Search results for "piezoelectricity"

High-velocity Impact Location on Aircraft panels Using Macro-fiber Composite piezoelectric Rosettes

2010

In this article, an approach based on an array of macro-fiber composite (MFC) transducers arranged as rosettes is proposed for high-velocity impact location on isotropic and composite aircraft panels. Each rosette, using the directivity behavior of three MFC sensors, provides the direction of an incoming wave generated by the impact source as a principal strain angle. A minimum of two rosettes is sufficient to determine the impact location by intersecting the wave directions. The piezoelectric rosette approach is easier to implement than the well-known time-of-flight-based triangulation of acoustic emissions because it does not require knowledge of the wave speed in the material. Hence, th…

On the dynamic behavior of piezoelectric active repair by the boundary element method

2011

The dynamic behavior of piezoelectric active repair bonded on cracked structures is analyzed in this article. The boundary element code used to perform the simulations is implemented in the framework of piezoelectricity in order to model the coupling between the elastic and the electric fields, which represents the most important feature of piezoelectric media. The fracture mechanics problem, i.e. the crack, as well as the bonding layer between the host structure and the active patch is modeled by means of the multidomain technique provided with an interface spring model. More particularly, the spring interface model allows considering the bonding layer as a zero-thickness elastic ply char…

1990

Design and fabrication of an acoustic micromixer for biological media activation

2014

International audience; The bioassay of infinitesimal quantities of protein markers in biological samples is the way to early cancer detection. However, this detection can be limited by the diffusion of these macromolecules (analytes) from the bulk to the sensor chip (surface of ligands). Here, we propose a new method to overcome this drawback by the activation of the biological media during the detection step. The principle consists in using ultrasonic vibrations in order to disrupt the equilibrium states of such biomolecular reactions and performing simultaneous detection inside an acoustic micromixer. Technological realization and initial characterizations of the device have been perform…

Ferroelectric-based nanocomposites : towards multifunctional materials

2007

Nanoparticle technologies open the routes for nanostructured materials which combine individual physical properties or generate new functions. In the field of ferroelectric materials the development of dense nanocomposites requires breakthroughs in the elaboration step. Here, we propose a flexible process to obtain ferroelectric−magnetic nanostructured materials using the assembly of superparamagnetic nanoparticles around ferroelectric cores. The appropriate shaping and sintering of these nanocomposites called nanoraspberries enables a tuning of the physical properties of the resulting dense composite:  coexistence between ferroelectricity, piezoelectricity, and superparamagnetism is clearl…

Modeling the electromechanical impedance technique for the assessment of dental implant stability

2015

We simulated the electromechanical impedance (EMI) technique to assess the stability of dental implants. The technique consists of bonding a piezoelectric transducer to the element to be monitored. When subjected to an electric field, the transducer induces structural excitations which, in turn, affect the transducer's electrical admittance. As the structural vibrations depend on the mechanical impedance of the element, the measurement of the transducer's admittance can be exploited to assess the element's health. In the study presented in this paper, we created a 3D finite element model to mimic a transducer bonded to the abutment of a dental implant placed in a host bone site. We simulate…

On the Relationship between Jetted Inks and Printed Biopatterns:Molecular-Thin Functional Microarrays of Glucose Oxidase

2009

Arrays of circular spots of glucose oxidase have been obtained on functionalized silicon oxide by piezoelectric inkjet printing and the enzymatic activity toward glucose recognition has been monitored. The addition of glycerol to the molecular ink allows to obtain high spot definition and resolution (tens of micrometers wide; one molecule tall), but in spite of its well-known structural stabilizing properties, in dynamic conditions it may lead to increased protein stresses. The jetting voltage and pulse length have been found to be critical factors for both activity retention and pattern definition. High voltages and pulse lengths results in stress effects along with the loss of activity, w…

Modeling and Experimental Verification of Ultrasound Transmission in Electro Insulation Oil

2012

A verification study of ultrasound transmission numerical simulation results with experiment results is presented in this paper. The work considers a model of a transformer tank which is filled with electro insulating oil. In the experiment, performed under laboratory conditions, an ultrasound wave is generated by a piezoelectric transducer that is fixed in the centre of the tank and measured by another transducer mounted inside the tank at three distances: 10, 20 and 30 cm from the sound source. The transducer is able to measure and generate acoustic waves in the ultrasound frequency band up to 1 MHz. The simulation considers numerical calculation of acoustic pressure distribution inside t…

Grain size effect and local disorder in polycrystalline relaxors via scanning probe microscopy

2007

Local piezoresponse of individual grains in polycrystalline Pb0.9125La0.0975(Zr0.65Ti0.35)0.976O3 (PLZT 9.75/65/35) relaxor ceramics is studied using the scanning probe microscopy (SPM) technique. The observed piezoelectric contrast consisting of irregular (labyrinth-type) polarization patterns is attributed to the compositional disorder and consequent charge imbalance caused by high La concentration. A measure of this disorder, the polarization correlation length ξ, is directly determined using an autocorrelation analysis function implemented in the SPM software. The analysis of the obtained images shows that ξ taken at the scale ~200 nm varies as a function of the position inside the grai…

On Energy Harvesting Using Piezoelectric Transducer with Two-Port Model Under Force Excitation

2019

Piezoelectric (PE) materials are functional materials that can be used for transforming mechanical stress into electrical energy, that can then be stored and used for powering other devices. In this paper, we provide experimental investigation of PE transducers used for energy harvesting under external force-controlled excitation. The lumped parameter electromechanical model (LPEM) has been assumed and brought into a generalized two-port network notation. Laboratory experiments using a universal test machine (UTM) were performed and used for the parameter identification of the model. The two-port model formulation is validated by comparing results of numerical simulations and experimental d…