Kanji Ono | University of California, Los Angeles (original) (raw)
Papers by Kanji Ono
This paper reviews progress in methods of signal analysis used in acoustic emission (AE) as appli... more This paper reviews progress in methods of signal analysis used in acoustic emission (AE) as applied to materials research field. The achievement and inadequacy in understanding of AE from materials during the deformation, fracture and other processes are examined systematically. New goals for the future are also discussed in view of new analytical tools and vastly advanced instrumentation.
: It is well known that the ductility of a steel plate, particularly in the thickness (short tran... more : It is well known that the ductility of a steel plate, particularly in the thickness (short transverse) direction, is sensitive to the number, size, shape and distribution of nonmetallic (primarily MnS) inclusions. In this study, acoustic emission behavior was correlated to several inclusion parameters, varied by rolling mill practices and different sulphur levels in the steel used. Burst-type acoustic emission signals were observed in the thickness direction samples. Their numbers and intensity increased with the sulphur content, and also depended on the rolling ratio and finish rolling temperature. The origin of burst emission was established as the decohesion of flattened MnS inclusions. Amplitude distribution of acoustic emission signals was describable by a Weibull distribution. It was also found that the size distribution of MnS inclusions takes an identical form. The two independently determined distributions were correlated by considering the stored elastic strain energy at...
Journal of Composites Science
Ultrasonic attenuation measurements were conducted on cross-ply and quasi-isotropic lay-ups of ei... more Ultrasonic attenuation measurements were conducted on cross-ply and quasi-isotropic lay-ups of eight types of carbon-fiber reinforced composites (CFRPs) using through-transmission methods with diffraction correction. Attenuation values were substantially higher than those of unidirectional composites and other structural materials. Wave modes, fiber distributions, matrix resins, and consolidation methods affected total attenuation. Transverse mode, quasi-isotropic lay-up, and polyimide and thermoplastic resins generally produced higher attenuation. No clear trends from the fiber distribution were revealed, indicating that it is not feasible presently to predict the attenuation of various lay-ups from the unidirectional values. That is, direct attenuation tests for different laminate lay-ups are needed. This work expanded the existing attenuation database by properly determining the attenuation coefficients of two additional layup types of CFRP laminates. Results showed the merit of ...
Techniques of acoustic emission (AE) were used during the over-straining applied on straight pipe... more Techniques of acoustic emission (AE) were used during the over-straining applied on straight pipes and elbows of a polyethylene reactor operating in a factory. This reactor has several dozen pipes, straight and bent, of 10-m length. Over-straining is done before the pipes were put in operation and also periodically during service. AE enables us to monitor the stability of the deformation process and indicates the zones, which will require further detailed examinations by other NDT techniques; it should also improve safety during this process through early detection of critical damage. After a few series of tests and using evaluation criteria with AE parameters, we examined next 45 pipes with recorded waveforms for additional analysis. Vallen VisualClass pattern recognition analysis program enabled us to separate the signals due to the plastic deformation of materials during over-straining process from the signals generated by cracking damage. The presence of damages in three groups of over-strained pipes was identified and confirmed by other NDT techniques.
日本複合材料学会研究発表講演会予稿集, Jun 1, 2001
The Proceedings of the Materials and processing conference, 2003
Dispersion relation Qf hol1Qw cy ！indrical guided waves as a function Qf the ratio of diameter to... more Dispersion relation Qf hol1Qw cy ！indrical guided waves as a function Qf the ratio of diameter to thickness for the measurement of pipe walithickness
Journal of Reinforced Plastics and Composites, 1988
This paper reports an experimental investigation on mechanical and acoustic emission behavior of ... more This paper reports an experimental investigation on mechanical and acoustic emission behavior of specially designed and manufactured carbon fiber epoxy composites. Uni directional composite laminates with various flaw configurations were tested in tension and their mechanical and acoustic emission responses were determined. Fiber fracture, delamination, splitting (or cracking along fibers) and friction of delaminated faces contrib uted to characteristic acoustic emission behavior. These can be discrimination on the basis of peak amplitude and event duration of observed acoustic emission signals. The short duration ( < 100 μs), lower amplitude signals ( < 50 dB) signify carbon fiber fracture, while the medium amplitude signals (50 ∼ 70 dB) with an average event dura tion of —120 μs indicate the initiation and slow growth of delamination. High amplitude events ( > 70 dB) have long ( > 200 μs) event durations and are caused by rapid advances of delamination. Splitting or cr...
J. Acoust. Emiss, 2008
We have obtained the transfer functions of a wide range of AE sensors commonly available and util... more We have obtained the transfer functions of a wide range of AE sensors commonly available and utilized. These were determined by the excitation of input waves using an ultrasonic transmitter or pulse-laser in conjunction with a transfer block, a laser interferometer and a deconvolution procedure typically in the frequency domain. Sensor responses depend on the wave types; i.e., plane waves, and spherical waves with different radius of curvature. Using typical source waveforms and a convolution procedure, one can then visualize waveforms expected out of these AE sensors. Some sensors showed displacement response, while another gave velocity response. These response types also depended on incident wave types, requiring additional characterization steps in sensor calibration procedures.
The paper presents the Lamb wave attenuation of Carbon Fiber Reinforced Plastic (CFRP) plates on ... more The paper presents the Lamb wave attenuation of Carbon Fiber Reinforced Plastic (CFRP) plates on the basis of an experimental transmitter-sensor scheme. We measured separately the S 0 and A 0 Lamb modes of CFRP plates with three different kind of laminate lay-ups; unidirectional [0] 8s (and [90] 8s), cross-ply [0, 90] 4s , and quasi-isotropic [0,45,-45,90] 2s. Several ultrasound transmitters were used as actuator and short-duration high-voltage pulses were used for excitation. Two kinds of AE resonant sensors with resonance frequency around 260 and 500 kHz, respectively, were used to record the Lamb waveforms of the plates. By using sensors on both sides of the plate, the confirmation and separation of both modes, S 0 and A 0 , were successfully carried out. This result was also confirmed by using the wavelet transform of the recorded signals. The experiment was carried out at several transmitter-sensor distances, so both phase and group velocities and attenuation could be obtained. By means an appropriate fitting of a theoretical model of attenuation, including the geometrical attenuation, the damping factor of both modes was obtained for each laminate and sensing frequency. The experimental results for velocities and damping factors were compared with previously published and theoretical ones. Directivity results are also reported, showing complex behavior dependent on laminate layups as expected.
Elsevier eBooks, 2000
Abstract Using Lamb wave analysis, the impact dynamcis and resultant fracture of a circular 3-mm-... more Abstract Using Lamb wave analysis, the impact dynamcis and resultant fracture of a circular 3-mm-thick polymethylmethacrylate (PMMA) plate subjected to transverse ball impact at up to 23 m/s were studied. The time history of the impact force was estimated by deconvolution analysis and waveform synthesis of the Lamb waves. The estimated force history for low velocity was consistent with the output of a piezoelectric film, which measured the force duration directly. The dynamics of local fracture in a plate hit by a ball impact were analyzed by waveform simulation of the fracture-induced acoustic emission. A 22-mm-long crack generated by a 21-m/s impact on a plate with a slit was modeled.
Sensors
Ultrasonic non-destructive evaluation, which has been used widely, can detect and size critical f... more Ultrasonic non-destructive evaluation, which has been used widely, can detect and size critical flaws in structures. Advances in sound field calculations can further improve its effectiveness. Two calculation methods were used to characterize the relevant sound fields of an ultrasonic transducer and the results were applied to construct and evaluate Distance-Gain-Size (DGS) diagrams, which are useful in flaw sizing. Two published DGS diagrams were found to be deficient because the backward diffraction path was overly simplified and the third one included an arbitrary procedure. Newly constructed DGS diagrams exhibited transducer size dependence, revealing another deficiency in the existing DGS diagrams. However, the extent of the present calculations must be expanded to provide a catalog of DGS diagrams to cover a wide range of practical needs. Details of the new construction method are presented, incorporating two-way diffraction procedures.
Transportation Research Record: Journal of the Transportation Research Board, 2012
After the discovery of a significant crack in an eyebar (fracture-critical element) on the San Fr... more After the discovery of a significant crack in an eyebar (fracture-critical element) on the San Francisco–Oakland Bay Bridge in California, the California Department of Transportation (Caltrans) explored possible remote monitor solutions to provide the greatest possible safeguards for the some 200,000 vehicles that used the bridge daily. Caltrans selected an acoustic emission (AE) monitoring system that allowed the detection and localization of crack initiation and growth in real time. The AE method relies on the propagation of elastic waves released by a sudden stress–strain change at the crack tip. The challenge of the AE method in a field application is the disturbance of the data by extraneous noise sources. A robust damage detection algorithm is required to differentiate relevant damage data from secondary noise sources, such as friction. Caltrans required that the proposed monitoring solution be validated through laboratory testing. This paper presents the full-scale laboratory...
Transportation Research Record: Journal of the Transportation Research Board, , 2012
The impulse response of the velocity potential and the discrete representation methods were used ... more The impulse response of the velocity potential and the discrete representation methods were used in order to model the acoustic field radiated by ultrasonic transducers and arrays. The first method deals with the calculation of the exact impulse response, in which solutions are possible only for simple geometries, such as the circular piston. The second method is an approximated solution based on the discretization of the acoustic aperture in small elementary areas, each of them radiating a spherical wave. By using circular transducers, which can be considered circular pistons, many simulations comparing the methods were carried out. The relation between the computational cost and the precision was analyzed, thus establishing the time and space discretization levels. The simulations were made using the Matlab software and the results were compared to experimental measurements showing good agreement. The experimental results were obtained using a scanning system. The acoustic field radiated from a 1 MHz circular transducer was measured as well as a 3.5 MHz array of 16 elements both immersed in water. The acoustic field radiated by the array was simulated and measured with focalization on a radius of 30 mm with deflections of 0° and 20°.
Applied Sciences
Ultrasonic attenuation coefficients of ceramic and inorganic materials were determined for the lo... more Ultrasonic attenuation coefficients of ceramic and inorganic materials were determined for the longitudinal and transverse wave modes. Sample materials included hard and soft ceramics, common ceramics, ceramic-matrix composites, mortars, silicate glasses, rocks, minerals and crystals. For ceramic attenuation measurements, a standardized method has existed, but this method based on a buffer-rod arrangement was found to be inconsistent, producing vastly different results. Resonant ultrasound spectroscopy was also found to be unworkable from its sample preparation requirements. Experimental reevaluation of the buffer-rod method showed its impracticality due to unpredictable reflectivity parameters, yielding mostly negative attenuation coefficients. In this work, attenuation tests relied on a through-transmission method, which incorporated a correction procedure for diffraction losses. Attenuation exhibited four types of frequency (f) dependence, i.e., linear, linear plus f4 (called Mas...
Appl Sci, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Applied Sciences
This work determined the attenuation coefficients of Lamb waves of ten engineering materials and ... more This work determined the attenuation coefficients of Lamb waves of ten engineering materials and compared the results with calculated Lamb-wave attenuation coefficients, α–S and α–A. The Disperse program and a parametric method based on Disperse results were used for calculations. Bulk-wave attenuation coefficients, αL and αT, were required as input parameters to the Disperse calculations. The calculated α–S and α–A values were found to be dominated by the αT contribution. Often α–Ao coincided with αT. The values of αL and αT were previously obtained or newly measured. Attenuation measurement relied on Lamb-wave generation by pulsed excitation of ultrasonic transducers and on surface-displacement detection with point contact receivers. The frequency used ranged from 10 kHz to 1 MHz. A total of 14 sheet and plate samples were evaluated. Sample materials ranged from steel, Al, and silicate glass with low attenuation to polymers and a fiber composite with much higher attenuation. Exper...
International Journal of Fracture, 1982
The authors wish to dedicate this paper in memory of the late Professor Alan S. Tetelman.) ABSTRA... more The authors wish to dedicate this paper in memory of the late Professor Alan S. Tetelman.) ABSTRACT A new model that is capable of predicting and explaining the effect of cyclic loading on the apparent fracture toughness of materials was developed. The model combines macroscopic fracture criteria with the assumption that transient flow properties of material in the cyclic plastic zone can be simulated by those of macroscopic low cycle fatigue specimens, tested in reversed strain control. Little or no changes in the cleavage fracture toughness due to cyclic loading is predicted or observed for materials that cycle strain harden (e.g., rail steel) and in the fracture toughness of other materials that cycle strain harden (e.g., the commercial 2000 series A1-Cu alloys) and fracture by rupture. However, an increase in the fracture toughness is predicted and observed for materials that cycle strain soften (e.g., ICr-Mo-V and 18 Ni 300 maraging steels), irrespective of fracture mode (cleavage or rupture). The changes in the fracture toughness are predicted and observed to increase with both the number of cycles of applied load and the reversed plastic strain range (or stress intensity range for precracked specimens).
AIP Conference Proceedings, 1999
ABSTRACT The present work has evaluated the elastic properties of low-pressure plasma-sprayed NiC... more ABSTRACT The present work has evaluated the elastic properties of low-pressure plasma-sprayed NiCrAlY and atmospheric plasma-sprayed ZrO2-8%Y2O3 materials at ambient and elevated temperatures up to 900 °C by using a laser surface acoustic wave (SAW) technique. Lamb (Rayleigh) waves were excited in free-standing films (sprayed coatings) by a pulsed-YAG-laser irradiation. The dispersive group velocities of A0-mode Lamb waves were utilized in evaluating the elastic properties of the films. The results indicated that the Young's moduli (E) and densities (rho) of the sprayed materials, especially sprayed ZrO2, were lower than those of dense materials and decreased with increasing temperature. Deviation in the Rayleigh wave dispersion curves suggests a means of determining the integrity of interfaces.
This paper reviews progress in methods of signal analysis used in acoustic emission (AE) as appli... more This paper reviews progress in methods of signal analysis used in acoustic emission (AE) as applied to materials research field. The achievement and inadequacy in understanding of AE from materials during the deformation, fracture and other processes are examined systematically. New goals for the future are also discussed in view of new analytical tools and vastly advanced instrumentation.
: It is well known that the ductility of a steel plate, particularly in the thickness (short tran... more : It is well known that the ductility of a steel plate, particularly in the thickness (short transverse) direction, is sensitive to the number, size, shape and distribution of nonmetallic (primarily MnS) inclusions. In this study, acoustic emission behavior was correlated to several inclusion parameters, varied by rolling mill practices and different sulphur levels in the steel used. Burst-type acoustic emission signals were observed in the thickness direction samples. Their numbers and intensity increased with the sulphur content, and also depended on the rolling ratio and finish rolling temperature. The origin of burst emission was established as the decohesion of flattened MnS inclusions. Amplitude distribution of acoustic emission signals was describable by a Weibull distribution. It was also found that the size distribution of MnS inclusions takes an identical form. The two independently determined distributions were correlated by considering the stored elastic strain energy at...
Journal of Composites Science
Ultrasonic attenuation measurements were conducted on cross-ply and quasi-isotropic lay-ups of ei... more Ultrasonic attenuation measurements were conducted on cross-ply and quasi-isotropic lay-ups of eight types of carbon-fiber reinforced composites (CFRPs) using through-transmission methods with diffraction correction. Attenuation values were substantially higher than those of unidirectional composites and other structural materials. Wave modes, fiber distributions, matrix resins, and consolidation methods affected total attenuation. Transverse mode, quasi-isotropic lay-up, and polyimide and thermoplastic resins generally produced higher attenuation. No clear trends from the fiber distribution were revealed, indicating that it is not feasible presently to predict the attenuation of various lay-ups from the unidirectional values. That is, direct attenuation tests for different laminate lay-ups are needed. This work expanded the existing attenuation database by properly determining the attenuation coefficients of two additional layup types of CFRP laminates. Results showed the merit of ...
Techniques of acoustic emission (AE) were used during the over-straining applied on straight pipe... more Techniques of acoustic emission (AE) were used during the over-straining applied on straight pipes and elbows of a polyethylene reactor operating in a factory. This reactor has several dozen pipes, straight and bent, of 10-m length. Over-straining is done before the pipes were put in operation and also periodically during service. AE enables us to monitor the stability of the deformation process and indicates the zones, which will require further detailed examinations by other NDT techniques; it should also improve safety during this process through early detection of critical damage. After a few series of tests and using evaluation criteria with AE parameters, we examined next 45 pipes with recorded waveforms for additional analysis. Vallen VisualClass pattern recognition analysis program enabled us to separate the signals due to the plastic deformation of materials during over-straining process from the signals generated by cracking damage. The presence of damages in three groups of over-strained pipes was identified and confirmed by other NDT techniques.
日本複合材料学会研究発表講演会予稿集, Jun 1, 2001
The Proceedings of the Materials and processing conference, 2003
Dispersion relation Qf hol1Qw cy ！indrical guided waves as a function Qf the ratio of diameter to... more Dispersion relation Qf hol1Qw cy ！indrical guided waves as a function Qf the ratio of diameter to thickness for the measurement of pipe walithickness
Journal of Reinforced Plastics and Composites, 1988
This paper reports an experimental investigation on mechanical and acoustic emission behavior of ... more This paper reports an experimental investigation on mechanical and acoustic emission behavior of specially designed and manufactured carbon fiber epoxy composites. Uni directional composite laminates with various flaw configurations were tested in tension and their mechanical and acoustic emission responses were determined. Fiber fracture, delamination, splitting (or cracking along fibers) and friction of delaminated faces contrib uted to characteristic acoustic emission behavior. These can be discrimination on the basis of peak amplitude and event duration of observed acoustic emission signals. The short duration ( < 100 μs), lower amplitude signals ( < 50 dB) signify carbon fiber fracture, while the medium amplitude signals (50 ∼ 70 dB) with an average event dura tion of —120 μs indicate the initiation and slow growth of delamination. High amplitude events ( > 70 dB) have long ( > 200 μs) event durations and are caused by rapid advances of delamination. Splitting or cr...
J. Acoust. Emiss, 2008
We have obtained the transfer functions of a wide range of AE sensors commonly available and util... more We have obtained the transfer functions of a wide range of AE sensors commonly available and utilized. These were determined by the excitation of input waves using an ultrasonic transmitter or pulse-laser in conjunction with a transfer block, a laser interferometer and a deconvolution procedure typically in the frequency domain. Sensor responses depend on the wave types; i.e., plane waves, and spherical waves with different radius of curvature. Using typical source waveforms and a convolution procedure, one can then visualize waveforms expected out of these AE sensors. Some sensors showed displacement response, while another gave velocity response. These response types also depended on incident wave types, requiring additional characterization steps in sensor calibration procedures.
The paper presents the Lamb wave attenuation of Carbon Fiber Reinforced Plastic (CFRP) plates on ... more The paper presents the Lamb wave attenuation of Carbon Fiber Reinforced Plastic (CFRP) plates on the basis of an experimental transmitter-sensor scheme. We measured separately the S 0 and A 0 Lamb modes of CFRP plates with three different kind of laminate lay-ups; unidirectional [0] 8s (and [90] 8s), cross-ply [0, 90] 4s , and quasi-isotropic [0,45,-45,90] 2s. Several ultrasound transmitters were used as actuator and short-duration high-voltage pulses were used for excitation. Two kinds of AE resonant sensors with resonance frequency around 260 and 500 kHz, respectively, were used to record the Lamb waveforms of the plates. By using sensors on both sides of the plate, the confirmation and separation of both modes, S 0 and A 0 , were successfully carried out. This result was also confirmed by using the wavelet transform of the recorded signals. The experiment was carried out at several transmitter-sensor distances, so both phase and group velocities and attenuation could be obtained. By means an appropriate fitting of a theoretical model of attenuation, including the geometrical attenuation, the damping factor of both modes was obtained for each laminate and sensing frequency. The experimental results for velocities and damping factors were compared with previously published and theoretical ones. Directivity results are also reported, showing complex behavior dependent on laminate layups as expected.
Elsevier eBooks, 2000
Abstract Using Lamb wave analysis, the impact dynamcis and resultant fracture of a circular 3-mm-... more Abstract Using Lamb wave analysis, the impact dynamcis and resultant fracture of a circular 3-mm-thick polymethylmethacrylate (PMMA) plate subjected to transverse ball impact at up to 23 m/s were studied. The time history of the impact force was estimated by deconvolution analysis and waveform synthesis of the Lamb waves. The estimated force history for low velocity was consistent with the output of a piezoelectric film, which measured the force duration directly. The dynamics of local fracture in a plate hit by a ball impact were analyzed by waveform simulation of the fracture-induced acoustic emission. A 22-mm-long crack generated by a 21-m/s impact on a plate with a slit was modeled.
Sensors
Ultrasonic non-destructive evaluation, which has been used widely, can detect and size critical f... more Ultrasonic non-destructive evaluation, which has been used widely, can detect and size critical flaws in structures. Advances in sound field calculations can further improve its effectiveness. Two calculation methods were used to characterize the relevant sound fields of an ultrasonic transducer and the results were applied to construct and evaluate Distance-Gain-Size (DGS) diagrams, which are useful in flaw sizing. Two published DGS diagrams were found to be deficient because the backward diffraction path was overly simplified and the third one included an arbitrary procedure. Newly constructed DGS diagrams exhibited transducer size dependence, revealing another deficiency in the existing DGS diagrams. However, the extent of the present calculations must be expanded to provide a catalog of DGS diagrams to cover a wide range of practical needs. Details of the new construction method are presented, incorporating two-way diffraction procedures.
Transportation Research Record: Journal of the Transportation Research Board, 2012
After the discovery of a significant crack in an eyebar (fracture-critical element) on the San Fr... more After the discovery of a significant crack in an eyebar (fracture-critical element) on the San Francisco–Oakland Bay Bridge in California, the California Department of Transportation (Caltrans) explored possible remote monitor solutions to provide the greatest possible safeguards for the some 200,000 vehicles that used the bridge daily. Caltrans selected an acoustic emission (AE) monitoring system that allowed the detection and localization of crack initiation and growth in real time. The AE method relies on the propagation of elastic waves released by a sudden stress–strain change at the crack tip. The challenge of the AE method in a field application is the disturbance of the data by extraneous noise sources. A robust damage detection algorithm is required to differentiate relevant damage data from secondary noise sources, such as friction. Caltrans required that the proposed monitoring solution be validated through laboratory testing. This paper presents the full-scale laboratory...
Transportation Research Record: Journal of the Transportation Research Board, , 2012
The impulse response of the velocity potential and the discrete representation methods were used ... more The impulse response of the velocity potential and the discrete representation methods were used in order to model the acoustic field radiated by ultrasonic transducers and arrays. The first method deals with the calculation of the exact impulse response, in which solutions are possible only for simple geometries, such as the circular piston. The second method is an approximated solution based on the discretization of the acoustic aperture in small elementary areas, each of them radiating a spherical wave. By using circular transducers, which can be considered circular pistons, many simulations comparing the methods were carried out. The relation between the computational cost and the precision was analyzed, thus establishing the time and space discretization levels. The simulations were made using the Matlab software and the results were compared to experimental measurements showing good agreement. The experimental results were obtained using a scanning system. The acoustic field radiated from a 1 MHz circular transducer was measured as well as a 3.5 MHz array of 16 elements both immersed in water. The acoustic field radiated by the array was simulated and measured with focalization on a radius of 30 mm with deflections of 0° and 20°.
Applied Sciences
Ultrasonic attenuation coefficients of ceramic and inorganic materials were determined for the lo... more Ultrasonic attenuation coefficients of ceramic and inorganic materials were determined for the longitudinal and transverse wave modes. Sample materials included hard and soft ceramics, common ceramics, ceramic-matrix composites, mortars, silicate glasses, rocks, minerals and crystals. For ceramic attenuation measurements, a standardized method has existed, but this method based on a buffer-rod arrangement was found to be inconsistent, producing vastly different results. Resonant ultrasound spectroscopy was also found to be unworkable from its sample preparation requirements. Experimental reevaluation of the buffer-rod method showed its impracticality due to unpredictable reflectivity parameters, yielding mostly negative attenuation coefficients. In this work, attenuation tests relied on a through-transmission method, which incorporated a correction procedure for diffraction losses. Attenuation exhibited four types of frequency (f) dependence, i.e., linear, linear plus f4 (called Mas...
Appl Sci, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Applied Sciences
This work determined the attenuation coefficients of Lamb waves of ten engineering materials and ... more This work determined the attenuation coefficients of Lamb waves of ten engineering materials and compared the results with calculated Lamb-wave attenuation coefficients, α–S and α–A. The Disperse program and a parametric method based on Disperse results were used for calculations. Bulk-wave attenuation coefficients, αL and αT, were required as input parameters to the Disperse calculations. The calculated α–S and α–A values were found to be dominated by the αT contribution. Often α–Ao coincided with αT. The values of αL and αT were previously obtained or newly measured. Attenuation measurement relied on Lamb-wave generation by pulsed excitation of ultrasonic transducers and on surface-displacement detection with point contact receivers. The frequency used ranged from 10 kHz to 1 MHz. A total of 14 sheet and plate samples were evaluated. Sample materials ranged from steel, Al, and silicate glass with low attenuation to polymers and a fiber composite with much higher attenuation. Exper...
International Journal of Fracture, 1982
The authors wish to dedicate this paper in memory of the late Professor Alan S. Tetelman.) ABSTRA... more The authors wish to dedicate this paper in memory of the late Professor Alan S. Tetelman.) ABSTRACT A new model that is capable of predicting and explaining the effect of cyclic loading on the apparent fracture toughness of materials was developed. The model combines macroscopic fracture criteria with the assumption that transient flow properties of material in the cyclic plastic zone can be simulated by those of macroscopic low cycle fatigue specimens, tested in reversed strain control. Little or no changes in the cleavage fracture toughness due to cyclic loading is predicted or observed for materials that cycle strain harden (e.g., rail steel) and in the fracture toughness of other materials that cycle strain harden (e.g., the commercial 2000 series A1-Cu alloys) and fracture by rupture. However, an increase in the fracture toughness is predicted and observed for materials that cycle strain soften (e.g., ICr-Mo-V and 18 Ni 300 maraging steels), irrespective of fracture mode (cleavage or rupture). The changes in the fracture toughness are predicted and observed to increase with both the number of cycles of applied load and the reversed plastic strain range (or stress intensity range for precracked specimens).
AIP Conference Proceedings, 1999
ABSTRACT The present work has evaluated the elastic properties of low-pressure plasma-sprayed NiC... more ABSTRACT The present work has evaluated the elastic properties of low-pressure plasma-sprayed NiCrAlY and atmospheric plasma-sprayed ZrO2-8%Y2O3 materials at ambient and elevated temperatures up to 900 °C by using a laser surface acoustic wave (SAW) technique. Lamb (Rayleigh) waves were excited in free-standing films (sprayed coatings) by a pulsed-YAG-laser irradiation. The dispersive group velocities of A0-mode Lamb waves were utilized in evaluating the elastic properties of the films. The results indicated that the Young's moduli (E) and densities (rho) of the sprayed materials, especially sprayed ZrO2, were lower than those of dense materials and decreased with increasing temperature. Deviation in the Rayleigh wave dispersion curves suggests a means of determining the integrity of interfaces.