2017 journal article
Piezoelectric Floating Element Shear Stress Sensor for the Wind Tunnel Flow Measurement
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, 64(9), 7304–7312.
author keywords: Bimorph piezoelectric (PE) structures; electromechanical symmetry; floating element (FE); PMN-33% PT crystal; shear stress
TL;DR:
An analytical model was proposed based on cantilever beam theory with an end-tip-mass for verifying the resonance frequency shift in static stress measurements and the signal-to-noise ratio (SNR) and ambient vibration-filtered pure shear stress sensitivity were obtained through signal processing.
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Source: Web Of Science
Added: August 6, 2018
A piezoelectric (PE) sensor with a floating element was developed for direct measurement of flow induced shear stress. The PE sensor was designed to detect the pure shear stress while suppressing the effect of normal stress generated from the vortex lift up by applying opposite poling vectors to the PE elements. During the calibration stage, the prototyped sensor showed a high sensitivity to shear stress (91.3 ± 2.1 pC/Pa) due to the high PE coefficients (<inline-formula><tex-math notation="LaTeX">$d_{{31}}=- $</tex-math></inline-formula>1330 pC/N) of the constituent 0.67Pb(Mg<inline-formula><tex-math notation="LaTeX">$_{1/3} $</tex-math></inline-formula>Nb<inline-formula> <tex-math notation="LaTeX">$_{2/3} $</tex-math></inline-formula>)O<sub>3</sub>–0.33PbTiO<sub>3</sub> (PMN–33%PT) single crystal. By contrast, the sensor showed almost no sensitivity to normal stress (less than 1.2 pC/Pa) because of the electromechanical symmetry of the sensing structure. The usable frequency range of the sensor is up to 800 Hz. In subsonic wind tunnel tests, an analytical model was proposed based on cantilever beam theory with an end-tip-mass for verifying the resonance frequency shift in static stress measurements. For dynamic stress measurements, the signal-to-noise ratio (SNR) and ambient vibration-filtered pure shear stress sensitivity were obtained through signal processing. The developed PE shear stress sensor was found to have an SNR of 15.8 ± 2.2 dB and a sensitivity of 56.5 ± 4.6 pC/Pa in the turbulent flow.