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Characterization of composite laminates using combined LLW and PBS methods
ND T Abstracts This paper addresses the inverse acoustic scattering problem as it pertains to nondestructive evaluation (NDE) by acoustic means. Our emphasis is on the formulation of scattering phenomena based on the joint time and frequency representation of the scattering response function. The inverse scattering model presented here deals with a spherically shaped, isotropic-elastic object insonified by a plane wave. A single receiving sensor is placed in the backscatter direction. The main objective of this study is to determine the extent to which the physical ~ e t e r s associated with this scatterer, e.g. size and elastic constants (longitudinal and shear sound velocities), can be determined from data obtained with a single receiving sensor,
48631 Ramabadran, T.V.; Yoon, M.-H. Deconvolution of ultrasonic backscattered signals using the K a i m a n filter Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 15-20 Jul. 1990. Vol. 10A, pp. 733-740. Edited by D.O, Thompson, and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4. In this paper, we investigate the use of an aigorithm based on the Kaiman filter. Such an algorithm has been applied previously for tissue characterization and seismic data processing. The main advantage of the Kalmnn filter approach is that it can be more readily applied to situations involving time-varying signals and/or nonstationary statistics and consequently has the potential to perform better under these situations.In the following, we first describe the deconvolution algorithm based on the Kalman filter and then present a few examples of its application. 48628 Karpur, P.; Resch, M.T. Improved detectability of fatigue microcracks by spit spectrum processing of hackscattered Rayleigh waves Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 15-20 Jui. 1990. Vol. 10A, pp. 757-764. Edited by D.O. Thompson, and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4. The reason for developing new techniques to detect and measure the size of surface microcracks is that, in the so called small crack size regime small cracks have been observed to grow at rates which are orders of magnitude higher than large sized cracks when subjected to identical magnitudes of crack driving force. Cracks as small as 70 micrometer radius (halfpenny shape) initiated due to fatigue, can be detected using Rayleigh waves. Split spectrum processing has been shown here to be an effective tool for the enhancement of SNR when the reflector of interest is many times smaller that the wavelength of interrogating ultrasound. Microcracks as small as 113 micrometers have been detected without processing and 20 micrometers with processing. There is still a long way to go because it is necessary to develop basis for the selection of the processing parameters when the reflector is in a 'small-reflector' regime.
48440
Willeras, H.
Nondestructive determination of h a r d e n i n g depth in induction hardened components by ultrasonic b a c k l ~ t t e r i n g Review of Progress in Quantitative Nondesu'uctive Evaluation, La Jolla, California (United States), 15-20 Jul. 1990. Vol. 10B, pp. 1707-1713. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4 Induction hardening is a well established technique to improve the resistance of components like bearings, gears, rolls etc. a t,aimt loading and to protect the surface against wear. The determination of the hardening depth according to its definition is only possible in a destructive way using standardization measuring procedures (Vickers, Rockwell, etc). As the destructive measurements, besides being time consumingand expensive, are limited to spot checks, there is a strong industrial need for nondeslructive determination of hardening depth. It has been demonslrated that the ultrasonic backscattering technique is an appropriate tool for measuring hardening depth in induction hardened components, which have transition zones of negligible extension. Under these conditions, hardening depths in the range 2 -> 12 mm can be determined with an accuracy of better than + 10%. Because the thickness of the hardened zone is directly evahmted from an ultrasonic lime-of-flight measurement, no special calibration procedure is required. The prototype system available allows fully automated determination of hardening depth. Its use under practical conditions has already been demonstrated.
48439 Rose, J.H. Ultrasonic backscattering from polycrystailine aggregates using time. domain linear response theory Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 15-20 Jul. 1990. Vol. 10B, pp. 1715-1720. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4
264
N D T & E International Volume 26 Number 5 1993
The ultrasonic detection of altered microstructures in metals is a difficult, but necessary task. The detection of hard alpha inclusions in titauium jet engine disks is an important, safety related, example of the need. One proposed tool for detecting such altered microstructures involves analyzing changes in the ultrasonic grain noise; i.e., in the incoherent part of the scattered signal. In this progress report, we develop a quantitative, computable and accurate formalism that determines the backscattered acoustic signal from the microstructure of a polycrystalline aggregate. We fwst define our experiment. Next we use Auid's form of the reciprocity relation (reexpressed in terms of volume integrals and in the time domain) to express the acoustic signal in terms of the material properties of the aggregate. Computable expressions are obtained from the general result by making a varietyof realistic assumptions. These computable expressions are then shown to yield a simple inversion formula for the fluctuations in the acoustic impedance of the aggregate, given the measured acoustic signal. 48438 Margetan, FJ.; Gray, T.A.; Thompson, R~B. A technique for quantitative measuring microstructurally induced ultrasonic noise Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 15-20 Jul. 1990. Vol. 10B, pp. 1721-1728. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4 In ultrasonic inspections of aircraft engine components, the detectability of critical defects can be limited by grain noise. A sound quantitative description of grain noise in such alloys is essential for accurate estimates of flaw detection reliability. In this work we present a method for quantifying backscatternd grain noise by using positioned averaging to determine the ront-mean-sqmued (nns) noiselevel. The measured noise level will depend on details of the measurement systems as well as on inherent material properties of the alloy. We present a preliminary model of the noise measurement p ~ s which accounts for system effects, and we compare its predictions with experiment. We then indicate how the rms noise data can be processed to extract a factor which parametefizes the inherent noise severity independent of the measurement process.
48420 Bashyam, M. Ultrasonic NDE for ceramic- a n d metal matrix composite material characterization Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 15-20 Jul. 1990. Vol. 10B, pp. 1423-1430. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4. Our research focuses on characterizing one metai-matrix and two ceramic-matrix composites. Various type,s of defects were deliberamly introduced into these panels by the manufacturer, to simulate delamination, porosity, fiber breakage and matrix cracking etc. This paper discusses ultrasonic velocity, attenuation, baekseaUnr and surface wave techniques to characterize the internal structural features ofti~ MMC and CIVICmaterials.
48407 Bar-Cohen, Y.; Mal, A.K. Characterization of composite laminates using combined L L W and PBS methods Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 15-20 Jul. 1990. Vol. 10B, pp. 1555-1560. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4. Quantitative bIDE capability that has become available in recent years axe the leaky Lamb waves (LLW) and polar ~ n g (PBS). Significant progress has been made in receat years in t h e ~ analysis of the wave behavior in transversely isotmpic laye~.d media. These methods can be Used (a) in conjunction with a C-scan system to provide images of various type of defects, or Co)through various measurements to charueterize defects and determine the material elastic properties.Present work is directed toward combining the use of both LLW and PBS for ~ a l characterization.
48361 Gorman, M.R. Ultrasonic polar backscatter imaging of transverse matrix cracks Journal of Composite Materials, Vol. 25, No. 11, pp. 1499-1514 (Nov. 1991)
48631 Ramabadran, T.V.; Yoon, M.-H. Deconvolution of ultrasonic backscattered signals using the K a i m a n filter Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 15-20 Jul. 1990. Vol. 10A, pp. 733-740. Edited by D.O, Thompson, and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4. In this paper, we investigate the use of an aigorithm based on the Kaiman filter. Such an algorithm has been applied previously for tissue characterization and seismic data processing. The main advantage of the Kalmnn filter approach is that it can be more readily applied to situations involving time-varying signals and/or nonstationary statistics and consequently has the potential to perform better under these situations.In the following, we first describe the deconvolution algorithm based on the Kalman filter and then present a few examples of its application. 48628 Karpur, P.; Resch, M.T. Improved detectability of fatigue microcracks by spit spectrum processing of hackscattered Rayleigh waves Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 15-20 Jui. 1990. Vol. 10A, pp. 757-764. Edited by D.O. Thompson, and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4. The reason for developing new techniques to detect and measure the size of surface microcracks is that, in the so called small crack size regime small cracks have been observed to grow at rates which are orders of magnitude higher than large sized cracks when subjected to identical magnitudes of crack driving force. Cracks as small as 70 micrometer radius (halfpenny shape) initiated due to fatigue, can be detected using Rayleigh waves. Split spectrum processing has been shown here to be an effective tool for the enhancement of SNR when the reflector of interest is many times smaller that the wavelength of interrogating ultrasound. Microcracks as small as 113 micrometers have been detected without processing and 20 micrometers with processing. There is still a long way to go because it is necessary to develop basis for the selection of the processing parameters when the reflector is in a 'small-reflector' regime.
48440
Willeras, H.
Nondestructive determination of h a r d e n i n g depth in induction hardened components by ultrasonic b a c k l ~ t t e r i n g Review of Progress in Quantitative Nondesu'uctive Evaluation, La Jolla, California (United States), 15-20 Jul. 1990. Vol. 10B, pp. 1707-1713. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4 Induction hardening is a well established technique to improve the resistance of components like bearings, gears, rolls etc. a t,aimt loading and to protect the surface against wear. The determination of the hardening depth according to its definition is only possible in a destructive way using standardization measuring procedures (Vickers, Rockwell, etc). As the destructive measurements, besides being time consumingand expensive, are limited to spot checks, there is a strong industrial need for nondeslructive determination of hardening depth. It has been demonslrated that the ultrasonic backscattering technique is an appropriate tool for measuring hardening depth in induction hardened components, which have transition zones of negligible extension. Under these conditions, hardening depths in the range 2 -> 12 mm can be determined with an accuracy of better than + 10%. Because the thickness of the hardened zone is directly evahmted from an ultrasonic lime-of-flight measurement, no special calibration procedure is required. The prototype system available allows fully automated determination of hardening depth. Its use under practical conditions has already been demonstrated.
48439 Rose, J.H. Ultrasonic backscattering from polycrystailine aggregates using time. domain linear response theory Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 15-20 Jul. 1990. Vol. 10B, pp. 1715-1720. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4
264
N D T & E International Volume 26 Number 5 1993
The ultrasonic detection of altered microstructures in metals is a difficult, but necessary task. The detection of hard alpha inclusions in titauium jet engine disks is an important, safety related, example of the need. One proposed tool for detecting such altered microstructures involves analyzing changes in the ultrasonic grain noise; i.e., in the incoherent part of the scattered signal. In this progress report, we develop a quantitative, computable and accurate formalism that determines the backscattered acoustic signal from the microstructure of a polycrystalline aggregate. We fwst define our experiment. Next we use Auid's form of the reciprocity relation (reexpressed in terms of volume integrals and in the time domain) to express the acoustic signal in terms of the material properties of the aggregate. Computable expressions are obtained from the general result by making a varietyof realistic assumptions. These computable expressions are then shown to yield a simple inversion formula for the fluctuations in the acoustic impedance of the aggregate, given the measured acoustic signal. 48438 Margetan, FJ.; Gray, T.A.; Thompson, R~B. A technique for quantitative measuring microstructurally induced ultrasonic noise Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 15-20 Jul. 1990. Vol. 10B, pp. 1721-1728. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4 In ultrasonic inspections of aircraft engine components, the detectability of critical defects can be limited by grain noise. A sound quantitative description of grain noise in such alloys is essential for accurate estimates of flaw detection reliability. In this work we present a method for quantifying backscatternd grain noise by using positioned averaging to determine the ront-mean-sqmued (nns) noiselevel. The measured noise level will depend on details of the measurement systems as well as on inherent material properties of the alloy. We present a preliminary model of the noise measurement p ~ s which accounts for system effects, and we compare its predictions with experiment. We then indicate how the rms noise data can be processed to extract a factor which parametefizes the inherent noise severity independent of the measurement process.
48420 Bashyam, M. Ultrasonic NDE for ceramic- a n d metal matrix composite material characterization Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 15-20 Jul. 1990. Vol. 10B, pp. 1423-1430. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4. Our research focuses on characterizing one metai-matrix and two ceramic-matrix composites. Various type,s of defects were deliberamly introduced into these panels by the manufacturer, to simulate delamination, porosity, fiber breakage and matrix cracking etc. This paper discusses ultrasonic velocity, attenuation, baekseaUnr and surface wave techniques to characterize the internal structural features ofti~ MMC and CIVICmaterials.
48407 Bar-Cohen, Y.; Mal, A.K. Characterization of composite laminates using combined L L W and PBS methods Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 15-20 Jul. 1990. Vol. 10B, pp. 1555-1560. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4. Quantitative bIDE capability that has become available in recent years axe the leaky Lamb waves (LLW) and polar ~ n g (PBS). Significant progress has been made in receat years in t h e ~ analysis of the wave behavior in transversely isotmpic laye~.d media. These methods can be Used (a) in conjunction with a C-scan system to provide images of various type of defects, or Co)through various measurements to charueterize defects and determine the material elastic properties.Present work is directed toward combining the use of both LLW and PBS for ~ a l characterization.
48361 Gorman, M.R. Ultrasonic polar backscatter imaging of transverse matrix cracks Journal of Composite Materials, Vol. 25, No. 11, pp. 1499-1514 (Nov. 1991)