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41653 Screening of metal matrix composites using ultrasonic C-scans
Journal of Acoustic Emission, Vol. 8, Nos. 1-2, pp. 5314-5316 (Jan. Jun. 1989). Special Supplement - Extended Summaries of Papers to be presented at the World Meeting on Acoustic Emission, Charlotte, North Carolina, U S A , 20-23 Mar. 1989 A combination of two nondestructive techniques, acoustic emission and ultrasonics, is used to assess the structural performance of adhesively bonded joints in service. This study found good correlations between the acoustoultrasonic parameter (AUP) and the shear strength of the bonded joint in composites and steel, as well as between the AUP and the peel strength of the foam core aluminium panels. 41807
Kenurth, D.C.; Telschow, K.L.; Walter J.B.
Characterization of porosity distributions in advanced ceramics: a comparison of ultrasonic methods Materials Evaluation, Vol. 47, No. 5, pp. 571-575 (May 1989) This paper describes the characterization of an SiC sample that was intentionally processed to contain a distinctly nonuniform porosity distribution. The characterization was done with optical microscopy, radiography, and ultrasonic techniques, which recorded C-scan images of scatterer time of flight, backscatter energy, group velocity, and back- surface echo energy. All of the techniques delineated the porosity distribution in varying degrees and different ways, Significant modulation effects were observed in the back-surface echo-energy measurements because of the nonuniformity in the porosity distribution. This technique proved to be very sensitive to large spatial gradients in the porosity distributions. The velocity measurements were the most accurate in determining the local value of the porosity. These results demonstrate the usefulness of ultrasonic probes for porosity determination in materials with nonuniform spatial distributions. 41806
Cawley, P.; Adams, R.D.
Sensitivity of the coin-tap method of nondestructive testing Materials Evaluation, Vol. 47, No. 5, pp. 558-563 (May 1989) The sensitivity of an automated version of the coin-tap method of nondestructive testing has been investigated. The method has been used to produce C-scan presentations of the defect locations in sets of solid aluminum plates and carbon fiber-reinforced plastic (CFRP) honeycomb panels with deliberately introduced defects. The sensitivity of the method decreases with increasing defect depth, but it has been shown that its sensitivity is somewhat better than that of the mechanical impedance technique. A defect of 10 mm dia under a 1 mm thick CFRP skin is at the margin of detectability, compared with a defect of 20 mm dia using the impedance technique, ft has been shown also that the coin-tap test is more reliable on flexible structures than the mechanical impedance method. No couplant is required between the structure and the tapping head. 41795
Nonaka, T.; Hayakawa, Y.; Takeda, S.; Nishimori, H.
Ultrasonic imaging system for composites and ceramics Materials Evaluation, Vol. 47, No. 5, pp. 542,544-546 (May 1989) Several applications of ultrasonic (US) imaging and data-processing techniques for ceramics and composite materials are described. High frequency US tests can be used to measure very thin delaminations in composites and the very small flaws in ceramics. The system used includes an x-y-z scanner with a transducer, ultrasonic testing units, and a computer for control and data processing. 41784
Wooh, S.C.; Daniel, I.M.
Enhancement techniques for ultrasonic imaging of damage in composite materials New Directions in the Nondestructive Evaluation of Advanced Materials, Winter Annual Meeting, American Society of Mechanical Engineers, Chicago, Illinois, 27 Nov-2 Dec. 1988. Edited by J.L. Rose and A.A. Tseng, pp. 53-62. American Society of Mechanical Engineers (1988) Conventional ultrasonic C-scanning sometimes produces distorted and degraded images due to a variety of reasons, including surface roughness, beam dispersion, extraneous noise and imperfect fidelity of the total acquisition system, Enhancement techniques, using computer data acquisition and processing, can be used to enhance and restore the image. Enhancement techniques described include contrast stretching and median filtering, histogram equalization, thresholding, dynamic thresholding, thresholding depending on boundary characteristics, one- dimensional segmentation and intensity scans with hidden line removal. These enhancement techniques were applied and illustrated for five different types of damage in graphite/epoxy composite materials, embedded film patch in quasi-isotropic laminate, impact damage in quasi-isotropic laminate, matrix cracking due to static loading of crossply laminate, fatigue damage in crossply laminate, and thermally induced cracks in a thick crossply laminate. There is no single technique that is optimum in all cases. A suitable combination of techniques must be selected for optimum image quality. 41782
Kline, R.A.
Quantitative NDE of advanced composites using ultrasonic velocity measurements New Directions in the Nondestructive Evaluation of Advanced Materials, Winter Annual Meeting, American Society of Mechanical Engineers, Chicago, Illinois, 27 Nov-2 Dec. 1988. Edited by J.L. Rose and A . A . Tseng, pp. 35-40. American Society of Mechanical Engineers (1988)
NDT International August 1990
In this work, the use of ultrasonic velocity analysis for the quantitative nondestructive evaluation of the mechanical properties of composite laminates is discussed. The composite laminate is modeled as a layer or set of layers of transversely isotropic material of known orientation. The method described utilizes velocity measurements for ultrasonic wave propagation at multiple angles of incidence. Since the equations are algebraically cumbersome, a numerical procedure employing a commercially available nonlinear equation solving subroutine is utilized. Applications to composite laminates are presented. 41765
Clarke, W.G., Jr.; lyer, J.N.
Structure modeling and the nondestructive evaluation of metal-matrix composites Materials Evaluation, Vol. 47, No. 4, pp. 460-465 (Apr. 1989) Powder metallurgy and liquid mercury modeling techniques were used to replicate the microstructure of metal-matrix composite materials. These models, in turn, were used to establish eddy current and ultrasonic inspection signatures for a variety of structure variables. The impact of matrix chemistry, reinforcement type (shape, sizes, etc.), interface conditions, reinforcement loading, and material processing on nondestructive evaluation (NDE) response was established, These results provide guidelines for the analysis of relevant vs. nonrelevant inspection results as well as a basis for in-process NDE options. The experimental effort was directed specifically at the silicon carbine- reinforced aluminum system but the observations and conclusions are widely applicable to metal-matrix composites in general. 41755
Rogovsky, A.J.
Engineering selection of NDT techniques and accept/reject criteria for composites New Directions in the Nondestructive Evaluation of Advanced Materials, Winter Annual Meeting, American Society of Mechanical Engineers, Chicago, Illinois, 27 Nov-2 Dec. 1988. Edited by J.L. Rose and A.A. Tseng, pp. 45-52. American Society of Mechanical Engineers (1988) Several types of honeycomb and graphite-epoxy composites were investigated to determine appropriate techniques and accept/reject criteria for NDT. Samples with built-in defects of various types, sizes, and locations were designed and fabricated. Ultrasonic, infrared imaging, and x-ray techniques were applied for flaw detection, sizing and characterization. Composite samples with and without defects under-went thermocycling and proof-load tests and were nondestructively evaluated before and after these tests. Correlation of NDE, thermocycling, and proof-load test results made it possible to define requirements for NDT of composite parts and to develop accept/reject criteria. 41700
Mopsik, F.1.; Chang, S.-S.; Hunston, D.L.
Dielectric measurements for cure monitoring Materials Evaluation, Vol. 47, No, 4, pp. 448-453 (Apr. 1989) The use of dielectric measurements to monitor the cure of epoxy resins is investigated. Time-domain spectroscopy and an automated wide- dynamic-range AC-conductance measuring system show that dielectric loss and conductance measurements follow the entire cure cycle with good sensitivity and resolution. Comparisons with viscosity, differential scanning calorimetry (DSC) exotherm, and shear-mode ultrasonic attenuation measurements made simultaneously on the same sample show that dielectric methods compare very favourably with the others. In addition, a limit to the validity of a direct, simple relation between viscosity and dielectric loss is discussed. The conditions necessary for meaningful measurements are considered along with possible implementations of the method. 41653
Johnson, W.S.
Screening of metal matrix composites using ultrasonic C-scans Journal of Composites Technology and Research, Vol. 11, No. 1, pp. 31- 34 (Spring 1989) This paper will show how ultrasonic C-scans can be used to find some types of defects in continuous fiber reinforced metal matrix composites ;such as boron/aluminum composites. These defects will then be related to the fatigue behavior and fracture location of each inspected specimen. The C-scan technique was used to determine the relative amount of defects in boron/aluminum composites. The defects were primarily identified as gaps in the fibre lives, lower fatigue endurance limits, and greater reductions in the elastic unloading modulus (that is, stiffness) because of fatigue cycling. This type of data could be used to set accept-reject levels for a composite panel based on C-scan indications. 41640
Aussel, J. D; Monchalin, J.-P.
Precision laser-ultrasonic velocity measurement and elastic constant determination Ultrasonics, Vol. 27, No. 3, pp. 165-177 (May 1989) A laser-ultrasonic method to measure the acoustic velocities and the elastic constants of solid materials based on the crosscorrelation of successive echoes is presented. Measurements are performed in the thermoclastic regime or slight ablation regime, which permits simultaneous measurement of longitudinal shear velocities and an unlimited number of shots at the specimen. Diffraction corrections re calculated, and dispersion effects are evaluated by frequency analysis. The precision and accuracy of the technique are estimated in terms of sampling rate, thickness of the sample, signal-to-noise ratio, frequency bandwidth and laser-beam alignment. Examples of applications of the technique are given for PZT ceramic, metal-ceramic composites and single crystal germanium.
231
Kenurth, D.C.; Telschow, K.L.; Walter J.B.
Characterization of porosity distributions in advanced ceramics: a comparison of ultrasonic methods Materials Evaluation, Vol. 47, No. 5, pp. 571-575 (May 1989) This paper describes the characterization of an SiC sample that was intentionally processed to contain a distinctly nonuniform porosity distribution. The characterization was done with optical microscopy, radiography, and ultrasonic techniques, which recorded C-scan images of scatterer time of flight, backscatter energy, group velocity, and back- surface echo energy. All of the techniques delineated the porosity distribution in varying degrees and different ways, Significant modulation effects were observed in the back-surface echo-energy measurements because of the nonuniformity in the porosity distribution. This technique proved to be very sensitive to large spatial gradients in the porosity distributions. The velocity measurements were the most accurate in determining the local value of the porosity. These results demonstrate the usefulness of ultrasonic probes for porosity determination in materials with nonuniform spatial distributions. 41806
Cawley, P.; Adams, R.D.
Sensitivity of the coin-tap method of nondestructive testing Materials Evaluation, Vol. 47, No. 5, pp. 558-563 (May 1989) The sensitivity of an automated version of the coin-tap method of nondestructive testing has been investigated. The method has been used to produce C-scan presentations of the defect locations in sets of solid aluminum plates and carbon fiber-reinforced plastic (CFRP) honeycomb panels with deliberately introduced defects. The sensitivity of the method decreases with increasing defect depth, but it has been shown that its sensitivity is somewhat better than that of the mechanical impedance technique. A defect of 10 mm dia under a 1 mm thick CFRP skin is at the margin of detectability, compared with a defect of 20 mm dia using the impedance technique, ft has been shown also that the coin-tap test is more reliable on flexible structures than the mechanical impedance method. No couplant is required between the structure and the tapping head. 41795
Nonaka, T.; Hayakawa, Y.; Takeda, S.; Nishimori, H.
Ultrasonic imaging system for composites and ceramics Materials Evaluation, Vol. 47, No. 5, pp. 542,544-546 (May 1989) Several applications of ultrasonic (US) imaging and data-processing techniques for ceramics and composite materials are described. High frequency US tests can be used to measure very thin delaminations in composites and the very small flaws in ceramics. The system used includes an x-y-z scanner with a transducer, ultrasonic testing units, and a computer for control and data processing. 41784
Wooh, S.C.; Daniel, I.M.
Enhancement techniques for ultrasonic imaging of damage in composite materials New Directions in the Nondestructive Evaluation of Advanced Materials, Winter Annual Meeting, American Society of Mechanical Engineers, Chicago, Illinois, 27 Nov-2 Dec. 1988. Edited by J.L. Rose and A.A. Tseng, pp. 53-62. American Society of Mechanical Engineers (1988) Conventional ultrasonic C-scanning sometimes produces distorted and degraded images due to a variety of reasons, including surface roughness, beam dispersion, extraneous noise and imperfect fidelity of the total acquisition system, Enhancement techniques, using computer data acquisition and processing, can be used to enhance and restore the image. Enhancement techniques described include contrast stretching and median filtering, histogram equalization, thresholding, dynamic thresholding, thresholding depending on boundary characteristics, one- dimensional segmentation and intensity scans with hidden line removal. These enhancement techniques were applied and illustrated for five different types of damage in graphite/epoxy composite materials, embedded film patch in quasi-isotropic laminate, impact damage in quasi-isotropic laminate, matrix cracking due to static loading of crossply laminate, fatigue damage in crossply laminate, and thermally induced cracks in a thick crossply laminate. There is no single technique that is optimum in all cases. A suitable combination of techniques must be selected for optimum image quality. 41782
Kline, R.A.
Quantitative NDE of advanced composites using ultrasonic velocity measurements New Directions in the Nondestructive Evaluation of Advanced Materials, Winter Annual Meeting, American Society of Mechanical Engineers, Chicago, Illinois, 27 Nov-2 Dec. 1988. Edited by J.L. Rose and A . A . Tseng, pp. 35-40. American Society of Mechanical Engineers (1988)
NDT International August 1990
In this work, the use of ultrasonic velocity analysis for the quantitative nondestructive evaluation of the mechanical properties of composite laminates is discussed. The composite laminate is modeled as a layer or set of layers of transversely isotropic material of known orientation. The method described utilizes velocity measurements for ultrasonic wave propagation at multiple angles of incidence. Since the equations are algebraically cumbersome, a numerical procedure employing a commercially available nonlinear equation solving subroutine is utilized. Applications to composite laminates are presented. 41765
Clarke, W.G., Jr.; lyer, J.N.
Structure modeling and the nondestructive evaluation of metal-matrix composites Materials Evaluation, Vol. 47, No. 4, pp. 460-465 (Apr. 1989) Powder metallurgy and liquid mercury modeling techniques were used to replicate the microstructure of metal-matrix composite materials. These models, in turn, were used to establish eddy current and ultrasonic inspection signatures for a variety of structure variables. The impact of matrix chemistry, reinforcement type (shape, sizes, etc.), interface conditions, reinforcement loading, and material processing on nondestructive evaluation (NDE) response was established, These results provide guidelines for the analysis of relevant vs. nonrelevant inspection results as well as a basis for in-process NDE options. The experimental effort was directed specifically at the silicon carbine- reinforced aluminum system but the observations and conclusions are widely applicable to metal-matrix composites in general. 41755
Rogovsky, A.J.
Engineering selection of NDT techniques and accept/reject criteria for composites New Directions in the Nondestructive Evaluation of Advanced Materials, Winter Annual Meeting, American Society of Mechanical Engineers, Chicago, Illinois, 27 Nov-2 Dec. 1988. Edited by J.L. Rose and A.A. Tseng, pp. 45-52. American Society of Mechanical Engineers (1988) Several types of honeycomb and graphite-epoxy composites were investigated to determine appropriate techniques and accept/reject criteria for NDT. Samples with built-in defects of various types, sizes, and locations were designed and fabricated. Ultrasonic, infrared imaging, and x-ray techniques were applied for flaw detection, sizing and characterization. Composite samples with and without defects under-went thermocycling and proof-load tests and were nondestructively evaluated before and after these tests. Correlation of NDE, thermocycling, and proof-load test results made it possible to define requirements for NDT of composite parts and to develop accept/reject criteria. 41700
Mopsik, F.1.; Chang, S.-S.; Hunston, D.L.
Dielectric measurements for cure monitoring Materials Evaluation, Vol. 47, No, 4, pp. 448-453 (Apr. 1989) The use of dielectric measurements to monitor the cure of epoxy resins is investigated. Time-domain spectroscopy and an automated wide- dynamic-range AC-conductance measuring system show that dielectric loss and conductance measurements follow the entire cure cycle with good sensitivity and resolution. Comparisons with viscosity, differential scanning calorimetry (DSC) exotherm, and shear-mode ultrasonic attenuation measurements made simultaneously on the same sample show that dielectric methods compare very favourably with the others. In addition, a limit to the validity of a direct, simple relation between viscosity and dielectric loss is discussed. The conditions necessary for meaningful measurements are considered along with possible implementations of the method. 41653
Johnson, W.S.
Screening of metal matrix composites using ultrasonic C-scans Journal of Composites Technology and Research, Vol. 11, No. 1, pp. 31- 34 (Spring 1989) This paper will show how ultrasonic C-scans can be used to find some types of defects in continuous fiber reinforced metal matrix composites ;such as boron/aluminum composites. These defects will then be related to the fatigue behavior and fracture location of each inspected specimen. The C-scan technique was used to determine the relative amount of defects in boron/aluminum composites. The defects were primarily identified as gaps in the fibre lives, lower fatigue endurance limits, and greater reductions in the elastic unloading modulus (that is, stiffness) because of fatigue cycling. This type of data could be used to set accept-reject levels for a composite panel based on C-scan indications. 41640
Aussel, J. D; Monchalin, J.-P.
Precision laser-ultrasonic velocity measurement and elastic constant determination Ultrasonics, Vol. 27, No. 3, pp. 165-177 (May 1989) A laser-ultrasonic method to measure the acoustic velocities and the elastic constants of solid materials based on the crosscorrelation of successive echoes is presented. Measurements are performed in the thermoclastic regime or slight ablation regime, which permits simultaneous measurement of longitudinal shear velocities and an unlimited number of shots at the specimen. Diffraction corrections re calculated, and dispersion effects are evaluated by frequency analysis. The precision and accuracy of the technique are estimated in terms of sampling rate, thickness of the sample, signal-to-noise ratio, frequency bandwidth and laser-beam alignment. Examples of applications of the technique are given for PZT ceramic, metal-ceramic composites and single crystal germanium.
231