• Title/Summary/Keyword: AE Counts

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Evaluation of Grade of WA-Vitrified and Resinoid Bond Grinding Wheels by Acoustic Emission (AE에 의한 WA계 비트리파이드 및 레지노이드 결합제 연삭숫돌의 결합도 평가)

  • Joung, In-Kuen;Lim, Young-Ho;Kwon, Dong-Ho
    • Journal of the Korean Society for Precision Engineering
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    • v.12 no.9
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    • pp.74-85
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    • 1995
  • The purpose of this paper is to evaluate the grade of WA vitrified and resinoid bond grinding wheels by the sue of AE measuring system. When the manufactured 48 kinds of specimens were scratched by the method of OKOSHI'S grade test, the relationship between the amount of bit scratch depth of grinding wheel specimens and the character- istics of AE signals, and the relationship of AE counts and grade were considered as fololws; (1) The higher the grades are AE cumlulative event counts N and AE event count rate n, the smaller the values tend to be. But A $E_{rms}$is in reverse. (2) In the case of same grade, the smaller the grain size is, the higher the value of AE cumulative event counts N and A $E_{rms}$is results of comparison and observation. The grinding wheel with lower elasticity and with higher percentage of pore detected higher value of AE cumula- tive event counts N than with higher elasticity and lower percentage of pore. But A $E_{rms}$ is in reverse. (3) AE cumulative event counts N and bit scratch depth h have normally one to one correspondence. (4) It can be expected that quantitative evaluations of grade by using AE have been carried out by the wave observation of AE signal in line with the relationship between load speed of bit and AE cumulative event counts N & AE event count rate n.' AE event count rate n.ate n.

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Effects of Initial AE Counts During Plastic Deformation in Friction \elding of Dissimilar Steel Tubes on the Weld Quality Control (이종강관 마찰용접의 소성변형 중 발생된 초기 AE양이 용접품질 제어에 미치는 영향에 관한 연구)

  • 오세규;김동조;정락기
    • Journal of Welding and Joining
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    • v.1 no.2
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    • pp.69-75
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    • 1983
  • Both in-process quality control and reliability of the weld is one of the major concerns is applying friction welding. No reliable nondestructive monitoring method is available at present to determine the weld quality particularly in process of production. So that, this paper presents an experimental examination and quantitative analysis for the effects of initial acoustic emission(AE) counts on the weld strength relating to the rotating speed as a new approach which attempts finally to develop an on-line quality monitoring system design for friction welds using AE techniques. As one of the important results, it was well confirmed that the initial AE counts occurring during plastic deformation period of welding were quantitatively correlated with reliability at 95% confidence level to the joint strength of welds, tube-to-tube (SM 20 C to STS 304) and then an AE technique using the initial AE counts can be reliably applied to in-process strength monitoring of the weld.

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Friction Welding Optimization of Elevated Temperature Materials for Pressure Vessels and Its Quality Evaluation by AE (압력용기용 고온재료의 마찰용접 최적화 및 AE에 의한 실시간 품질평가( I ))

  • 김헌경;공유식;이연탁;유인종;오세규
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2001.05a
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    • pp.301-306
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    • 2001
  • In this paper, friction welding optimization for 1Cr0.5Mo to STS304 and AE applications for the weld quality evaluation were investigated The important results of this study are as follows : 1. The techiques for dissimilar friction welding optimization if the elevated temperature materials 1Cr0.5Mo and STS304 and its real-time weld quality evaluation by AE were developed, considering on both strength and toughness. 2. Quantitative relationship was identified among welding condition, weld quality and cumulative AE counts.

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Characterization of Stress Corrosion Cracking at the Welded Region of High Strength Steel using Acoustic Emission Method (음향방출법에 의한 고 장력강 용접부의 부식손상 특성 평가)

  • Na, Eui-Gyun;Kim, Hoon
    • Journal of the Korean Society for Nondestructive Testing
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    • v.23 no.3
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    • pp.212-219
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    • 2003
  • This study is to evaluate the characteristics of SCC at the welded region of high strength steel using acoustic emission(AE) method. Specimens were loaded by a slow strain rate method in synthetic seawater and the damage process was monitored simultaneously by AE method. Corrosive environment was controlled using the potentiostat, in which -0.8V and -1.1V were applied to the specimens. In the case of one-pass weldment subjected to -0.8V, much more AE counts were detected compared with the PWHT specimen. It was verified through the cumulative counts that coalescence of micro cracks and cracks for the one pass weldment with -0.8V were mostly detected. In case of the one pass weldment subjected to -1.1V, time to failure became shorter and AE counts were produced considerably as compared with that of the two pass weldment. It was shown that AE counts and range of AE amplitude have close relations with the number and size as well as width of the cracks which were formed during the SCC.

A Study on the AE Characteristics of the Carbon Fiber Composite Material (탄소섬유 복합재료의 AE 특성에 관한 연구)

  • 옹장우;이영신;심봉식;지용관;주영상
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.1
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    • pp.105-114
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    • 1989
  • This study was carried out to measure the mechanical properties and the acoustic emission (AE) characteristics of the carbon fiber reinforced composites of several types of the stacking sequence. AE signals were detected during the tensile tests. The number of ringdown counts, total ringdown counts were plotted together with the load-displacement curves. The tensile load-displacement behavior of specimen is compared and discussed based on the measured AE properties in relation to the failure mechanism. With the increase of load, AE signals increased. This showed that failure had being propagated by matrix deformation and cracking, delamination, fiber debonding and breakage. Felicity ratio has been obtained by observation of ;the Kaiser effect according to the variation of load ratio. The reloading tests showed that the felicity ratio decreased obviously when the load ratio or damage increased. These AE characteristics are hopeful to be employed as the criteria to evaluate the failure processes of composites.

Damage characterization of hard-brittle rocks under cyclic loading based on energy dissipation and acoustic emission characteristics

  • Li, Cheng J.;Lou, Pei J.;Xu, Ying
    • Geomechanics and Engineering
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    • v.31 no.4
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    • pp.365-373
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    • 2022
  • In order to investigate the damage evolution law of rock specimens under cyclic loading, cyclic loading tests under constant loads with different amplitudes were carried out on limestone specimens with high strength and brittleness values using acoustic emission (AE) technology and the energy evolution and AE characteristics were evaluated. Based on dissipated energy density and AE counts, the damage variable of specimen was characterized and two damage evolution processes were analyzed and compared. The obtained results showed that the change of AE counts was closely related to radial deformation. Higher cyclic loading values result in more significant radial strain of limestone specimen and larger accumulative AE counts of cyclic loading segment, which indicated Felicity effect. Regarding dissipated energy density, the damage of limestone specimen was defined without considering the influence of radial deformation, which made the damage value of cyclic loading segment higher at lower amplitude loads. The damage of cyclic loading segment was increased with the magnitude of load. When dissipated energy density was applied to define damage, the damage value at unloading segment was smaller than that of AE counts. Under higher cyclic loading values, rocks show obvious damage during both loading and unloading processes. Therefore, during deep rock excavation, the damages caused by the deformation recovery of unloading rocks could not be ignored when considering the damage caused by abutment pressure.

Evaluation on Creep Life Prediction of Aircraft Gas Turbine Material by AE (음향방출법에 의한 항공기용 가스터빈 재료의 크리프 수명예측 평가)

  • Kong, Y.S.;Yoon, H.K.;Oh, S.K.
    • Journal of Power System Engineering
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    • v.6 no.1
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    • pp.55-60
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    • 2002
  • There has been no report on the life prediction for gas turbine materials at high temperatures based on the creep properties and their relationship with the AE(acoustic emission) properties as a means of real-time non-destructive testing. One of the important issues is thus to develop a reliable method of evaluating creep properties by the AE technique. In this paper, the real-time evaluation of high temperature creep time and AE cumulative counts for nickel-based superalloy Udimet 720 was performed on round-bar type specimens under pure load at the temperatures of 811, 922 and 977K. The total AE cumulative counts until the starting point of secondary creep($N_1$) and that of tertiary creep($N_2$) have quantitative relationship with the tertiary creep time and the rupture time. It is thus possible to construct the life prediction system based on creep and the prevention system of tertiary creep by using AE technique.

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An Investigation of Fracture Mechanism of Spheroidal Graphite Cast Iron by Acoustic Emission Method (AE방법에 의한 구상화흑연(球狀化黑鉛) 주철재의 파괴기구 구명(究明))

  • Kim, S.C.;Ham, K.C.;Oh, B.S.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.6 no.2
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    • pp.17-36
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    • 1987
  • In this experimental research, fracture mechanisms of spheroidal graphite cast iron (As Cast, annealed and normalized) were investigated by using Acoustic Emission (AE) technique. In this study, the data (AE signal) are digitized and processed with the 8 bits micro-computer (APPLE II) connected to the AE measuring device without data processing unit. The source of AE signal was estimated by fractography analysis. The results obtained in this experimental study are summarized as follows : For the heterogeneous materials (spheroidal graphite cast iron) with inclusions which may considered as cracks, it is found that low and high AE amplitude appear simultaneously and the load is found to be fluctuated in the final stage of deformation. But the lad is not fluctuated in tension test with low AE amplitude only. AE is measured within elastic region and it is confirmed that 0.2% offset yield load agrees approximately with the load point where AE counts decrease steeply after the point of maximum AE counts.

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Evaluation of Fracture Behavior of High Tension Steel by AE Amplitude Distribution (AE 진폭분포를 이용한 고장력강의 파괴특성평가)

  • Seo, Jeong-Won;Seok, Chang-Seong;Kim, Yeong-Jin;Park, Ji-U
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.5 s.98
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    • pp.175-185
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    • 1999
  • Acoustic emission(AE) measurement was carried out to evaluate the fracture behavior of high tension steel. Fracture toughness $K_{AE}$ could be determined reasonably by using the load value corresponding to an abrupt change of the accumulated AE counts AE emitted from the test specimens. AE characteristics of the base metal, the weld metal and the heat-affected zone could be distinguished using a constant value b which represented the AE amplitude distribution, Consequently the structure integrity can be evaluated by variation of the constant b at the load level. In addition it was found that AE signals due to crack growth have high amplitude but low rise time and duration.

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REAL-TIME QUALITY EVALUATION OF FRICTION WELDING OF MACHINE COMPONENTS BY ACOUSTIC EMISSION (음향방출법(AE)에 의한 기계요소재의 마찰용접 품질 실시간 평가)

  • SAE-KYOO OH
    • Proceedings of the KWS Conference
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    • 1995.10a
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    • pp.3-20
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    • 1995
  • Development of Real-Time Quality Evaluation of Friction Welding by Acousitc Emission : Report 1 ABSTRACT : According as the friction welding has been increasingly applied in manufacturing various machine components because of its significant economic and technical advantages, one of the important concerns is the reliable quality monitoring method for a good weld quality with both joint strength and toughness in the process of its production. However no reliable nondestructive test method is available at present to determine the weld quality particularly in process of production. So this paper presents an experimental examination and quantitative analysis for the real-time evaluation of friction weld quality by acoustic emission, as a new approach which attempts finally to develop an on-line quality monitoring system design for friction welds using AE techniques. As one of the important results, it was confirmed, through this study, that AE techniques can be reliably applied to evaluating the friction weld qualify with 100% joint strength, as the cumulative AE counts occurring during welding period were quantitatively correlated with reliability at 95% confidence level to the joint strength of welds. Real-Time Evaluation of Automatic Production Quality Control for Friction Welding Machine : Report 2 Abstract : Both in-process quality control and high reliability of the weld is one of the major concerns in applying friction welding to the economical and qualified mass-production. No reliable nondestructive monitoring method is available at present to determine the real-time evaluation of automatic production quality control for friction welding machine. This paper, so that, presents the experimental examinations and statistical quantitative analysis of the correlation between the initial cumulative counts of acoustic emission(AE) occurring during plastic deformation period of the welding and the tensile strength of the welded joints as well as the various welding variables, as a new approach which attempts finally to develop an on-line (or real-time) quality monitoring system and a program for the process of real-time friction welding quality evaluation by initial AE cumulative counts. As one of the important results, it was well confirmed that the initial AE cumulative counts were quantitatively and cubically correlated with reliability of 95% confidence level to the joint strength of the welds, bar-to-bar (SCM4 to SUM31, SCM4 to SUM24L) and that an AE technique using initial AE counts can be reliably applied to real-time strength evaluation of the welded joints, and that such a program of the system was well developed resulting in practical possibility of real-time quality control more than 100% joint efficiency showing good weld with no micro-structural defects.

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