Piezoelectric d_(15) shear response-based torsion actuation mechanism:an experimental benchmark and its 3D finite element simulation

An experimental benchmark is proposed for piezoelectric,direct-torsion actuation using mono-morph piezoceramic d_(15)shear patches.This is reached by designing and assembling an adaptive plate having two identical composite faces sandwiching a core made of connected six oppositely polarized(OP)piezoceramic d15 shear patches along the length.An electronic speckle pattern interferometry system was used to measure the static tip deflection of the adaptive sandwich composite plate that was mounted in a cantilever configuration and actuated in torsion by progressively applied voltages on the piezoceramic shear core electroded major surfaces.Then,the effective rate of twist was post-processed and proposed as an evaluation criterion for smart composites under piezoelectric torsion actuation.For verification of the experimental results,the proposed experimental benchmark was simulated using three-dimensional piezoelectric finite elements(FE)within ABAQUS®commercial software.The comparison of the obtained experimental and simulation results showed reasonable agreement,but the slight nonlinear experimental response was not confirmed by the linear FE analysis.The experimentally proved torsion actuation mechanism,produced by OP piezoceramic d15 shear patches,can be applied actively to prevent torsion in many applications,such as in wind turbines,helicopter blades,robot arms,flexible space structures,etc.

Field-dependent nonlinear piezoelectricity:a focused review

This contribution presents a multidisciplinary review of the so-called field-dependent nonlinear piezoelectricity.It starts with an introduction that poses the literature analysis framework,through defining this operational(that is oftenmet in practice)piezoelectric field-dependent nonlinearity.Indeed,the latter is a less known phenomenon although it is inherent to stress-free actuation responses of corresponding smart materials,actuators and structures.Then,related experimental observations from piezoelectric materials,actuator devices and smart structures tests are multidisciplinary surveyed for understanding the underlying mechanisms of the encountered field-dependent nonlinearity.Next,empirical material and numerical structural modelling and simulation approaches are critically reviewed from,respectively,the constitutive and finite element analysis points of view.Summary conclusions and few future directions for research are finally provided as a closure.It is worth mentioning that,although it is concise(retains only experiments and experimentally-correlated models and simulations),this critical review covers the last three decades period which is almost the whole age of the piezoelectric materials,actuators and smart structures research field.

Analysis of the sensitivity to pressure and temperature of a membrane based SAW sensor

This paper presents a FEM analysis of a membrane-based Surface Acoustic Wave(SAW)sensor.The sensor is a 2.45GHz Reflective Delay Line(R-DL)based on Lithium Niobate(LiNbO_(3)).As the wave propagation time is much smaller than the typical time constant of the phenomena to be monitored(deformation,temperature change etc.),the analysis can be performed in three successive steps.First,a static FEM study of the complete sensor(housing included)is carried out,to compute the temperature,stress and strain fields generated in the sensitive area by the measured parameters(pressure,temperature,etc.).Then,a dynamic electro-mechanical study of the R-DL is performed.The simulation takes the previously computed fields into account,which makes it possible to compute the sensor sensitivity to the measured parameters.The model takes advantage of the periodicity of the components of the R-DL to compute phenomenological parameters(Coupling-of-Mode parameters),which can later on be used to compute the electrical response of the sensor(step 3).In this paper,we focus on the first two steps.The COM parameters are extracted,under simultaneous thermal and mechanical stresses.Especially,the sensor sensitivity is obtained from the evolution of the velocity,under various stress configurations.

Piezoelectric d_(15) shear-response-based torsion actuation mechanism:An exact 3D Saint-Venant type solution

This paper is concerned with the detailed analysis of the behavior of a piezoceramic bi-morph torsion actuator using the d_(15)-effect.The bi-morph actuator is made of two oppositely polarized adjacent piezoceramic prismatic beams.The mathematical analysis is based on the Saint-Venant torsion theory;a formulation of the electromechanically coupled problem in terms of a stress function and of the electric potential is derived,which represents an exact solution of a specific three-dimensional problem;in particular,for the case when the axial stress and the axial component of the electric displacement vector are independent of the axial coordinate.The resulting boundary-value problem in the cross-section is solved using the method of finite differences.Solutions for the actuated rate of twist are presented and compared to three-dimensional electromechanically coupled finite element solutions using ABAQUS®for the case of a cantilevered bi-morph actuator.A very good agreement is found.

Smart structures,materials and nano technology in engineering

Smart materials are active materials that are nowadays commonly used for sensing,actuation,and transduction for structural noise(acoustic),shape(morphing)and vibration control and health monitoring of(in historical order)offshore petroleum,aerospace,aeronautic,mechanical,civil(including infra-structures and wind turbines)and biomedical engineering.More recently,they were also used for energy harvesting from environment for autonomously and wirelessly powering of various temperature or pressure monitoring sensors and some medical(fluidic)implants and(surgery)devices.

Static experimentations of the piezoceramic d_(15)-shear actuation mechanism for sandwich structures with opposite or same poled patches-assembled core and composite faces

Static d_(15)-shear actuated smart composites consisting of glass fiber/epoxy layers sandwiching piezoceramic shear patches-assembled cores were investigated experimentally and numerically.The piezoceramic cores were formed by connecting two or three patches with the same or opposite polarization directions.For each cantilevered benchmark the shear-induced transverse tip deflection,under increasing actuation voltage,ranging from 61.5 V to 198 V,was measured by an electronic speckle pattern interferometer system.The performance of the shear actuated smart composites was characterized by their shear-induced transverse deflection per length per voltage.It was found that this performance is much better at high voltages for which the response becomes nonlinear.For verification of the experimental results the proposed benchmarks were simulated within ABAQUS®commercial code using three-dimensional piezoelectric finite elements.The comparison of the obtained experimental and simulation results show a nonlinear dependence of the transverse deflection for voltages higher than around 92 V.