This article aims to develop a pressure sensing method by utilizing both a contacting active sensor and a non-contacting laser ultrasound transmitter. An overloaded stress in an industrial pressure tank such as a nuclear reactor may cause a catastrophic explosion; thus, it is essential to monitor the mechanical stress in a reliable manner for the structural safety. Among many different types of stress sensing methods, ultrasound sensing has been attractive due to its non-invasive measurement feature. For the recent decades, subsurface longitudinal (SSL) ultrasonic wave has been widely used since it is not only less dependent on the internal medium and the surface condition, but also has the fastest wave speed without wave distortion. In our work, laser source and Aluminum nitride (AlN) wafer are used to generate and to receive SSL ultrasonic waves, respectively. In order to increase the photoacoustic efficacy, a composite of carbon-soot nanoparticles (CSNP) and polydimethylsiloxane (PDMS) was attached onto the intermediate wedge at the transmitter side. The photoacoustic experiment results demonstrate a reasonable linear relationship between the stress level and the time-of-flight variation of the propagated wave signal.
This paper presents an experimental and numerical characterization of a piezoelectric d36 shear-based torsion actuator made of xPb(Mg1/3Nb2/3)O3-(1-x)PbTiO3 (PMN-PT) single crystals embedded between Polydimethylsiloxane (PDMS) layers. The generated rate of twist value of the piezoelectric d36-mode PMN-PT single crystal composite torsion actuator was obtained using a laser vibrometer from the maximum detected transverse deflection measurement. The quasi–static torsion actuation experiments were conducted on the piezoelectric d36 torsion actuator by applying different AC voltages at 1 Hz. The experimental benchmark was further modelled by Finite Element (FE) code ABAQUS® using three dimensional (3D) piezoelectric finite elements. The experimental results and Finite Element computations showed good agreement. Findings reveal that more rate of twist is produced by PMN-PT single crystals in comparison to piezoceramic alternatives. This piezoelectric PMN-PT d36-mode composite torsion actuator can be effectively used in torsional deformation control.
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