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High temperature piezoelectric materials serving at harsh environment without failure are desired for structural health monitoring and/or non destructive evaluation of the modern aerospace structures at elevated temperatures (above 600°C). In this report, different high temperature piezoelectric crystals, including the langasite (LGS) type crystals and GaPO4 in trigonal system, melilite type and fresnoite...
Scattering problem of SH-waves in anisotropic (orthotropic) half-space with a semi-cylindrical canyon is researched in the present paper. Complex function method and multi-polar coordinate system are adopted to solve the problem of dynamic stress concentration. According to the boundary condition of the inclusion and the canyon, some examples about dynamic stress concentration factor around the inclusion...
In this paper, two methods based on longitudinal vibration testing of a thin bar are proposed for measuring the dynamic parameters of the viscoelastic materials in a wide frequency region. First, an inverse method by FEM based on resonance measurement is presented, in which the measured response of longitudinal vibration is asymptotically approached by the forward calculated response from the finite...
Based on the electromechanical equivalent circuit method, with the consideration of mechanical loss and dielectric loss, input electrical impedance equation and electroacoustic efficiency equation are obtained. Sandwich piezoelectric transducers of both symmetrical and asymmetrical structure are analyzed. Characteristic parameters of effective electromechanical coupling coefficient, mechanical quality...
Thickness-extensional vibration of a rectangular piezoelectric thin film filter symmetrically covered with two driving electrodes was studied in this paper. The Tiersten and Stevens scalar equation was employed. The Ritz method based on the variational formulation constructed in our previous work was used with trigonometric series as basis functions. Free vibration modes and corresponding resonant...
The design of lever amplification mechanism plays the crucial rule in the performance of double-feet piezoelectric linear motor which is based on the lever amplification principle. The kinematic principle of double-feet piezoelectric linear motor based on the lever amplification mechanism was analyzed and the dynamic model of the lever amplification mechanism based on the flexure hinge was established...
The realization of automatic frequency tracking is of great significance in ultrasonic transducer due to its wide application area in nowadays industrial manufacture. However, excessive overshoot current, serious overheating and long response time remain the urgent issue. To tackle these existing ultrasonic frequency tracking problem, this paper proposes a hybrid technique that integrates fuzzy control...
The 1–3 orthotropic polymer/cement based piezoelectric composite(OPCM) fabricated using PZT-51 as functional part and epoxy resin/cement as matrix via twice cutting-filling methods was to be used as acoustic emission (AE) sensors. The acoustic emission signals were collected by pencil lead-break as signal source on the concrete surface and the linear location test of signal source was carried by AE...
The defect imaging by guided waves in layered plate is always an attractive project in non-destructive testing. The aim of this paper is to study the topological imaging theory and to determine whether it is possible to give the locations of all the defects in layered plate. A two-layered plate consist of aluminum and steel is considered. First, the formulas of the topological gradient are deduced...
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