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The main problem among the developing of the thickness mode piezoelectric air-coupled ultrasonic transducer is the acoustic impedance mismatch between piezoelectric plate and air. To solve this problem, a kind of porous composite material is introduced as the matching layer. The acoustic parameters measurement methods of the hollow glass microspheres filled epoxy resin composite material is studied...
A dynamic photoelastic imaging system is presented and employed to study the directivity of ultrasonic scattering field. Focusing on the cylindrical cavity, photoelastic photograph displays the scattering field, and the directivity patterns of different distances can be plotted by the gray level per pixel. Compared with the simulation results by finite element method (FEM), dynamic photoelastic technique...
The non-collinear mixing method for detection of plastic zone at crack tip is studied in this paper. When stress loaded on crack in solid is more than critical stress, which is related to length of crack, the crack will happen to expend fast leading to material fracture. However, critical stress of crack is affected by plastic zone existence at crack tip, so detection of plastic zone at crack tip...
Numerical modeling for a sandwich dipole well logging transmitting transducer is conducted in this work. The characteristics for the first-order bending vibration of the sandwich transducer within different fluid loads are numerically analyzed. It is found that the resonant frequency and transmitting voltage response level are affected by the density, acoustic velocity and acoustic impedance of the...
Based on the Mason equivalent circuit, a theoretical model of ultrasonic signal generated by controlling the excitation signal has been formulated. Large TBWP (time-bandwidth product) ultrasonic signals can be generated by driving a piezoelectric transducer with modified LFM (linear frequency modulation) signal. Better performances are obtained in the waveform, bandwidth and linear time-frequency...
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