In this paper a complete multiphysics modelling via the finite element method (FEM) of an air-coupled array of piezoelectric micromachined ultrasonic transducers (PMUT) and its experimental validation are presented. Two numerical models are described for the single transducer, axisymmetric and 3D, with the following features: the presence of fabrication induced residual stresses, which determine a non-linear initial deformed configuration of the diaphragm and a substantial fundamental mode frequency shift; the multiple coupling between different physics, namely electro-mechanical coupling for the piezo-electric model, thermo-acoustic-structural interaction and thermo-acoustic-pressure interaction for the waves propagation in the surrounding fluid. The model for the single transducer is enhanced considering the full set of PMUTs belonging to the silicon dye in a array configuration. The results of the numerical multiphysics models are compared with experimental ones in terms of the initial static pre-deflection, of the diaphragm central point spectrum and of the sound intensity at 3.5 cm on the vertical direction along the axis of the diaphragm.

Viscoplastic constitutive modeling of sintered nano-silver particles: a variable-order fractional model v.s. Anand model 10:20 20mn

In this paper a complete Multiphysics modelling via the Finite Element Method (FEM) of an air-coupled Piezoelectric Micromachined Ultrasonic Transducer (PMUT) is described, with its experimental validation related to the mechanical and acoustic responses.The numerical model takes into account the presence of fabrication induced residual stresses, which determine a non-linear initial deformed configuration of the diaphragm and a substantial frequency shift associated with the fundamental eigenmode of the vibrating system.The complete simulation of the device's behaviour is obtained considering multiple coupling between different fields: electro-mechanical coupling for the piezoelectric model, thermo-acoustic-structural interaction and thermoacoustic-pressure interaction for the waves propagation in the surrounding fluid.The model gives a realistic estimation of the fundamental frequency and of the PMUT's quality factor through the adoption of large deformation analyses and by means of a proper modelling of the air, considering its thermo-viscous properties, that induce the power dissipation in the so-called boundary layer at the fluidstructure interface.The results of the numerical multi-physics model are compared with experimental ones in terms of the initial static pre-deflection, of the membrane center vertical displacement frequency spectrum and of the sound intensity at 3.5 cm on the vertical direction of the axisymmetric axis of the diaphragm.

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This paper presents a numerical reduced-order modeling (ROM) approach for complex multi-layered arrays of piezoelectric micromachined ultrasonic transducers (PMUTs). The numerical modeling technique adopted to generate an array of PMUTs consisting of a considerable number of transducers allows for a large reduction in computational cost without reducing accuracy. The modeling idea is based on coupling shell elements applied to the PMUT structural layers with 3D-solid elements applied to the piezoelectric layer. A set of eigenfrequency and frequency domain analyses are presented considering a single ROM of a PMUT performing in different ambients and the performing central frequencies are obtained for every considered scenario. A unique arrangement of 228 PMUTs is presented and tested for its ability to transmit and receive acoustic waves. The operating frequency band of the array and the level of interference and cross-talk among different PMUTs in the near field are estimated. Finally, the results from a preliminary experimental test performed to analyze the acoustic abilities of an 8 × 8 array of PMUTs are presented. A corresponding numerical model is created and the obtained results matched the experimental data, leading to a validation of the modeling technique proposed in this work.