Walid Larbi

Structural-Acoustic Vibration Reduction Using Switched Shunt Piezoelectric Patches: A Finite Element Analysis

In this paper, we present a finite element formulation for vibration reduction in structural-acoustic systems using passive or semipassive shunt techniques. The coupled system consists of an elastic structure (with surface-mounted piezoelectric patches) filled with an inviscid linear acoustic fluid. An appropriate finite element formulation is derived. Numerical results for an elastic plate coupled to a parallelipedic air-filled interior acoustic cavity are presented, showing the performances of both the inductive shunt and the synchronized switch shunt techniques.

Dissipative Interface Modeling for Vibroacoustic Problems - A New Symmetric Formulation

This work concerns the variational formulation and the numerical computation of vibroacoustic interior problems with interface damping. The coupled system consists of an elastic structure (described by a displacement field) containing an inviscid, compressible and barotropic fluid (described by a pressure field), gravity effects being neglected. Within the context of noise reduction techniques, we propose to investigate the effect of introducing a thin layer of damping material at the fluid-structure interface. The originality of this work lies in the introduction of an additional unknown field at the fluid-structure interface, namely the normal fluid displacement field [1,2]. With this new scalar unknown, various interface damping models can be introduced in the variational formulation. Moreover, the associated finite element matrix system can be solved in frequency and time domains. Here, a Kelvin-Voigt rheological model is used to take into account the interface damping. For a given material, the damping parameters can be found from the experimental acoustic impedance in a particular frequency range [3]. Following the procedure developed in [4], the proposed variational formulation is written in a symmetric form through the introduction of a displacement potential of the fluid. Numerical examples are presented in order to validate and analyze the new formulation.

Experimental and Numerical Analysis of Sound Transmission Loss Through Double Glazing Windows

The domestic windows in the exterior building facade play a significant role in sound insulation against outdoor airborne noise. The prediction of their acoustic performances is classically carried out in laboratory according to standard ISO 10140. In this work, a 3D elasto-acoustic finite element model (FEM) is proposed to predict the sound reduction index of three different glazing configurations of domestic window follows the ISO recommendations for acoustic measurements, which are compared to laboratory measurements. Two acoustic cavities with rigid-boundaries on both sides of the window are used to simulate respectively the diffuse sound field on the source side and the pressure field on the receiver one. By using a simplified FEM for the double-glazed windows, the sound reduction index is calculated from the difference between the source and receiving sound pressure levels in the one-third octave band from 100 to 500 Hz. Although the comparison between numerical and experimental results shows a relatively good agreement which highlights the interest of this kind of approaches to avoid expensive experiments, many improvements should be taken to ameliorate the model such as the different components of the frame and the design of the two rooms to avoid the problematic of multi-resonant frequency ranges.

Sensitivity Analysis of Frequency Response Functions for Load Resistance of Piezoelectric Energy Harvesters

Piezoelectric energy harvesting from ambient energy sources, particularly vibrations, has attracted considerable interest throughout the last decade. Sensitivity analysis is a promising method used for many engineering problems to assess input-output systems based on vibration. In this paper, the formulation of first order sensitivity (FOS) of complex Frequency Response Functions (FRFs) is developed to evaluate the output responses of piezoelectric energy harvesters. The adapted approach for the FOS is the finite difference method, which consists in computing an approximation of the first derivation. Furthermore, the main goal is to study the influence of the variation of the load resistance from the short circuit (load resistance tends to zero) to open circuit (load resistance tends to the infinity) conditions on the tip displacement and the voltage FRFs of a Bimorph Piezoelectric Energy Harvester (BPEH). The determination of FRFs of the harvester are derived using Finite Element Modelling for a bimorph piezoelectric cantilever beam based on Euler-Bernoulli theory, which is composed of an aluminum substrate covered by two PZT-5A layers. The results show a high sensitivity of the FRFs of the BPEH to the load resistance at the natural frequencies. For each excitation frequency, the sensitivity near the resonance frequencies decreases from the short circuit conditions to the open circuit conditions.

Finite Element Modeling and Analysis of a Bimorph Piezoelectric Energy Harvester

In the last few years, energy harvesting using piezoelectric materials has become a popular research topic because of its efficiency for converting vibration energy into electrical energy. In previous research studies, the shape and size of the harvester have been optimized for maximum power output density using analytical, numerical, and experimental approaches. This paper presents a finite element model of a bimorph piezoelectric energy harvester. The model is used to study the effect of load resistance on the resonant frequency and the generated power. The harvester consists of a clamped-free composite cantilever beam composed of an elastic substructure bracketed by two identical piezoelectric layers which are connected to a resistive load. An electromechanical finite element formulation for the dynamic analysis of the problem is first presented. The associated variational formulation is written in terms of structure displacement and electric potential in the piezoelectric layers. The finite element model of the bimorph energy harvester has been implemented on COMSOL Multiphysics software. It has been concluded that the energy harvester generates a maximum of electrical power output when the structure vibration matches the first natural frequency of the harvester and the optimal resistance load is connected to the piezoelectric layers.

Coupled Finite Element-Boundary Element Formulation for Noise and Vibration Attenuation Using Shunt Piezoelectric Materials

In this paper, we present a coupled finite element/boundary element method (FE/BE) for control of noise radiation and sound transmission of vibrating structure by active piezoelectric techniques. The system consists of an elastic structure (with surface mounted piezoelectric patches) coupled to external/internal acoustic domains. The passive shunt damping strategy is employed for vibration attenuation in the low frequency range.

Absorbing interfaces in structural-acoustic coupled problems

This work concerns finite element formulations of structural-acoustic interior problems with dissipative interfaces. The main purpose is to establish the link between wall acoustic impedance models and poroelastic appraoches based on the Biot theory. The proposed method consists in determining the acoustic impedance parameters starting from intrinsic characteristics of the porous medium. This impedance is then introduced into the vibroacoustic finite element formulation to take into account the dissipative aspect of the fluid-structure interface.

Formulation éléments finis de problèmes élastoacoustiques avec interface dissipative

Dans cet article, on présente une nouvelle formulation éléments finis pour les problèmes d’élastoacoustique avec interface dissipative. L’approche proposée est basée sur l’introduction du champ de déplacement normal du fluide au niveau des interfaces dissipatives ce qui permet de transposer les formulations du domaine fréquentiel au domaine temporal lorsque le fluide est décrit par un champ scalaire comme la pression. Deux modèles d’amortissement pour prendre en compte l’effet dissipatif de l’interface sont présentés: le modèle de Kelvin-Voigt avec l’aspect symétrisation du problème et celui de Zener. L’effet amortissant de l’interface est analysé sur des exemples simples dans les domaines fréquentiel et temporel.