Analyses of the anisotropic behavior of a Uber composite plate from the laser-generated ultrasonic Lamb waveforms propagating in different directions are presented by employing wavelet transform techniques.The time-fr...Analyses of the anisotropic behavior of a Uber composite plate from the laser-generated ultrasonic Lamb waveforms propagating in different directions are presented by employing wavelet transform techniques.The time-frequency representation plots of the waveforms clearly exhibit the anisotropic behavior of the composite plate.The plots also indicate that the waveform mainly consists of three or four lower-order Lamb wave modes,and other higher-order modes can be neglected in extracting elastic stiffness properties by comparison of theory with experimental waveforms.The group velocity of each mode is calculated according to the group delay and the source-receiver distance.展开更多
The microstructure effect of ultrasonic waves in a unidirectional titanium graphite composite is analyzed by the mode energy conversions of the laser-generated ultrasonic Lamb wvaves.The carrying energy of each mode i...The microstructure effect of ultrasonic waves in a unidirectional titanium graphite composite is analyzed by the mode energy conversions of the laser-generated ultrasonic Lamb wvaves.The carrying energy of each mode in the Lamb wvaves is calculated quantitatively by the time-frequency filtering technique of the Wigner distribution.We found that the energy conversions among modes have happened in the process of propagation of ultrasonic Lamb wave.These energy conversions are attributed to microstructure scattering of ultrasonic wave by the fibers in a fiber reinforced composite material.This work will provide a quantitative method of ultrasonic characterizationof microstructure feature of the composite materials by the laser-generated Lamb wave technique.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No.19574024the Natural Science Foundation of Jiangsu Province under Grant No.BK97031。
文摘Analyses of the anisotropic behavior of a Uber composite plate from the laser-generated ultrasonic Lamb waveforms propagating in different directions are presented by employing wavelet transform techniques.The time-frequency representation plots of the waveforms clearly exhibit the anisotropic behavior of the composite plate.The plots also indicate that the waveform mainly consists of three or four lower-order Lamb wave modes,and other higher-order modes can be neglected in extracting elastic stiffness properties by comparison of theory with experimental waveforms.The group velocity of each mode is calculated according to the group delay and the source-receiver distance.
基金Supported by the National Natural Science Foundation of China under Grant No.19974017and the Doctoral Foundation of the Education Ministry of China under Grant No.1999028432.
文摘The microstructure effect of ultrasonic waves in a unidirectional titanium graphite composite is analyzed by the mode energy conversions of the laser-generated ultrasonic Lamb wvaves.The carrying energy of each mode in the Lamb wvaves is calculated quantitatively by the time-frequency filtering technique of the Wigner distribution.We found that the energy conversions among modes have happened in the process of propagation of ultrasonic Lamb wave.These energy conversions are attributed to microstructure scattering of ultrasonic wave by the fibers in a fiber reinforced composite material.This work will provide a quantitative method of ultrasonic characterizationof microstructure feature of the composite materials by the laser-generated Lamb wave technique.
