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Generation of narrowband Lamb waves based on the Michelson interference technique

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Chinese Physics B 2018年第5期27卷 328-333页

作者： Tian-Ming Ye Yan-Feng Xu Wen-Xiang Hu Institute of Acoustics Tongji University Shanghai 200092 China

An optical method of generating narrowband Lamb waves is presented. It is carried out with a laser line array in a thermoelastic regime implemented by the Michelson interference technique, where the formed array element spacing can be flexibly and conveniently changed to achieve selective mode excitation. In order to simulate the displacement response generated by this array, its intensity distribution function is presented to build a theoretical analysis model and to derive the integral representation of the displacement response. The experimental device and measuring system are built to generate and detect the Lamb waves on a steel plate. Numerical calculation results of narrowband Lamb wave displacement signals based on the theoretical model show good agreement with experimental results.

关键词： narrowband Lamb wave selective generation laser array laser ultrasonics

Effect of optical penetration on laser generatedthermoelastic ultrasound in solids

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Chinese Journal of Acoustics 1995年第4期14卷 289-299页

作者： FANG Qiping BAI Yuhai and C. F. Ying(Institute of Acoustics, Academia Sinica. Beijing 100080)

The effect of optical penetration on laser thermoelastically-generated ultrasound in non-metallic solids is studied theoretically on the basis of the thermoelastie equations. In one-dimensional model, on the assumption of some finite laser penetration, the general expression of wave displacement is obtaincd by solving the thermal diffusion and thermoelastic displacement equations, from which the influencc of optical absorption on the displacement amplitude is analyzed. In the case of two-dimensional axial symmetry, on neglecting the thermal diffusion, we solve the thermoelastic wave equation by means of the integral transform method and obtain analytic expressions of the wave displacement components in the *** patterns of both longitudinal and shear waves are presented and discussed.

关键词： laser ultrasonics Thermoelastic generation Optical penetration Directivity

Experimental Set-up of laser Ultrasonic Techniques and Applications

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Tsinghua Science and Technology 1997年第2期2卷 62-66页

作者：周辛庚何存富

A laser ultrasonics generation and non contact detection system has been developed. The weak generated ultrasonic signal of nanosecond duration and nanometer amplitude can be detected with a confocal Fabry Perot interferometer (CFPI). It can be applied to determination of elastic constants of material and flaw detection. The experimental results show that laser ultrasonic technique is practical and effective.

关键词： laser ultrasonics non destructive testing elastic constants flaw detection

THEORY ON THE laser EXCITED WAVE PROPAGATION IN A SINGLE PIEZOELECTRIC PLATE UNDER A BIAS ELECTRIC FIELD

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THEORY ON THE LASER EXCITED WAVE PROPAGATION IN A SINGLE PIE...

FINITE ELEMENT MODELING OF laser GENERATED ULTRASOUND IN BLACK PDMS MATERIALS

2012全国压电和声波理论及器件技术研讨会

作者： Gen CHEN Yong-dong PAN Zheng ZHONG Institute of Acoustics Tongji University School of Aerospace Engineering and Applied Mechanics Tongji University

The laser excited wave propagation in a single piezoelectric plate under a bias electric field is studied *** state vector approach is used to derive the differential equations for the piezoelectric plate under a bias electric *** laser is modeled as a transient force at the *** solving the state space equation,both the dispersion curves and surface displacement of the epicenter of the single piezoelectric plate under the laser ablation excitation with bias electric field are *** is found that the wave propagation in the piezoelectric is influenced by the bias electric *** numerical calculation shows that along the polarization direction,the velocity of the acoustic wave in the piezoelectric plate with positive bias electric field is larger than that without any electric field,which is just an inversed situation in the negative *** theoretical findings will provide the basis for the further experimental investigation.

关键词： Piezoelectric plate laser ultrasonics Bias field Active control

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FINITE ELEMENT MODELING OF LASER GENERATED ULTRASOUND IN BLA...

laser ultrasonic technique for surface defects detection of 6061 aluminum alloy

2015全国压电和声波理论及器件技术研讨会

作者： Kun-lun DENG Hong-lang LI Wei LUO Ya-bing KE Shi-tang HE Institute of Acoustics Chinese Academy of Sciences Huazhong University of Science and Technology

Carbon black combined PDMS is a promising material for laser ultrasonic inspection but the generated ultrasound field characteristics have not been *** obtain the wave field generated by laser in the polymer material,thermo-elasticity model was adopted,a 2D axial symmetry finite element model is built and the physics and parameters are set as actual situation for ultrasonic wave *** generated acoustic wave modes and the transient wave field are *** multi-mode wave field and the directivity and intensity of generated ultrasonic are *** calculation results show that the polymer combined carbon black material has a great prospect in nondestructive detecting applications.

关键词： laser ultrasonics Finite element method Acoustic field

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Journal of Measurement Science and Instrumentation 2019年第3期10卷 293-298页

作者： LI Hai-yang WEI Zhuang-zhuang PAN Qiang-Hua School of Information and Communication Engineering North University of China Taiyuan 030051 China China Special Equipment Inspection and Research Institute Beijing 100029 China

In order to estimate and detect the surface defect depth of metals, the transmission method of laser ultrasonic surface waves is used in this work. The laser ultrasonic detection platform taking use of thermoelastic mechanism as acoustic signal excitation method and interference receiver as acoustic signal receiver method was built, by which B-scan images of detected specimens with surface defects were collected to establish the relationship between the transmission coefficient and depth of the surface defect. Experimental results show that the amplitude of transmitted acoustic signal is related to the depth of surface defect. At last, a fitted curve of transmission coefficient using measured experimental data is obtained to estimate depth of surface defect on the 6061 aluminum alloy. Furthermore, a surface defect depth of 0.3 mm is estimated by the fitting curve with an estimated error of 16%. Therefore, a experimental method using the transmission method by laser ultrasonic is presented in this paper.

关键词： laser ultrasonics transmission method surface defect depth detection

DEPTH PROFILING OF COATING BY laser ULTRASONIC TECHNIQUE

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DEPTH PROFILING OF COATING BY LASER ULTRASONIC TECHNIQUE

laser-GENERATED LAMB WAVES INSIDE AN ALUMINUM PLATE:COMPARISON BETWEEN THEORY AND EXPERIMENT

2012全国压电和声波理论及器件技术研讨会

作者： Xue-hang SONG Yong-dong PAN Zheng ZHONG Kao-shan DAI School of Aerospace Engineering and Applied Mechanics Tongji University School of Civil Engineering Tongji University

Functionally graded materials（FGMs） show great potential,and the development of new FGMs will lead to materials that have properties not achievable with homogeneous *** dispersion curves of surface acoustic wave propagating in coating structures are investigated using the reflection and transmission coefficient ***’s found that the dispersion curves are sensitive to the transverse wave velocity,but they are not very sensitive to the longitudinal wave velocity and *** algorithms adopted to handle the inverse *** object function is established based on experimental phase velocity and the theoretical *** reconstructed depth-profiling of material properties agrees well with the experimental ones.

关键词： Coating laser ultrasonics Inverse problem Genetic algorithm

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LASER-GENERATED LAMB WAVES INSIDE AN ALUMINUM PLATE:COMPARIS...