• Title, Summary, Keyword: Acoustic Emission

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A Study on the Spectrum Analyzing of Internal Leak in Valve for Power Plant Using Acoustic Emission Method (음향방출법에 의한 발전용 밸브내부 누설의 스펙트럼분석 연구)

  • Lee, Sang-Guk;Lee, Sun-Ki;Lee, Jun-Shin;Sohn, Seok-Man
    • Proceedings of the KSME Conference
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    • pp.694-699
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    • 2004
  • The purpose of this study is to estimate the availability of acoustic emission method to the internal leak of the valves at nuclear power plants. The acoustic emission method was applied to the valves at the site, and the background noise was measured for the abnormal plant condition. From the comparison of the background noise data with the experimental results as to relation between leak flow and acoustic signal, the minimum leak flow rates that can be detected by acoustic signal was suggested. When the background levels are higher than the acoustic signal, the method described below was considered that the analysis the remainder among the background noise frequency spectrum and the acoustic signal spectrum become a very useful leak detection method. A few experimental examples of the spectrum analysis that varied the background noise characteristic were given.

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Analysis of acoustic emission parameters according to failure of rock specimens (암석시편 파괴에 따른 acoustic emission 특성인자 분석)

  • Lee, Jong-Won;Oh, Tae-Min;Kim, Hyunwoo;Kim, Min-Jun;Song, Ki-Il
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.21 no.5
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    • pp.657-673
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    • 2019
  • A monitoring method based on acoustic emission (AE) sensor has been widely used to evaluate the damage of structures in underground rock. The acoustic emission signal generated from cracking in material is analyzed as various acoustic emission parameters in time and frequency domain. To investigate from initial crack generation to final failure of rock material, it is important to understand the characteristics of acoustic emission parameters according to the stress ratio and rock strength. In this study, uniaxial compression tests were performed using very strong and weak rock specimen in order to investigate the acoustic emission parameters when the failure of specimen occurred. In the results of experimental tests, the event, root-mean-square (RMS) voltage, amplitude, and absolute energy of very strong rock specimen were larger than those of the weak rock specimen with an increase of stress ratio. In addition, the acoustic emission parameters related in frequency were more affected by specification (e.g., operation and resonant frequency) of sensors than the stress ratio or rock strength. It is expected that this study may be meaningful for evaluating the damage of underground rock when the health monitoring based on the acoustic emission technique will be performed.

A Study on the Measurement of Acoustic Emission and Deformation Behaviors of Rock and Concrete under Compression (암석 및 콘크리트의 압축변형거동과 미소파괴음 측정에 관한 연구)

  • 심현진;이정인
    • Tunnel and Underground Space
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    • v.10 no.1
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    • pp.59-69
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    • 2000
  • Acoustic emission is n burst of microseismic waves generated by microscopic failure due to deformation in materials. The study on the detection of initiation and propagation of microcracks from acoustic emission measurement is very important for the evaluation of the stability of underground rock structures by the nondestructive letting method. In this study, acoustic emission was measured under uniaxial stiffness loading test used to obtain the complete stress-strain curves of marble and concrete used as reinforced materials of rock structures. The analysis of acoustic emission parameters and source location were performed to discuss the characteristics of the deformation and failure behavior of rock and concrete. And acoustic emission was measured under cyclic loading test to verify the Kaiser effect associated with the damage of materials, in situ stress of rock, and stress history of concrete structure.

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Pre-service Acoustic Emission Testing for Metal Pressure Vessel (금속압력용기의 사용 전 음향방출시험)

  • Lee, Jong-O;Yoon, Woon-Ha;Lee, Tae-Hee;Lee, Jong-Kyu
    • Journal of the Korean Society for Nondestructive Testing
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    • v.23 no.3
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    • pp.280-284
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    • 2003
  • The field application of acoustic emission(AE) testing for brand-new metal pressure vessel were performed. We will introduce the test procedure for acoustic emission test such as instrument check distance between sensors, sensor location, whole system calibration, pressurization sequence, noise reduction and evaluation. The data of acoustic emission test contain many noise signal, these noise can be reduced by time filtering which based on the description of observation during AE test.

와이어 인발가공에 있어서 AE법의 적용에 관한 연구

  • 박준서;최만용;한응교;삼경언
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.95-100
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    • 1991
  • From a manufacturing standpoint it would be desirable to monitor the degradation of drawing die, that is essential for the maintenance of quality, the evaluation of product integrity and the reducing scrap. Acoustic emission is powerful method in monitoring fine wire drawing process, especially in detecting the die fracture at early stage. Experiments at so suggested that acoustic emission signals contained valuable information regarding the stage of a drawing process such as the surface appearance of products and the condition of lubrication. Using these informations makes AE monitoring techniques a possible tool in monitoring the drawing process operation. In order to approach this, this paper discusses the nature of acoustic emission signals produced in drawing process under various conditions. Experimental results are presented which illustrate the effects of wire and die material, lubricants, and drawing speed on the generation and the mean voltage level of acoustic emission signals. The results from these tests give controlling factors of acoustic emission generation.

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Development of a Diagnostic Algorithm with Acoustic Emission Sensors and Neural networks for Check Valves

  • Seong, Seung-Hwan;Kim, Jung-Soo;Hur, Seop;Kim, Jung-Tak;Park, Won-Man
    • Nuclear Engineering and Technology
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    • v.36 no.6
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    • pp.540-548
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    • 2004
  • Check valve failure is one of the worst problems in nuclear power plants. Recently, many researches have been based on new technology using accelerometers and ultrasonic and magnetic flux detection have been carried out. Here, we have suggested a method that uses acoustic emission sensors for detecting the failures of check valves through measuring and analyzing backward leakage flow, a system that works without disassembling the check valve. For validating the suggested acoustic emission sensor methodology, we designed a hydraulic test loop with a check valve. We have assumed in this study that check valve failure is caused by disk wear or by the insertion of a foreign object. In addition, we have developed diagnostic algorithms by using a neural network model to identify the type and size of the failure in the check valve. Our results show that the proposed diagnostic algorithm with acoustic emission sensors is a good solution for identifying check valve failure without necessitating any disassembly work.

A review of the application of acoustic emission technique in engineering

  • Gholizadeh, S.;Leman, Z.;Baharudin, B.T.H.T.
    • Structural Engineering and Mechanics
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    • v.54 no.6
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    • pp.1075-1095
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    • 2015
  • The use of acoustic emission (AE) technique for detecting and monitoring damages and the progress on damages in different structures is widely used and has earned a reputation as one of the most reliable and well-established technique in non-destructive testing (NDT). Acoustic Emission is a very efficient and effective technology used for fracture behavior and fatigue detection in metals, fiberglass, wood, composites, ceramics, concrete and plastics. It can also be used for detecting faults and pressure leaks in vessels, tanks, pipes, as well as for monitoring the progression of corrosion in welding. This paper reviews major research developments over the past few years in application of acoustic emission in numerous engineering fields, including manufacturing, civil, aerospace and material engineering.

A Study on Degradation Characteristic of High Strength Fire Resistance Steel for Frame Structure by Acoustic Emission (음향방출법에 의한 고강도 구조요 내화강의 열화특성에 관한 연구)

  • 김현수;남기우;강창룡
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.51-56
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    • 2000
  • Demand for new nondestructive evaluations is growing to detect tensile crack growth behavior to predict long term performance of materials and structure in aggressive environments, especially when they are in non-visible area. Acoustic emission technique is well suited to these problems and has drawn a keen interests because of its dynamic detection ability, extreme sensitivity and location of growing defects. In this study, we analysed acoustic emission signals obtained in tensile test of high strength fire resistance steel for frame structure with time frequency analysis methods. The results obtained are summaries as follows ; In the T and TN specimen consisting of ferrite and pearlite grains, most of acoustic emission events were produced near yield point, mainly due to the dislocation activities during the deformation. However, B specimen under $600^{\circ}C$ - 10min had a two peak which was attribute to the presence of martensite phase. The first peak is before yield point the second is after yield point. The sources of second acoustic emission peak were the debonding of martensite-martensite interface and the micro-cracking of brittle martensite phase. In $600^{\circ}C$-30min to $700^{\circ}C$-60min specimens, many signals were observed from area before yield point and counts were decreased after yield point.

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A Study on the Wavelet Transform of Acoustic Emission Signals Generated from Fusion-Welded Butt Joints in Steel during Tensile Test and its Applications (맞대기 용접 이음재 인장시험에서 발생한 음향방출 신호의 웨이블릿 변환과 응용)

  • Rhee, Zhang-Kyu
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.16 no.1
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    • pp.26-32
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    • 2007
  • This study was carried out fusion-welded butt joints in SWS 490A high strength steel subjected to tensile test that load-deflection curve. The windowed or short-time Fourier transform(WFT or STFT) makes possible for the analysis of non-stationary or transient signals into a joint time-frequency domain and the wavelet transform(WT) is used to decompose the acoustic emission(AE) signal into various discrete series of sequences over different frequency bands. In this paper, for acoustic emission signal analysis to use a continuous wavelet transform, in which the Gabor wavelet base on a Gaussian window function is applied to the time-frequency domain. A wavelet transform is demonstrated and the plots are very powerful in the recognition of the acoustic emission features. As a result, the technique of acoustic emission is ideally suited to study variables which control time and stress dependent fracture or damage process in metallic materials.

Tree-dimensional FE Analysis of Acoustic Emission of Fiber Breakage using Explicit Time Integration Method (외연적 시간적분법을 이용한 복합재료 섬유 파단 시 음향방출의 3차원 유한요소 해석)

  • Paik, Seung-Hoon;Park, Si-Hyong;Kim, Seung-Jo
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.172-175
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    • 2005
  • The numerical simulation is performed for the acoustic emission and the wave propagation due to fiber breakage in single fiber composite plates by the finite element transient analysis. The acoustic emission and the following wave motions from a fiber breakage under a static loading is simulated to investigate the applicability of the explicit finite element method and the equivalent volume force model as a simulation tool of wave propagation and a modeling technique of an acoustic emission. For such a simple case of the damage event under static loading, various parameters affecting the wave motion are investigated for reliable simulations of the impact damage event. The high velocity and the small wave length of the acoustic emission require a refined analysis with dense distribution of the finite element and a small time step. In order to fulfill the requirement for capturing the exact wave propagation and to cover the 3-D simulation, we utilize the parallel FE transient analysis code and the parallel computing technology.

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