The Experts below are selected from a list of 6327 Experts worldwide ranked by ideXlab platform
Fuhgwo Yuan - One of the best experts on this subject based on the ideXlab platform.
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barely visible impact damage imaging using non contact air Coupled Transducer laser doppler vibrometer system
Structural Health Monitoring-an International Journal, 2017Co-Authors: Fuhgwo YuanAbstract:The aim of this study is to investigate the capability of the zero-lag cross-correlation imaging condition of an A0 Lamb wave mode in imaging a barely visible impact damage in a carbon fiber–reinforced polymer composite using a fully non-contact-guided wave-based non-destructive inspection system. A 16-ply (45/0/-45/90)2s carbon fiber–reinforced polymer laminate was impacted at three different locations with different impact energies using a drop ball at three drop heights causing three barely visible impact damages with different sizes. The A0 Lamb wave mode is generated inside the laminate using a circular air-Coupled Transducer and detected along the damaged region using a laser Doppler vibrometer. The measured wavefield is then decomposed into a forward and backward propagating wavefields by applying a frequency–wavenumber filtering post-processing technique. The decomposed wavefields are then cross-correlated in the frequency domain using zero-lag cross-correlation imaging condition producing a detai...
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imaging of local porosity voids using a fully non contact air Coupled Transducer and laser doppler vibrometer system
Structural Health Monitoring-an International Journal, 2017Co-Authors: Fuhgwo Yuan, Tyler B Hudson, Brian W GrimsleyAbstract:This study exploits the feasibility of imaging zones of local porosity/voids simulated by introducing microspheres during layup of a unidirectional carbon fiber–reinforced polymer composite panel. A fully non-contact hybrid system primarily composed of an air-Coupled Transducer and a laser Doppler vibrometer was used for imaging the local porosity/void zones from the guided wave response. To improve image resolution, several preprocessing techniques are performed. The wavefield reconstructed from the laser Doppler vibrometer measurements was first “denoised” using a one-dimensional wavelet transform in the time domain followed by a two-dimensional wavelet transform in the spatial domain. From the total wavefield, the much weaker backscattered waves were separated from the stronger incident wave by frequency–wavenumber domain filtering. In order to further enhance the signal-to-noise ratio and sharpen the image, the attenuation of incident wave propagation to the damage site was compensated through two pro...
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damage imaging using non contact air Coupled Transducer laser doppler vibrometer system
Structural Health Monitoring-an International Journal, 2016Co-Authors: Fuhgwo Yuan, Mohammad HarbAbstract:In this work, a rapid imaging technique is proposed for imaging damage in metallic plates using a zero-lag cross-correlation imaging condition in the frequency domain. A fully non-contact, single-s...
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non contact ultrasonic technique for lamb wave characterization in composite plates
Ultrasonics, 2016Co-Authors: Fuhgwo Yuan, Mohammad HarbAbstract:A fully non-contact single-sided air-Coupled and laser ultrasonic non-destructive system based on the generation and detection of Lamb waves is implemented for the characterization of A0 Lamb wave mode dispersion in a composite plate. An air-Coupled Transducer (ACT) radiates acoustic pressure on the surface of the composite and generates Lamb waves within the structure. The out-of-plane velocity of the propagating wave is measured using a laser Doppler vibrometer (LDV). In this study, the non-contact automated system focuses on measuring A0 mode frequency-wavenumber, phase velocity dispersion curves using Snell's law and group velocity dispersion curves using Morlet wavelet transform (MWT) based on time-of-flight along different wave propagation directions. It is theoretically demonstrated that Snell's law represents a direct link between the phase velocity of the generated Lamb wave mode and the coincidence angle of the ACT. Using Snell's law and MWT, the former three dispersion curves of the A0 mode are easily and promptly generated from a set of measurements obtained from a rapid ACT angle scan experiment. In addition, the phase velocity and group velocity polar characteristic wave curves are also computed to analyze experimentally the angular dependency of Lamb wave propagation. In comparison with the results from the theory, it is confirmed that using the ACT/LDV system and implementing simple Snell's law method is highly sensitive and effective in characterizing the dispersion curves of Lamb waves in composite structures as well as its angular dependency.
Laurence J. Jacobs - One of the best experts on this subject based on the ideXlab platform.
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determination of absolute material nonlinearity with air Coupled ultrasonic receivers
Ultrasonics, 2017Co-Authors: David Torello, Nicholas Selby, Jianmin Qu, Laurence J. JacobsAbstract:Abstract Quantitative evaluation of the microstructural state of a specimen can be deduced from knowledge of the sample’s absolute acoustic nonlinearity parameter, β , making the measurement of β a powerful tool in the NDE toolbox. However, the various methods used in the past to measure β each suffer from significant limitations. Piezoelectric contact Transducers are sensitive to nonlinear signals, cheap, and simple to use, but they are hindered by the variability of the interfacial contact between Transducer and specimen surface. Laser interferometry provides non-contact detection, but requires carefully prepared specimens or complicated optics to maximize sensitivity to the higher harmonic components of a received waveform. Additionally, laser interferometry is expensive and relatively difficult to use in the field. Air-Coupled piezoelectric Transducers offer the strengths of both of these technologies and the weaknesses of neither, but are notoriously difficult to calibrate for use in nonlinear measurements. This work proposes a hybrid modeling and experimental approach to air-Coupled Transducer calibration and the use of this calibration in a model-based optimization to determine the absolute β parameter of the material under investigation. This approach is applied to aluminum and fused silica, which are both well-documented materials and provide a strong reference for comparison of experimental and modeling results.
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determination of absolute material nonlinearity with air Coupled ultrasonic receivers
Ultrasonics, 2017Co-Authors: David Torello, Nicholas Selby, Jianmin Qu, Laurence J. JacobsAbstract:Abstract Quantitative evaluation of the microstructural state of a specimen can be deduced from knowledge of the sample’s absolute acoustic nonlinearity parameter, β , making the measurement of β a powerful tool in the NDE toolbox. However, the various methods used in the past to measure β each suffer from significant limitations. Piezoelectric contact Transducers are sensitive to nonlinear signals, cheap, and simple to use, but they are hindered by the variability of the interfacial contact between Transducer and specimen surface. Laser interferometry provides non-contact detection, but requires carefully prepared specimens or complicated optics to maximize sensitivity to the higher harmonic components of a received waveform. Additionally, laser interferometry is expensive and relatively difficult to use in the field. Air-Coupled piezoelectric Transducers offer the strengths of both of these technologies and the weaknesses of neither, but are notoriously difficult to calibrate for use in nonlinear measurements. This work proposes a hybrid modeling and experimental approach to air-Coupled Transducer calibration and the use of this calibration in a model-based optimization to determine the absolute β parameter of the material under investigation. This approach is applied to aluminum and fused silica, which are both well-documented materials and provide a strong reference for comparison of experimental and modeling results.
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using nonlinear ultrasound to track microstructural changes due to thermal aging in modified 9 cr ferritic martensitic steel
Ndt & E International, 2016Co-Authors: Daniel Marino, Jianmin Qu, Alberto Ruiz, Laurence J. JacobsAbstract:Abstract This research investigates second harmonic generation in Rayleigh surface waves propagating in 9%Cr ferritic martensitic steel. Previous experimental results show that nonlinear ultrasound is sensitive to certain microstructural changes in materials such as those due to thermal embrittlement and precipitation hardening. This research measures the ultrasonic nonlinearity parameter as an indicator of microstructural changes due to thermal aging in 9%Cr ferritic martensitic steel specimens. The specimens are isothermally aged for different holding periods to induce progressive changes in the microstructure and to obtain different levels of thermal damage. As thermal aging progresses, the existing dislocations are annihilated in the beginning and precipitates are formed; these microstructural evolutions lead to large changes in the measured nonlinearity parameter, β. Nonlinear ultrasonic experiments are conducted for each specimen using a wedge Transducer for generation and an air-Coupled Transducer for detection of Rayleigh surface waves. The amplitudes of the first and second order harmonics are measured as a function of propagation distance, and these amplitudes are used to obtain the relative nonlinearity parameter at different aging stages. A possible scenario for the microstructural evolution during thermal aging is proposed based on the results from the nonlinear ultrasonic measurements, scanning electron microscopy (SEM), and Rockwell HRC hardness. These results indicate a clear trend that the measured nonlinearity parameter is sensitive to variations in dislocation and precipitate density, and thus can be useful in tracking microstructural changes in this material during thermal aging.
Mohammad Harb - One of the best experts on this subject based on the ideXlab platform.
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damage imaging using non contact air Coupled Transducer laser doppler vibrometer system
Structural Health Monitoring-an International Journal, 2016Co-Authors: Fuhgwo Yuan, Mohammad HarbAbstract:In this work, a rapid imaging technique is proposed for imaging damage in metallic plates using a zero-lag cross-correlation imaging condition in the frequency domain. A fully non-contact, single-s...
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non contact ultrasonic technique for lamb wave characterization in composite plates
Ultrasonics, 2016Co-Authors: Fuhgwo Yuan, Mohammad HarbAbstract:A fully non-contact single-sided air-Coupled and laser ultrasonic non-destructive system based on the generation and detection of Lamb waves is implemented for the characterization of A0 Lamb wave mode dispersion in a composite plate. An air-Coupled Transducer (ACT) radiates acoustic pressure on the surface of the composite and generates Lamb waves within the structure. The out-of-plane velocity of the propagating wave is measured using a laser Doppler vibrometer (LDV). In this study, the non-contact automated system focuses on measuring A0 mode frequency-wavenumber, phase velocity dispersion curves using Snell's law and group velocity dispersion curves using Morlet wavelet transform (MWT) based on time-of-flight along different wave propagation directions. It is theoretically demonstrated that Snell's law represents a direct link between the phase velocity of the generated Lamb wave mode and the coincidence angle of the ACT. Using Snell's law and MWT, the former three dispersion curves of the A0 mode are easily and promptly generated from a set of measurements obtained from a rapid ACT angle scan experiment. In addition, the phase velocity and group velocity polar characteristic wave curves are also computed to analyze experimentally the angular dependency of Lamb wave propagation. In comparison with the results from the theory, it is confirmed that using the ACT/LDV system and implementing simple Snell's law method is highly sensitive and effective in characterizing the dispersion curves of Lamb waves in composite structures as well as its angular dependency.
David Torello - One of the best experts on this subject based on the ideXlab platform.
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determination of absolute material nonlinearity with air Coupled ultrasonic receivers
Ultrasonics, 2017Co-Authors: David Torello, Nicholas Selby, Jianmin Qu, Laurence J. JacobsAbstract:Abstract Quantitative evaluation of the microstructural state of a specimen can be deduced from knowledge of the sample’s absolute acoustic nonlinearity parameter, β , making the measurement of β a powerful tool in the NDE toolbox. However, the various methods used in the past to measure β each suffer from significant limitations. Piezoelectric contact Transducers are sensitive to nonlinear signals, cheap, and simple to use, but they are hindered by the variability of the interfacial contact between Transducer and specimen surface. Laser interferometry provides non-contact detection, but requires carefully prepared specimens or complicated optics to maximize sensitivity to the higher harmonic components of a received waveform. Additionally, laser interferometry is expensive and relatively difficult to use in the field. Air-Coupled piezoelectric Transducers offer the strengths of both of these technologies and the weaknesses of neither, but are notoriously difficult to calibrate for use in nonlinear measurements. This work proposes a hybrid modeling and experimental approach to air-Coupled Transducer calibration and the use of this calibration in a model-based optimization to determine the absolute β parameter of the material under investigation. This approach is applied to aluminum and fused silica, which are both well-documented materials and provide a strong reference for comparison of experimental and modeling results.
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determination of absolute material nonlinearity with air Coupled ultrasonic receivers
Ultrasonics, 2017Co-Authors: David Torello, Nicholas Selby, Jianmin Qu, Laurence J. JacobsAbstract:Abstract Quantitative evaluation of the microstructural state of a specimen can be deduced from knowledge of the sample’s absolute acoustic nonlinearity parameter, β , making the measurement of β a powerful tool in the NDE toolbox. However, the various methods used in the past to measure β each suffer from significant limitations. Piezoelectric contact Transducers are sensitive to nonlinear signals, cheap, and simple to use, but they are hindered by the variability of the interfacial contact between Transducer and specimen surface. Laser interferometry provides non-contact detection, but requires carefully prepared specimens or complicated optics to maximize sensitivity to the higher harmonic components of a received waveform. Additionally, laser interferometry is expensive and relatively difficult to use in the field. Air-Coupled piezoelectric Transducers offer the strengths of both of these technologies and the weaknesses of neither, but are notoriously difficult to calibrate for use in nonlinear measurements. This work proposes a hybrid modeling and experimental approach to air-Coupled Transducer calibration and the use of this calibration in a model-based optimization to determine the absolute β parameter of the material under investigation. This approach is applied to aluminum and fused silica, which are both well-documented materials and provide a strong reference for comparison of experimental and modeling results.
Jianmin Qu - One of the best experts on this subject based on the ideXlab platform.
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determination of absolute material nonlinearity with air Coupled ultrasonic receivers
Ultrasonics, 2017Co-Authors: David Torello, Nicholas Selby, Jianmin Qu, Laurence J. JacobsAbstract:Abstract Quantitative evaluation of the microstructural state of a specimen can be deduced from knowledge of the sample’s absolute acoustic nonlinearity parameter, β , making the measurement of β a powerful tool in the NDE toolbox. However, the various methods used in the past to measure β each suffer from significant limitations. Piezoelectric contact Transducers are sensitive to nonlinear signals, cheap, and simple to use, but they are hindered by the variability of the interfacial contact between Transducer and specimen surface. Laser interferometry provides non-contact detection, but requires carefully prepared specimens or complicated optics to maximize sensitivity to the higher harmonic components of a received waveform. Additionally, laser interferometry is expensive and relatively difficult to use in the field. Air-Coupled piezoelectric Transducers offer the strengths of both of these technologies and the weaknesses of neither, but are notoriously difficult to calibrate for use in nonlinear measurements. This work proposes a hybrid modeling and experimental approach to air-Coupled Transducer calibration and the use of this calibration in a model-based optimization to determine the absolute β parameter of the material under investigation. This approach is applied to aluminum and fused silica, which are both well-documented materials and provide a strong reference for comparison of experimental and modeling results.
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determination of absolute material nonlinearity with air Coupled ultrasonic receivers
Ultrasonics, 2017Co-Authors: David Torello, Nicholas Selby, Jianmin Qu, Laurence J. JacobsAbstract:Abstract Quantitative evaluation of the microstructural state of a specimen can be deduced from knowledge of the sample’s absolute acoustic nonlinearity parameter, β , making the measurement of β a powerful tool in the NDE toolbox. However, the various methods used in the past to measure β each suffer from significant limitations. Piezoelectric contact Transducers are sensitive to nonlinear signals, cheap, and simple to use, but they are hindered by the variability of the interfacial contact between Transducer and specimen surface. Laser interferometry provides non-contact detection, but requires carefully prepared specimens or complicated optics to maximize sensitivity to the higher harmonic components of a received waveform. Additionally, laser interferometry is expensive and relatively difficult to use in the field. Air-Coupled piezoelectric Transducers offer the strengths of both of these technologies and the weaknesses of neither, but are notoriously difficult to calibrate for use in nonlinear measurements. This work proposes a hybrid modeling and experimental approach to air-Coupled Transducer calibration and the use of this calibration in a model-based optimization to determine the absolute β parameter of the material under investigation. This approach is applied to aluminum and fused silica, which are both well-documented materials and provide a strong reference for comparison of experimental and modeling results.
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using nonlinear ultrasound to track microstructural changes due to thermal aging in modified 9 cr ferritic martensitic steel
Ndt & E International, 2016Co-Authors: Daniel Marino, Jianmin Qu, Alberto Ruiz, Laurence J. JacobsAbstract:Abstract This research investigates second harmonic generation in Rayleigh surface waves propagating in 9%Cr ferritic martensitic steel. Previous experimental results show that nonlinear ultrasound is sensitive to certain microstructural changes in materials such as those due to thermal embrittlement and precipitation hardening. This research measures the ultrasonic nonlinearity parameter as an indicator of microstructural changes due to thermal aging in 9%Cr ferritic martensitic steel specimens. The specimens are isothermally aged for different holding periods to induce progressive changes in the microstructure and to obtain different levels of thermal damage. As thermal aging progresses, the existing dislocations are annihilated in the beginning and precipitates are formed; these microstructural evolutions lead to large changes in the measured nonlinearity parameter, β. Nonlinear ultrasonic experiments are conducted for each specimen using a wedge Transducer for generation and an air-Coupled Transducer for detection of Rayleigh surface waves. The amplitudes of the first and second order harmonics are measured as a function of propagation distance, and these amplitudes are used to obtain the relative nonlinearity parameter at different aging stages. A possible scenario for the microstructural evolution during thermal aging is proposed based on the results from the nonlinear ultrasonic measurements, scanning electron microscopy (SEM), and Rockwell HRC hardness. These results indicate a clear trend that the measured nonlinearity parameter is sensitive to variations in dislocation and precipitate density, and thus can be useful in tracking microstructural changes in this material during thermal aging.
