치로 보수된 노치형 알루미늄 합금 평판의 음향방출 특성)

  • Yoon, Hyun-Sung;Choi, Nak-Sam
    • Journal of the Korean Society for Nondestructive Testing
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    • v.31 no.1
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    • pp.53-61
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    • 2011
  • Edge notched A16061-T6 aluminum was repaired with a GFRP composite patch as a function of the number of stacking, Damage progress of specimen for tension load has been monitored by acoustic emission(AE), AE energy rate, hit rate, amplitude, waveform and 1st peak frequency distribution were analyzed. Fracture processes were classified into Al cracking, Fiber breakage, Resin cracking and Delamination. Displacement of a specimen can be divided into Region I, II and ill according to acoustic emission characteristics. Region II where the patch itself was actually fractured was focused on to clarify the AE characteristics difference for the number of stacking.

Identification of Damage Characteristics Due to Cracking of Concrete Structures Using Acoustic Emission (음향방출 특성을 이용한 콘크리트 부재종류 및 하중상태에 따른 균열손상 연구)

  • 오병환;김응재;김광수;유성원
    • Journal of the Korea Concrete Institute
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    • v.11 no.4
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    • pp.107-116
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    • 1999
  • The damage in concrete structures generally starts with microcracking and thus it is important to find and explore these microcracks in concrete in order to ensure appropriate safety and serviceability. The purpose of the present study is to identify the damage characteristics of concrete structures due to cracking by employing the acoustic emission techniques. A comprehensive experimental study has been done. The cracking damage under tensile and flexural loadings have been identified and the bond damage between steel and concrete have been also characterized. It is seen that the amplitudes and energy level of Acoustic Emission(AE) events are found to be relatively small for bond cracking damages and large for tensile cracking damages. The characteristic equations of the AE events for various cracking damages have been proposed based on the present test data. The internal microcracks are progressively developed ahead of a visible actual crack and the present study clearly exhibits these damage mechanism for various types of cracking in concrete. The present study provides useful data which can be used to identify the various types of cracking damages in concrete structures. This will allow efficient maintenance of concrete structures through monitoring of internal cracking based on acoustic emission.

Nondestructive Testing and Applications for Integrity Assessment of Power Plant Facilities by Acoustic Emission Technology - Part 1 : The Theory of Acoustic Emission Technology(I) - (발전설비 건전성평가를 위한 음향방출 비파괴검사 적용기술 - 제1편 : 음향방출 비파괴검사기술 이론(I) -)

  • Lee, S.G.
    • Journal of Power System Engineering
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    • v.9 no.1
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    • pp.5-13
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    • 2005
  • Acoustic emission(AE) is defined as the transient elastic waves thar are generated by the rapid release of energy. The advantage of AE is that very early crack growth can be detected well before a highly stressed component may fail. At present, an exact diagnosis is the most reliable means for determining the soundness of structures during power plant operations. AE monitoring has been applied successfully in power plants to determine mechanical problems, pressure vessel integrity and external valves leaks, vacuum leaks, the onset of cavitation in pumps and valves, the presence of flow(or no flow) in piping and heat exchange equipment, etc. Acoustic emission(AE) technology has recently strengthened its application base, and practitioners' understanding of the technique's fundamentals. This paper introduces the methods of a survey and assessment on AE monitoring applications in nuclear, fossil and hydraulic power plant. The main objective of this paper was to obtain information on various applications of AE technology in power plant.

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Surface Crack Detection in Compression of Pre Heat-Treated Steel (ESW90) Using an Acoustic Emission Sensor (음향방출센서를 이용한 선조질강(ESW90)의 압축실험에서의 표면 균열 발생 검출)

  • Lee, J.E.;Lee, J.M.;Joo, H.S.;Seo, Y.H.;Kim, J.H.;Kim, S.W.
    • Transactions of Materials Processing
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    • v.29 no.1
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    • pp.20-26
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    • 2020
  • In the design of the metal forming processes, various types of ductile fracture criteria are used to predict crack initiation and to fabricate metallic products without any defects. However, the quantitative measurement method for determination of crack initiation is insufficient. It is very difficult to detect crack initiation in ductile metals with excellent deformability because no significant load drop is observed due to crack generation. In this study, the applicability of acoustic emission sensors, which are commonly used in facility diagnostics, to measure crack initiation during the metal forming process was analyzed. Cylindrical notch specimens were designed using the finite element method to induce a premature crack on the surface of pre heat-treated steel (ESW90) material. In addition, specimens with various notch angles and heights were prepared and compression tests were carried out. During the compression tests, acoustic emission signal on the dies and images of the surface of the notch specimen were recorded using an optical camera in real time. The experimental results revealed that the acoustic emission sensor can be used to detect crack initiation in ductile metals due to severe plastic deformation.

Thermo-Acoustic Emission Behavior of Composites (복합재료의 열-음향방출거동)

  • 김영복;우성충;최낙삼
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.111-115
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    • 2001
  • Thermo-acoustic emission (AE) from composite laminates under the repetitive thermal cyclic loads have been quantitatively analyzed in consideration of AE source mechanisms. The repetitive thermal load brought about a large reduction, i.e. an exponential decrease in AE total ringdown counts and AE amplitudes. It was thought that generation of thermo-AE during the first thermal cycle was not caused by crack propagation but by secondary microfracturing due to abrasive contact between crack surfaces.

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Prediction of Chip Formation Mechanism Using Acoustic Emission (음향방출을 이용한 칩 발생 기구의 예측)

  • 맹민재
    • Journal of the Korean Society of Safety
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    • v.16 no.2
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    • pp.22-26
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    • 2001
  • The machining process on be considered as a planned interaction of the workpiece, the tool and the machine tool. In an unmanned situation, the results of this interaction are to be continuously monitored so that any changes in the machining environment on be sensed to corrective actions. In order to design the process monitoring system for unmanned manufacturing, the identification of chip formation is proposed. The system proposes the method of using acoustic emission(AE) signal analysis to identify the chip formation during cutting.

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