• Title, Summary, Keyword: Acoustic Emission

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Effects of Acoustic Excitation on NOx Emission in Partially Premixed LPG/Air Flames (부분적 예혼합 LPG/공기 화염에서 음향자진이 NOx 배출에 미치는 영향)

  • 장준영;박성호;김태권
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.3
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    • pp.77-84
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    • 2002
  • Measurements of NO and NOx emission of laminar partially premixed LPG/air flames with and without acoustic excitation are reported. The NOx emission at the tailpipe of a combustion chamber is determined by chemiluminescent analyser. The NOx measurements are taken in flames with several different center tube equivalance ratio( ø$\sub$o/), and overall equivalace ratio(ø$\sub$o/) for a fixed fuel flowrate. The NOx emission decrease to reach a minimum value at an optimum ø$\sub$c/ 2. Theø$\sub$c/ 2 flame gives a compromise of thermal NO and prompt NO mechanism. In the case of excitation. the visual shape of the flame is changed from laminar flame to turbulent-like flame. With increasing levels of excitation amplitude, an optimum value of the NO and NOx emission exists. A shorter flame caused by the enhanced upstream mixing due to acoustic excitation results in the reduction of NO and NOx emission in the present flames. The reduction of flame length affects the shorter residence time of center tube mixture, and significantly influences the NOx reduction.

Interpretation of AE Signals from Rocket Motor Case Assembly (로켓 연소관 조립체의 음향방출 신호해석)

  • Rhee, Sang-Ho;Hwang, Tae-Kyong;Mun, Sun-Il
    • Journal of the Korean Society for Nondestructive Testing
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    • v.23 no.5
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    • pp.488-496
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    • 2003
  • To establish nondestructive test method for rocket motor assembly with rubber and aerospace composite materials, practicable quality control acoustic emission test method is presented. Structural analysis for motor assembly is performed by ABAQUS code and analysis output result is confirmed by strain gage and AE data. Various specimens were tested and analyzed using strain gage and acoustic emission data. The hit rate of acoustic emission was closely related with case/rubber debonding. This report also describes practicable acoustic emission nondestructive method for evaluating motor case assembly quality assurance in the industrial field.

Acoustic emission behavior during fatigue crack propagation in 304 Stainless steel (피로균열진전에 따른 304 강의 음향방출 거동)

  • Oh, Kwang-Hwan;Jung, Chang-Kyu;Yang, Yoo-Chang;Han, Kyung-Seop
    • Proceedings of the KSME Conference
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    • pp.213-219
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    • 2003
  • Acoustic emission behavior during fatigue crack growth test was investigated under various loading condition. To describe the acoustic emission activity, counts rate (d/dn) was related with SIFR (stress intensity factor range, K). Results indicated that SIFR could be divided into two parts according to its relationship with counts rate. For $K<25_{MPa\sqrt{m}}$, counts rate was increased as the SIFR increased. However, for values greater than $25_{MPa\sqrt{m}}$ , decreasing behavior was shown. This behavior of counts rate corresponding SIFR was keeping the same trend regardless of load range or crack length. Acoustic emission response to the single overload was sudden drop and slow recovery in counts rate like crack growth retardation. Under variable loading condition, counts rate of each loading block was same as that of constant amplitude loading. Overall experimental data was somewhat scattered since sensitive characteristics of acoustic emission method. However, these empirical relations indicated that counts rate was uniquely correlate with single parameter, SIFR.

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A Study On the Diagnosis Breakdown Using Fractal Characteristics and the Method of Acoustic Emission in Low Density Polyethylene (프랙탈 특성과 음향방출 계측법을 이용한 LDPE 시료에서의 트리잉 파괴진단에 관한 연구)

  • Yoon, H.J.;Park, J.J.;Shin, S.J.;Choi, J.K.;Kim, S.H.;Kim, J.H.
    • Proceedings of the KIEE Conference
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    • pp.1758-1760
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    • 1997
  • Automatic detection system to detect acoustic emission pulse and fractal dimension were developed, to observe tree deterioration phenomena in LDPE. The purpose of our work are to use acoustic emission system and fractal dimension and to investigate the treeing phenomena in polymeric insulation under applied AC voltage 11[kV] with an artificial needle-shaped void(1.5[mm]) using the above system. We analyzed and phase angle-acoustic emission pulse amplitude-deterioration time ($\Phi$-AEA-t) pattern and phase angle-acoustic emission pulse number-deterioration time($\Phi$-AEN-t) pattern using statistical operators such as skewness, fractal dimension. In this paper show that the correlation of $\Phi$-AEA-t, $\Phi$-AEN-t, fractal dimension using regression analysis by the method of least squares can be used to predict the breakdown just before the breakdown occurs.

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ACOUSTIC EMISSION CHARACTERISTIC OF THE RAT FEMUR AFTER ADMINISTRATION OF SODIUM FLUORIDE (불소섭취에 따른 백서 대퇴골의 파절특성에 관한 Acoustic Emission 연구)

  • Song, Keun-Bae;Lee, Young-Eun;Kim, Hye-Young;Lee, Sang-Han
    • Journal of the Korean Association of Oral and Maxillofacial Surgeons
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    • v.28 no.1
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    • pp.16-23
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    • 2002
  • To understand the micro-mechanical changes and the effects of the fluoride on rat's femur after administration of sodium fluoride, the three-point bending test, acoustic emission analysis during the three-point bending test and scanning electron microscopy were performed. The obtained results were as follows: 1. Bone strength increased in the rats given 1, 5, 10 and 20 ppm of fluoride but, there were no statistical significances (p>0.05). 2. With increasing the concentration of fluoride, most AE events released rapidly just before the maximum load and smaller events were recorded than the control group's. The average of cumulative AE event counts until maximum load of the femur in 20 ppm group were significantly small with respect to the control group's (p<0.05). 3. Fracture surfaces were well coincide with the results of acoustic emission behavior. Analyses of fracture surfaces indicated that, consistent with its the highest load, rat femur in 20 ppm fluoride group displays the roughest surface.

A study on the investigation of AE during orthogonal metal cutting (2次元 切削時 發생하는 AE에 관한 硏究)

  • Kang, Myung-Soon;Choi, Seong-Joo;Park, Hyun
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.10 no.6
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    • pp.906-915
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    • 1986
  • This study reviewed the theory of acoustic emission applying generation of acoustic emission in metal cutting and proposed a relationship between fundamental cutting parameters and the root mean square (RMS) voltage of the acoustic emission on the basis of the mechanics of the orthogonal cutting operation. Experimental results are presented for 6063-T5 Auminum and the validity of this relationship is evaluated by a series of tests varying cutting speed, feed rate and rake angle in orthogonal cutting. The original formula derived theoretically has been modified in order to utilize independent of fundamental cutting parameters. RMS voltage of acoustic emission depends on cutting speed and strain rate, but it is not much affected by feed rate. Applying lubricant, the drop of RMS level has been observed.

Application of Acoustic Emission Technique for On-Line Monitoring of Quench in Racetrack Superconducting Coil at Cryogenic Environment (음향방출기법을 이용한 극저온 환경하에서 초전도 계자코일의 퀀칭탐지 적용에 관한 연구)

  • Lee, Min-Rae;Gwon, Yeong-Gil;Lee, Jun-Hyeon;Son, Myeong-Hwan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.4
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    • pp.858-865
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    • 2000
  • It is well recently recognized that quench is one of the serious problems for the integrity of superconducting magnets, which is mainly attribute to the rapid temperature rising in the magnet due to some extrinsic factors such as conductor motion, crack initiation etc. In order to apply acoustic emission(AE)echnique effectively to monitor and diagnose superconducting magnets, it is essential to identify the sources of acoustic emission. In this paper, an acoustic emission technique has been used to monitor and diagnose quenching phenomenon in racetrack shaped superconducting magnets at cryogenic environment of 4.2K. For these purposes special attention was paid to detect AE signals associated with the quench of superconducting magnets. The characteristics of AE parameters have been analyzed by correlating with quench number, winding tension of superconducting coil and charge rate by transport current. In addition, the source location of quench in superconducting magnet was also discussed on the basis of correlation between magnet voltage and AE energy.

Application of Technique Discrete Wavelet Transform for Acoustic Emission Signals (음향방출신호에 대한 이산웨이블릿 변환기법의 적용)

  • 박재준;김면수;김민수;김진승;백관현;송영철;김성홍;권동진
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.585-591
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    • 2000
  • The wavelet transform is the most recent technique for processing signals with time-varying spectra. In this paper, the wavelet transform is utilized to improved the assessment and multi-resolution analysis of acoustic emission signals generating in partial discharge. This paper especially deals with the assessment of process statistical parameter using the features extracted from the wavelet coefficients of measured acoustic emission signals in case of applied voltage 20[kv]. Since the parameter assessment using all wavelet coefficients will often turn out leads to inefficient or inaccurate results, we selected that level-3 stage of multi decomposition in discrete wavelet transform. We applied FIR(Finite Impulse Response)digital filter algorithm in discrete to suppression for random noise. The white noise be included high frequency component denoised as decomposition of discrete wavelet transform level-3. We make use of the feature extraction parameter namely, maximum value of acoustic emission signal, average value, dispersion, skewness, kurtosis, etc. The effectiveness of this new method has been verified on ability a diagnosis transformer go through feature extraction in stage of acting(the early period, the last period) .

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Study of Fracture Toughness Measurement and Fracture Stability Evaluation by Acoustic Emission Method (음향 방출법에 의한 파괴 인성치 측정 및 파괴 안정성 평가를 위한 연구)

  • 이강용;백충헌
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.1
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    • pp.96-104
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    • 1989
  • The behaviors of acoustic emission emitted in the tests of the fracture toughness and fracture stability are observed by using the specimens of aluminum 2024-T351 and 7039-T6 alloys. The empirical eqution of J-R curve is derived. It is demonstrated from the comparison of the fracture toughness obtained from J-R curve with that from ASTM standard E813-81 that the latter is larger than the former. The discontinuous point in the log-log graph of J-integral vs. total acoustic emission count is observed in between the two offset lines referred from ASTM standard E813-81, but it's physical meaning is uncretain. An empirical material tearing modulus is derived in terms of the total acoustic emission count and proved to be valid in fracture instability test.

ACOUSTIC EMISSION ANALYSIS FOR FRACTURE CHARACTERISTICS OF DENTAL POSTERIOR COMPOSITES (구치부 수복용 복합레진의 파괴특성에 관한 Acoustic Emission 연구)

  • Park, Jin-Hoon;Kim, Kyo-Han
    • Restorative Dentistry and Endodontics
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    • v.17 no.1
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    • pp.153-165
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    • 1992
  • Dental composite resin is a kind of the particle - reinforced composite material, and is widely used in recent dental restoration of anterior and posterior tooth region. The purpose of this study was to investigate the fracture behaviour according to volume fractions and external findings of the filler particles for better interpretation of the fracture characteristics of posterior dental composite resins by analytic method of fracture mechanics. The plane strain fracture toughness($K_{IC}$) and Acoustic Emission were determined with three - point bending test using the single edge notch specimen according to the ASTM - E399, and its analyzed data was compared with filler volume fractions derived from the standard ashing test and scanning electron fractographs of each specimen including the unfilled experimental resin as a control. The results were that the value of fracture toughness of the composite resin material was in the range from 0.85 MPa$\sqrt{m}$ to 1.60 MPa$\sqrt{m}$ and was higher than the value of the unfilled experimental resin, and the fracture behaviours dervied from Acoustic Emission analysis show prominent differences according to the volume fraction and the size of filler particles used in each composite resin. The degree of resistance against crack propagation seems to be increase and the fractographs demonstrate the high degree of surface roughness and irregularity according with the increase of fracture toughness value.

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