• Title/Summary/Keyword: 후방복사 프로파일

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Spectral Backward Radiation Profile (주파수 대역별 후방복사 프로파일)

  • Kim, Hak-Joon;Kwon, Sung-Duk
    • Journal of the Korean Society for Nondestructive Testing
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    • v.25 no.5
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    • pp.362-367
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    • 2005
  • Ultrasonic backward radiation profile is frequency-dependent when the incident region has deptional gradient of acoustical properties or multi-layers. Until now, we have measured the profiles of principal frequencies of an used transducers so that it was not easy to characterize the frequency dependence of the SAW(surface acoustic wave) from the backward radiation profile. We tried to measure the spectral backward radiation profiles using DFP(digital filer package) in a Lecroy DSO(digital storage oscilloscope). The measured spectral profiles showed that the steel specimen of #1200 surface treatment have 2% SAW velocity dispersion of the loaded case and the severly rusty steel specimen have the very big changes in the shape and pattern of the spectral profile. It is concluded that the spectral backward radiation profiles could be very effective tool to evaluate the frequency dependence of surface area.

Ultrasonic Backscattering Profiles from Zirconium Plate with Beryllium Diffusion Layer (베릴륨 표면확산 층을 가진 지르코늄 판재에서의 후방산란 프로파일)

  • Hwang, Y.H.;Choi, H.O.;Park, C.H.;Lee, Y.H.;Kwon, S.D.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.23 no.4
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    • pp.342-348
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    • 2003
  • Ultrasonic backscattering profiles of the Zr plates(with a thickness of 1.32mm) with/without Be-Zr alloy layer(with a thickness of $100{\mu}m$) were measured at various incidence positions to evaluate the characteristics of Be diffusion layer. Four principal subprofiles were observed in the backward ultrasound radiated from leaky Lamb waves. The angles and the intensities of the subprofile peaks decreased by the stiffening effect of Be layer. Generation and change of the subprofiles were explained by the acoustical property, collective group velocity and leaky factor difference of the plates under consideration. Backward radiation subprofiles turned out to be an useful method for evaluating thin diffusion layers on plates.

Effect of Surface Flaw Type on Ultrasonic Backscattering Profile (표면결함유형이 초음파 후방산란 프로파일에 미치는 영향)

  • Kwon, Sung-D.;Yoon, Seok-S.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.21 no.6
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    • pp.658-662
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    • 2001
  • The classification of surface flaw types was performed on the basis of angular dependence of backscattered ultrasound. The copper line adhered on the surface, cower line filled in groove, pure groove and the normal edge were adopted as various surface flaw patterns of glass specimen. A backward longitudinal profile was formed probably by the longitudinal wane scattering at and near 1st critical angle. The wave trains at the peak angles of the backward radiation profiles showed different shapes according to the superposition ratio of scattered and leaky waves. The asymmetry of the backward radiation profile arose due to the scattering effect of flaw. The additive resonance effect of copper line appeared in the left side of the profile. The peak angles of both the longitudinal and radiation profiles were shifted toward small angle by the scattering effect.

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Ultrasonic Backward Radiation on Randomly Rough Surface (무작위로 거친 표면에서의 후방복사 초음파)

  • Kwon, Sung-D.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.25 no.1
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    • pp.9-14
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    • 2005
  • The angular dependence(profile) of backward radiated ultrasound was measured for glass specimens with random surface roughness using ultrasonic goniometer that ran changes the incident angle continuously. It was concluded that the roughened region had greater acoustic impedance than the unperturbed region. The comparison of backward radiations showed that the amplitude of peak and the area of radiation profile were increased with surface roughness. It was suggested from the sensitive dependence of the profile area that the profile of backward radiation could be applied to in the nondestructive evaluation of sulfate region. Inclined C-scan technique with the transducer inclined at Rayleigh angle showed the reverse of luminosity and the high signal to noise ratio so that it provided high resolution.

Effects of Rubber Loading on the Ultrasonic Backward Radiation Profile of Leaky Lamb Wave (고무 접합이 후방복사된 리키 램파 프로파일에 미치는 영향)

  • Song, Sung-Jin;Kwon, Sung-Duk;Jung, Min-Ho;Kim, Young-H.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.22 no.5
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    • pp.508-515
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    • 2002
  • The characterization of adhesive property in multi-layer materials has been hot issue for a long time. In order to evaluate adhesive properties, we constructed fully automated system for the backward radiation of leaky Lamb wave. The backward radiation profiles were obtained for the bare steel plate and plates with rubber-loading. The rf waveforms and frequency spectra of backward radiation show the characteristics of involved leaky Lamb wave modes. As the thickness of rubber-loading increased, the amplitude of profile at the incident angle of $13.4^{\circ}$ exponentially decreased. Scanning the incident position over the partially rubber-loaded specimen shows good agreement with the actual rubber-loading. The backward radiation of leaky Lamb wave has great potential to evaluate the adhesive condition as well as material properties of plates.

Ultrasonic Backscattering on Painted Rough Surface at near Rayleigh Angle (레일리각 근처에서 도색된 거친 표면으로부터 후방 산란된 초음파)

  • Kwon, Sung-D.;Kwon, Yong-G.;Yoon, Seok-S.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.24 no.1
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    • pp.1-7
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    • 2004
  • The angular dependence (or profile) of backscattered ultrasound was measured for steel specimens with a range of surface roughness, $1{\sim}71{\mu}m$. Backscattering profiles at or near the Rayleigh angle still showed roughness dependence while the assessment of surface roughness via normal profile became impossible due to the paint layer masking the roughness. The peak amplitude directly radiated at the Rayleigh angle was proportional to the surface roughness, while the averaged peak amplitude radiated from the backward propagating Rayleigh wave, produced by reflection at a corner, was inversely proportional. In the painted specimens, the linearity of direct backward radiation with the roughness was observed even at the roughness of less than three hundredths of a wavelength, and the abnormal multiple bark reflection caused by periodic roughness disappeared.

Characterization of TiN Layered Substrate using Leaky Rayleigh Surface Wave (누설 레일리 표면파를 이용한 TiN 코팅 부재의 특성평가)

  • Kwon, Sung-Duk;Kim, Hak-Joon;Song, Sung-Jin
    • Journal of the Korean Society for Nondestructive Testing
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    • v.26 no.1
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    • pp.7-11
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    • 2006
  • Since ceramic layers coated on machinery components inevitably experience the changes in their properties it is necessary to evaluate the characteristics of ceramic coating layers nondestructively for a reliable use of coated components and 4heir remaining life prediction. To address such a need, in the present study, an ultrasonic backward radiation technique is applied to investigate the characteristics of leaky Rayleigh surface waves propagating through the very thin TiN ceramic layers coated on AISI 1045 steel or austenitic 304 steel substrate with three different conditions of surface roughness, coating layer thickness and wear condition. In the experiments performed in the present work, the peak angle and the peak amplitude of ultrasonic backward radiation profile varied sensitively according to three specimen preparation renditions. in fact, this result demonstrates a high possibility of the ultrasonic backward radiation as an effective tool for the nondestructive characterization of the resting layers even in such a thin regime.

Assessment of Degradation by Corrosion Fatigue of TMCP Steel using a Backward Radiated Ultrasound (후방복사 초음파를 이용한 TMCP강의 부식피로 손상평가)

  • Kim, Y.H.;Bae, D.H.;Park, J.H.;Yu, H.J.;Kwon, S.D.;Song, S.J.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.23 no.4
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    • pp.349-355
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    • 2003
  • Material degradation due to corrosion fatigue was evaluated nondestructively using backward radiated Rayleigh surface wave. h corrosion fatigue test was carried out for the specimens made of thermo-mechanically controlled process steel in 3.5wt.% NaCl solution at $25^{\circ}C$. The backward radiation profile, which is the amplitude variation of backward radiated ultrasound according to the incident angle, of the specimens were measured in water at room temperature after the corrosion fatigue test. The velocity of Rayleigh surface wave, determined from the incident angle at which the profile of the backward radiated ultrasound became maximum, decreased for the specimen that had the large number of cycles to failure in the corrosion fatigue test. This fact implies that the corrosion degradation occurred at specimen surface in this specific test is dominantly dependant on the me exposed to corrosion environment. The result observed in the present work demonstrates the high potential of backward radiated Rayleigh surface wave as a tool for nondestructive evaluation of corrosion degradation of aged materials.

Evaluation of Corrosion Fatigue Characteristics of 12Cr Steel Using Backward Radiated Ultrasound (후방복사된 초음파를 이용한 12Cr강 부식 피로특성 평가)

  • Kwon, Sung-Duk;Yoon, Seok-Soo;Song, Sung-Jin;Bae, Dong-Ho
    • Journal of the Korean Society for Nondestructive Testing
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    • v.20 no.5
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    • pp.397-401
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    • 2000
  • The corrosion-fatigue characteristics of the 12Cr steel, which is widely used in fossil power plants as a turbine blade material, are evaluated nondestructively by use of the Rayleigh surface wave. In this study, the frequency dependency of the Rayleigh surface wave is investigated indirectly by measuring the angular dependency of the backward radiation of the incident ultrasonic wave in the aged specimens, and then compared to the corrosion-fatigue characteristics. The width of the backward radiation profile decreases as the increase of the aging temperature, which seems to result from the increase of the effective degrading layer thickness. This parameter also shows an inversely proportionality to the exponent, m, in the Paris law which predicts the crack size increasement due to fatigue. The result observed in this study demonstrates high potential of the backward radiated ultrasound as a tool for the nondestructive evaluation of the corrosion-fatigue characteristics of the aged materials.

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Evaluation of Abrasive Wear Face Using SAW (표면탄성파를 이용한 마모 표면부의 평가)

  • Kwon, Sung-D.;Yoon, Seok-S.;Song, Sung-J.;Lee, Young-Z.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.22 no.2
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    • pp.193-197
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    • 2002
  • The frequency dependency of the Rayleigh surface wave was investigated indirectly by measuring the angular dependency of the backward radiation of the incident ultrasonic wave in the abrasion specimens, which was explained in view of the residual stress distribution. The peak intensity of the backward radiation profile decreased and the right half width of the profile increased with an increase of the variational rate of residual stress for the scuffing specimen. The peak intensity was also affected by the surface wave scattering during the propagation around the micro-damages. The peak angle might depend on not only the amount of residual stress but also the micro-structure. The result observed in this study demonstrates the high potential of the backward radiated ultrasound as a tool for the nondestructive evaluation of the subsurface gradients of materials.