By using a Q-switched YAG laser and an optical path delay set-up,we study the process in which a Jaser induces breakdown to produce plasma in air,and obtain time-resolved Mach-Zehnder interferograms and opt ical sh ad...By using a Q-switched YAG laser and an optical path delay set-up,we study the process in which a Jaser induces breakdown to produce plasma in air,and obtain time-resolved Mach-Zehnder interferograms and opt ical sh adowgrams of the initial stage of the plasma and the expansion wave produced in the process for the first time.展开更多
A Q-switched YAG laser is used to act repeatedly upon a charge-coupled devices(CCD)having metal-oxide-semiconductor structure,and plasmas in the process are investigated by a Mach-Zehnder interferomcter.According to t...A Q-switched YAG laser is used to act repeatedly upon a charge-coupled devices(CCD)having metal-oxide-semiconductor structure,and plasmas in the process are investigated by a Mach-Zehnder interferomcter.According to the production and development of the plasmas,the damage mechanism of the optoelectronic device is analyzed.展开更多
This research focuses on measuring the mode transformation and energy attenuation of wedge waves for different apex angle wedges by using laser ultrasound techniques.Pulsed laser excitation and optical deflection beam...This research focuses on measuring the mode transformation and energy attenuation of wedge waves for different apex angle wedges by using laser ultrasound techniques.Pulsed laser excitation and optical deflection beam methods for detection were used to measure the wedge waves.In experiment,various wedge waves at different locations were recorded by scanning the excitation laser along the wedge tip,and different orders of wedge waves were observed.By fixing the distance between the excitation and detection positions and scanning the samples along the direction normal to the wedge tip,the modes transformation process was obtained.It was found that the energy of the acoustic waves for 20°,25° and 30° wedges decreased exponentially to a steady energy of Rayleigh wave within the main wavelength range of the acoustic modes,while the energy of acoustic waves of 45° and 60° wedge remained stable as the propagation line was scanned away from the wedge tip.展开更多
Based on the thermoelastic mechanism of laser ultrasonic, the problems of the thermal conduction and the coupling between the motion of solid and fluid are solved by using the finite element method. And then the trans...Based on the thermoelastic mechanism of laser ultrasonic, the problems of the thermal conduction and the coupling between the motion of solid and fluid are solved by using the finite element method. And then the transient waveforms of leaky Lamb waves induced by pulse laser action on the air-aluminum interface are obtained. Experimental signals of laser-induced leaky Lamb waves at the air-alu- minum interface are detected by applying an our-developed detector, based on the light deflection principle. The dispersion and attenuation properties of leaky Lamb waves are analyzed through the phase spectral analysis.展开更多
文摘By using a Q-switched YAG laser and an optical path delay set-up,we study the process in which a Jaser induces breakdown to produce plasma in air,and obtain time-resolved Mach-Zehnder interferograms and opt ical sh adowgrams of the initial stage of the plasma and the expansion wave produced in the process for the first time.
文摘A Q-switched YAG laser is used to act repeatedly upon a charge-coupled devices(CCD)having metal-oxide-semiconductor structure,and plasmas in the process are investigated by a Mach-Zehnder interferomcter.According to the production and development of the plasmas,the damage mechanism of the optoelectronic device is analyzed.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60878023 and 61108013)the program for New Century Excellent Talents in University (NCET)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘This research focuses on measuring the mode transformation and energy attenuation of wedge waves for different apex angle wedges by using laser ultrasound techniques.Pulsed laser excitation and optical deflection beam methods for detection were used to measure the wedge waves.In experiment,various wedge waves at different locations were recorded by scanning the excitation laser along the wedge tip,and different orders of wedge waves were observed.By fixing the distance between the excitation and detection positions and scanning the samples along the direction normal to the wedge tip,the modes transformation process was obtained.It was found that the energy of the acoustic waves for 20°,25° and 30° wedges decreased exponentially to a steady energy of Rayleigh wave within the main wavelength range of the acoustic modes,while the energy of acoustic waves of 45° and 60° wedge remained stable as the propagation line was scanned away from the wedge tip.
文摘Based on the thermoelastic mechanism of laser ultrasonic, the problems of the thermal conduction and the coupling between the motion of solid and fluid are solved by using the finite element method. And then the transient waveforms of leaky Lamb waves induced by pulse laser action on the air-aluminum interface are obtained. Experimental signals of laser-induced leaky Lamb waves at the air-alu- minum interface are detected by applying an our-developed detector, based on the light deflection principle. The dispersion and attenuation properties of leaky Lamb waves are analyzed through the phase spectral analysis.
