Prediction of the dynamic response of a plate treated by particle impact damper

International audienceIn this paper, an experimental characterisation of a particle impact damper (PID) under periodic excitation is investigated. The developed method allows the measurement of damping properties of PID without the supplementary use of a primary structure. The passive damping of PID varies with the excitation frequency and its design parameters. The nonlinear damping of PID is then interpreted as an equivalent viscous damping to be introduced in a finite element model of a structure to predict its dynamic response. The results of numerical simulations are in good agreement with those of experiment and show the relevance of the developed method to predict the dynamic behaviour of a structure treated by PID's

A robust component mode synthesis method for stochastic damped vibroacoustics

International audienceIn order to reduce vibrations or sound levels in industrial vibroacoustic problems, the low-cost and efficient way consists in introducing visco- and poro-elastic materials either on the structure or on cavity walls. Depending on the frequency range of interest, several numerical approaches can be used to estimate the behavior of the coupled problem. In the context of low frequency applications related to acoustic cavities with surrounding vibrating structures, the finite elements method (FEM) is one of the most efficient techniques. Nevertheless, industrial problems lead to large FE models which are time-consuming in updating or optimization processes. A classical way to reduce calculation time is the Component Mode Synthesis method (CMS), whose classical formulation is not always efficient to predict dynamical behavior of structures including visco-elastic and/or poro-elastic patches. Then, to ensure an efficient prediction, the fluid and structural bases used for the model reduction need to be updated as a result of changes in a parametric optimization procedure. For complex models, this leads to prohibitivenumerical costs in the optimization phase or for management and propagation of uncertainties in the stochastic vibroacoustic problem. In this paper, the formulation of an alternative CMS method is proposed and compared to classical (u,p) CMS method: the Ritz basis is completed with static residuals associated to visco-elastic and poro-elastic behaviors. This basis is also enriched by the static response of residual forces due to structural modifications, resulting in a so-called robust basis, also adapted to Monte Carlo simulations for uncertainties propagation using reduced models

Reduction method applied to viscoelastically damped finite element models

International audienceWe propose in this paper to combine the GHM (Golla-Hughes-Mc Tavish) method with model reduction technique, especially direct condensation methods to resolve the problem of increased model order of viscoelastically structures. In fact, modeling structures using the GHM method leads to global systems of equation of motion whose numbers of degrees-offreedom largely exceeds the order of the associated undamped system. As result, the numerical resolution of such equations can require prohibitive computational (CPU) time. So, to overcome this problem, both Static and Dynamic methods are used to reduce the order of finite elements matrices while preserving its capability to represent the dynamic behavior of viscoelastically damped structures. This paper intends to compare these two methods in direct reduction. Numerical example applied to cantilever beam structure is presented. This example will highlight the domain of validity of the studied methods. Results obtained from these two reduction methods are compared with the full model in order to illustrate its performances and its practical interest in the dynamic analysis of viscoelastically damped structures

Optimisation multi-objectif par l'algorithme des colonies de fourmis

International audienceL'objectif de ce travail est de montrer qu'il est possible de mener l'optimisation multiobjectifs en utilisant un algorithme heuristique aussi performant qu'un Algorithme Génétique (AG), qui est actuellement le plus utilisé dans les solveurs d'optimisation. Il s'agit de l'algorithme d'optimisation basé sur l'approche Pareto (Pareto Ant Colony Optimization : P-ACO). Dans ce papier on montrera à travers l'étude d'une plaque raidie en composite multicouches que l'algorithme P-ACO est aussi performant qu'un AG mais a l'avantage d'être plus aisé à mettre en oeuvre numériquement. La modélisation de la structure composite est réalisée par le code de calcul commercial ANSYS®

Vibration pumping of mdof structures using optimised multiple dynamic absorbers

International audienceThe concept of energy pumping is an innovative dynamic phenomenon; it gives rise to new generation of dynamic absorbers. Theoretical studies and feasibility tests are necessary for better understanding of their dynamic behaviour and to be applied on real structures or machines. In this paper, numerical evidence is firstly given for the passive and broadband targeted energy transfer in the case of a linear system under shock excitation with Multiple Dynamic Absorbers or Nonlinear Energy Sink (NES). Secondly, it is shown that many NES absorb shock energy in only way and dissipate this energy locally, without "spreading" it returns to the linear system. The numerical results of optimisation in the case of NES linked to a linear beam are compared to Tuned Mass Dampers (TMD) linked to the same beam

Caracterisation dynamique et conception robuste d'interfaces de structures

Les structures mécaniques complexes résultent de l assemblage de plusieurs composants, possédant souvent des propriétés mécaniques différentes, reliés à leurs interfaces par différents types de jonctions. L hétérogénéité des comportements dynamiques de ces sous-structures et leurs sollicitations extérieures vont générer des efforts sur la structure principale et des accélérations importantes au niveau des équipements embarqués, affectant leur fonctionnement, leur fiabilité, leur sécurité. Il est alors nécessaire de les protéger en les isolant du reste de la structure.Ces travaux concernent la maîtrise des niveaux vibratoires et visent à fournir une méthode de caractérisation dynamique des interfaces entre différentes sous-structures. Celle-ci est ensuite intégrée dans une démarche visant à minimiser la puissance transmise entre des sous-structures sources et réceptrices.Une méthode de modes de flux de puissance a été développée, dont les valeurs et efforts propres fournissent, respectivement, des informations quantitatives et qualitatives sur les flux de puissance à l intérieur d une structure. Son application à l étude de la puissance transmise entre deux sous-structures permet d identifier les directions et les participations des principaux chemins de puissance transitant par les jonctions.Ces résultats ont été appliqués afin de proposer une méthodologie de conception robuste des interfaces de structures. Deux démarches d optimisation ont été comparées visant à minimiser la puissance transmise par rapport aux paramètres de raideurs des jonctions. L importance de considérer la robustesse de ces solutions a été soulignée par une approche complémentaire non-probabiliste.Complex mechanical structures are composed of an assembly of several components, often exhibiting different mechanical properties and joined at their interfaces by different junction types. The various dynamic behaviours of these substructures and the applied external loadings generate important efforts on the main structure, resulting in high acceleration responses of the on-board equipments, affecting their performance, reliability and security. It is therefore necessary to protect them from these harsh conditions by isolating them from the rest of the structure.These researches are related to structural vibration control and aim at proposing a new method to dynamically characterize interfaces between different substructures. This method is then integrated to a robust design approach to minimize the power transmitted between a source and a receiver substructure. A power flow mode method has been developed, which allows determining eigenvalues and eigenvectors respectively representing qualitative and quantitative information on the power flowing inside the structure. This has been further applied to study the power transmitted at the interface, making it possible to identify the direction associated to the dominant power flow pattern and to quantify their contribution.These results have been applied to propose a robust design approach of structural interfaces. Optimization procedures have been implemented and compared to minimize the power transmitted between with respect to the interface stiffness parameters. The importance of considering the robustness of these solutions has been underlined by performing a complementary analysis based on a non-probabilistic approach.BESANCON-Bib. Electronique (250560099) / SudocSudocFranceF

ROM for nonlinear vibroacoustic problems with structural and acoustic nonlinearities

International audienceThis paper presents a reduced order method dedicated to nonlinear vibroacoustic problems. Both structural and acoustics behavior are nonlinear. The structural nonlinearity is due to large displacements while the acoustic nonlinearity is due to the high intensity level in the fluid. The Kuznetsov equation is used to formulate the nonlinear acoustic problem. The reduced order model is based on the Ritz bases of the uncoupled linear problem. Nonlinear behavior is considered as a perturbation of the linear model so that the resolution is compared to a reanalysis problem. The Combined Approximation method dedicated to reanalysis problems is used to enriche the Ritz reduced basis

Dynamics of stochastic and periodic structures in mid-frequency range

International audiencea hybridization of the Wave Finite Element Method (WFEM) with the Generalised Polynomial Chaos Expansion (GCE). The WFE is a spectral method dealing with wave propagation in periodic structure. This method proved its efficiency in different domains; structural vibration, non-destructive testing, etc. However, the WFE is limited to deterministic media. Knowing that uncertainties affect dynamic behavior in Mid- and High frequencies, the combination of WFE and GCE is used to predict the effect of uncertainties on the dynamic response of periodic media. The uses of the GCE is based on the iso-probabilistic transformations for usuel distributions to Gaussian one to use the Hermite-Chaos expansion.The presented approach is validated for two periodic waveguides connected through a junction with uncertain parameters. The obtained results are verified vs Monte Carlo simulations

Caracterisation dynamique et conception robuste d'interfaces de structures

Les structures mécaniques complexes résultent de l assemblage de plusieurs composants, possédant souvent des propriétés mécaniques différentes, reliés à leurs interfaces par différents types de jonctions. L hétérogénéité des comportements dynamiques de ces sous-structures et leurs sollicitations extérieures vont générer des efforts sur la structure principale et des accélérations importantes au niveau des équipements embarqués, affectant leur fonctionnement, leur fiabilité, leur sécurité. Il est alors nécessaire de les protéger en les isolant du reste de la structure.Ces travaux concernent la maîtrise des niveaux vibratoires et visent à fournir une méthode de caractérisation dynamique des interfaces entre différentes sous-structures. Celle-ci est ensuite intégrée dans une démarche visant à minimiser la puissance transmise entre des sous-structures sources et réceptrices.Une méthode de modes de flux de puissance a été développée, dont les valeurs et efforts propres fournissent, respectivement, des informations quantitatives et qualitatives sur les flux de puissance à l intérieur d une structure. Son application à l étude de la puissance transmise entre deux sous-structures permet d identifier les directions et les participations des principaux chemins de puissance transitant par les jonctions.Ces résultats ont été appliqués afin de proposer une méthodologie de conception robuste des interfaces de structures. Deux démarches d optimisation ont été comparées visant à minimiser la puissance transmise par rapport aux paramètres de raideurs des jonctions. L importance de considérer la robustesse de ces solutions a été soulignée par une approche complémentaire non-probabiliste.Complex mechanical structures are composed of an assembly of several components, often exhibiting different mechanical properties and joined at their interfaces by different junction types. The various dynamic behaviours of these substructures and the applied external loadings generate important efforts on the main structure, resulting in high acceleration responses of the on-board equipments, affecting their performance, reliability and security. It is therefore necessary to protect them from these harsh conditions by isolating them from the rest of the structure.These researches are related to structural vibration control and aim at proposing a new method to dynamically characterize interfaces between different substructures. This method is then integrated to a robust design approach to minimize the power transmitted between a source and a receiver substructure. A power flow mode method has been developed, which allows determining eigenvalues and eigenvectors respectively representing qualitative and quantitative information on the power flowing inside the structure. This has been further applied to study the power transmitted at the interface, making it possible to identify the direction associated to the dominant power flow pattern and to quantify their contribution.These results have been applied to propose a robust design approach of structural interfaces. Optimization procedures have been implemented and compared to minimize the power transmitted between with respect to the interface stiffness parameters. The importance of considering the robustness of these solutions has been underlined by performing a complementary analysis based on a non-probabilistic approach.BESANCON-Bib. Electronique (250560099) / SudocSudocFranceF

Récupération d'énergie vibratoire par voie électromagnétique sous excitation aléatoire

Ce travail porte sur l'étude d'un récupérateur d'énergie vibratoire électromagnétique soumis à une excitation aléatoire de type bruit-blanc. On utilise un modèle éprouvé pour extraire une règle de dimensionnement du récupérateur optimal soumis à une source vibratoire bruit-blanc et l'expression de la puissance maximale récupérable