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Scattering of elastic waves by non-planar cracks
ND T Abstracts The ultrasonic wave propagationcharacteristicswere ~ u r o d for IN100, a powder metallurgy alloy used for aircraft engine components.This material was selected as a model system for testing the feasibility of characterizing the microslructure of a variety of inhomogeueousmedia including powder metals, ceramics,castings and composites.The datawere obtained for a frequency range from about 2 to 20 MHz and were statistically averaged over numerous volume elements of the samples. Micrographical examination provided size and number dislributions for grain and pore structure. The results showedthat the predominantsourcefor the ultrasonic attenuation and backscatter was a dense (approx. 100/ram) disUibution of small micropores (approx. 10 microns radius). Two samples with different micropore densities were studied in detail to test the feasihility of calculating from observed microstrnctural parameters the frequency dependenceof the microstrnctural hackscatter in the regime for which the wavelength is much larger than the size of the individual scattering centers. 36784 Telschow, K I..; Flinn, J.E. Ultrasonic backscatter and attenuation
measurements
for
microstructure characterization: application to consolidated rapidly solidified type 304 stainless steel powder Idaho National Engineering Laboratory, Idaho (United States), EGG-SCM- 7198, DE86-014917, 41 pp. (Mar. 1986) The results of this study show that ultrasonic measurements of attenuation and hackscatter energy can be correlated with microstructural features in the RSP consolidated materials utilized. In particular, attenuation and backscatter energy were shown to be consistent with each other and to yield approximately the same microstructurni information. This is important because the buckscatter technique can be implemented more easily than the attenuation measurement as it requires access to only one surface of the sample under study. More information is available in the backscatter signals, but as yet is not understood well enough to be utilized. The high degree of correlation between the microstructural examinations and the ultrasonic measurements allows the latter to be of use in evaluating the effectiveness of various consolidation methods. 36777 Miller, J.G. Quantitative non-destructive evaluation of damage in composite materials using transmitted and reflected ultrasound Washington University, St. Louis, Missouri (United States), N85-21269, 40 pp. (1985) The application of ultrasound for the nondestructive evaluation of advanced composite materials is summarized. Quantitative indices from fundamental acoustic parameters of the inhomogeneous malmials were derived. The investigations into the estimation of the average attcauation from backscatteredultrasoundare described.The use of a centroid.shift
techniquein inhomogeneonsmaterialsis reportedand investigation into the use of the Wigner distribution for attenuation estimation is summarized.
36557 Bostrom, A.; Olsson, P. Scattering of elastic waves by non-planar cracks Wave Motion, Vol. 9, No. I, pp. 61-76 (Jan. 1987) A modificationof the nullfieldapproach is used to study the scattering of elastic waves by non-planar cracks. A fictitious surface is added to the crack so that a convenientclosed surface is obtained and the surface fields on this dosed surfaceare expandedin vector sphericalharmonics.The edge conditions are introduced into these expansionsand this is shown to be essential for the numerical convergence. Total cross sections and b~kscattering amplitudes as functions of frequency are computed numerically for rotationally symmeaic cracks which are part of sphericalor spheroidal surfaces. By integration in frequency backscattered pulses are also computed.Somecaseswith two cracks are also considered. 36522 Buoncn'stiani,A.M.; Smith, B.T. Backscatter of acoustic signals from inhomogeneities in composites IEEE 1985 Ultrasonics Symposium, San Francisco, California (United States), 16-18 Oct. 1985, pp. 1068-1071. Edited by B.R. McAvoy. IEEE, Piscataway, New Jersey 0985) We have developed a simple, effective method for analyzing the transmission aad reflection of acoustic signals from the bulk of a composite material. Using a one-dimensional invariant embedding argument, we derive two coupled recorsion relations for the reflection and transmission coefficients and a non-linear identity between them. 36470 Saniie, J.; Bilgutay, N.M. Quantitative grain size evaluation using ultrasonic backscattered echoes Journal of Acoustical Society of America, Vol. 80, No. 6, pp. 18161824 (Dec. 1986) Grain size characterization using ultrasonic hack~c~_!tezedsignals is an important problem in nondestructive testing of materials. In this paper, a heuristic model which relates the statisticni clmrscamstics of the memured signal to the mean ultrasonicwavelet and atwamation coeffic~t in different regions of the sample is investigated. The losses in the t~_ t-~m.xed signal are examined using temporal averaging, correlation, and pmb~lity distribution functions of the segmented data. Farthetmore, homom0rl~ic processing is used in a novel application to estimate the mean ultrasonic wavelet (as it propagates through the sample) and the ftexl~,,ncy-dependent attenuation. In the work presented, heat-treateA stainless steel samples with various grain sizes am examined. The processed experiment~ results support the feasibility of the grain size evaluation techniques presented here using the hackscattered grain signal.
Each entry in NDT Abstracts consists of the serial number in the National NDT Centre Information Store for identification purposes; the title of the paper, book or report; the name of the author; the name of the source journal or document and the abstracts. Where necessary, author's names and the title of foreign journals have been transliterated into the Latin alphabet according to British Standard BS 2979 : 1958.
Information Service, US Department of Commerce, Springfield, Virginia 22151, USA. British and foreign standards can be obtained from Sales Department, British Standards Institution, I01 Pentonville Road, London N1 9ND; and British and foreign patents from the Patents Office Sales Branch, Block C, Station Square House, St Mary Cray, Orpington, Kent BR5 3RD.
Availability of Publications
Information-retrieval Service
Most papers listed may be obtained as loans or copies via local library or direct from Loans Department, British Library Document Supply Centre, Boston Spa, Wetherby, Yorkshire LS23 7BQ. Details of the British Lending Library's UK and International Services may be obtained from The Director, British Library Lending Division. Technical reports are also available from the Loans Department of the British Lending Library and in the USA from the National Technical
272
NDT&E
I n t e r n a t i o n a l V o l u m e 26 N u m b e r 5 1 9 9 3
All entries are indexed in a computerized retrieval system, located at Harwell, which allows rapid searching of information relevant to any particular inspection problem~ This service is available to both UK and overseas organizations through the National NDT Centre's Qualtis Subscription Scheme - further details are available from Phil Lawrence on Abingdon (0235) 433391.
© 1993 United Kingdom Atomic Energy Authority
measurements
for
microstructure characterization: application to consolidated rapidly solidified type 304 stainless steel powder Idaho National Engineering Laboratory, Idaho (United States), EGG-SCM- 7198, DE86-014917, 41 pp. (Mar. 1986) The results of this study show that ultrasonic measurements of attenuation and hackscatter energy can be correlated with microstructural features in the RSP consolidated materials utilized. In particular, attenuation and backscatter energy were shown to be consistent with each other and to yield approximately the same microstructurni information. This is important because the buckscatter technique can be implemented more easily than the attenuation measurement as it requires access to only one surface of the sample under study. More information is available in the backscatter signals, but as yet is not understood well enough to be utilized. The high degree of correlation between the microstructural examinations and the ultrasonic measurements allows the latter to be of use in evaluating the effectiveness of various consolidation methods. 36777 Miller, J.G. Quantitative non-destructive evaluation of damage in composite materials using transmitted and reflected ultrasound Washington University, St. Louis, Missouri (United States), N85-21269, 40 pp. (1985) The application of ultrasound for the nondestructive evaluation of advanced composite materials is summarized. Quantitative indices from fundamental acoustic parameters of the inhomogeneous malmials were derived. The investigations into the estimation of the average attcauation from backscatteredultrasoundare described.The use of a centroid.shift
techniquein inhomogeneonsmaterialsis reportedand investigation into the use of the Wigner distribution for attenuation estimation is summarized.
36557 Bostrom, A.; Olsson, P. Scattering of elastic waves by non-planar cracks Wave Motion, Vol. 9, No. I, pp. 61-76 (Jan. 1987) A modificationof the nullfieldapproach is used to study the scattering of elastic waves by non-planar cracks. A fictitious surface is added to the crack so that a convenientclosed surface is obtained and the surface fields on this dosed surfaceare expandedin vector sphericalharmonics.The edge conditions are introduced into these expansionsand this is shown to be essential for the numerical convergence. Total cross sections and b~kscattering amplitudes as functions of frequency are computed numerically for rotationally symmeaic cracks which are part of sphericalor spheroidal surfaces. By integration in frequency backscattered pulses are also computed.Somecaseswith two cracks are also considered. 36522 Buoncn'stiani,A.M.; Smith, B.T. Backscatter of acoustic signals from inhomogeneities in composites IEEE 1985 Ultrasonics Symposium, San Francisco, California (United States), 16-18 Oct. 1985, pp. 1068-1071. Edited by B.R. McAvoy. IEEE, Piscataway, New Jersey 0985) We have developed a simple, effective method for analyzing the transmission aad reflection of acoustic signals from the bulk of a composite material. Using a one-dimensional invariant embedding argument, we derive two coupled recorsion relations for the reflection and transmission coefficients and a non-linear identity between them. 36470 Saniie, J.; Bilgutay, N.M. Quantitative grain size evaluation using ultrasonic backscattered echoes Journal of Acoustical Society of America, Vol. 80, No. 6, pp. 18161824 (Dec. 1986) Grain size characterization using ultrasonic hack~c~_!tezedsignals is an important problem in nondestructive testing of materials. In this paper, a heuristic model which relates the statisticni clmrscamstics of the memured signal to the mean ultrasonicwavelet and atwamation coeffic~t in different regions of the sample is investigated. The losses in the t~_ t-~m.xed signal are examined using temporal averaging, correlation, and pmb~lity distribution functions of the segmented data. Farthetmore, homom0rl~ic processing is used in a novel application to estimate the mean ultrasonic wavelet (as it propagates through the sample) and the ftexl~,,ncy-dependent attenuation. In the work presented, heat-treateA stainless steel samples with various grain sizes am examined. The processed experiment~ results support the feasibility of the grain size evaluation techniques presented here using the hackscattered grain signal.
Each entry in NDT Abstracts consists of the serial number in the National NDT Centre Information Store for identification purposes; the title of the paper, book or report; the name of the author; the name of the source journal or document and the abstracts. Where necessary, author's names and the title of foreign journals have been transliterated into the Latin alphabet according to British Standard BS 2979 : 1958.
Information Service, US Department of Commerce, Springfield, Virginia 22151, USA. British and foreign standards can be obtained from Sales Department, British Standards Institution, I01 Pentonville Road, London N1 9ND; and British and foreign patents from the Patents Office Sales Branch, Block C, Station Square House, St Mary Cray, Orpington, Kent BR5 3RD.
Availability of Publications
Information-retrieval Service
Most papers listed may be obtained as loans or copies via local library or direct from Loans Department, British Library Document Supply Centre, Boston Spa, Wetherby, Yorkshire LS23 7BQ. Details of the British Lending Library's UK and International Services may be obtained from The Director, British Library Lending Division. Technical reports are also available from the Loans Department of the British Lending Library and in the USA from the National Technical
272
NDT&E
I n t e r n a t i o n a l V o l u m e 26 N u m b e r 5 1 9 9 3
All entries are indexed in a computerized retrieval system, located at Harwell, which allows rapid searching of information relevant to any particular inspection problem~ This service is available to both UK and overseas organizations through the National NDT Centre's Qualtis Subscription Scheme - further details are available from Phil Lawrence on Abingdon (0235) 433391.
© 1993 United Kingdom Atomic Energy Authority