VIBRATIONS, ACOUSTICS, MECHANICAL STRUCTURES AND SHAPES

The VAST-FM (Vibrations, Acoustics & Structures) topic develops methodologies intended to increase the reliability of predicting and controlling dynamic behaviours : vibrations, impacts and noise. The problems treated in the VAST-FM topic concern the dynamics, monitoring and diagnostics of systems, structures and materials, and dissipative behaviours (damping) in particular. Historic and recurrent works concern viscoelasticity, contact dynamics, and structured materials.

The team’s emerging contemporary work focuses on the integration of artificial intelligence tools in the field of dynamics, vibrations and signal and image processing.
The methods developed focus more particularly on real-time applications.

Damping in a few minutes …

 

TOPIC MANAGER

Jean-Luc DION (PU) - ISAE-Supméca
jean-luc.dion@isae-supmeca.fr

OUR ACTIVITIES FOCUS ON

lire la page dans un nouvel onglet

Viscoelasticity in a few minutes …

Polymer materials possess a considerable capacity to dissipate vibration energy. They are used to protect structures, equipment and passengers from vibration stresses, impacts and noise.

The challenges of characterising viscoelastic materials experimentally

To characterise these materials, their dynamic rigidity and loss angle are classically represented as a function of stress frequency. These experimental observations highlight the considerable evolution of these magnitudes as a function of frequency ranges (figure 2).

Figure 2 : Representations of frequency

The experimental characterisation of these properties, called Dynamic Mechanical Analysis is difficult because the frequency range to be covered by the test resources is often very large and hard to access with only one experimental device. Furthermore, the mechanical characteristics of viscoelastic materials strongly depends on temperature. The first solution is to make use of the principle of time-temperature equivalence. This method is based on vibration tests in a relatively narrow frequency bandwidth carried out at different temperatures. Time-temperature equivalence permits building the dynamic behaviour of the material over a large frequency bandwidth for a given temperature.

This method presents several measurement biases the chief of which stems from the time-temperature equivalence hypothesis which is not always verified depending on the material studied. In many cases of materials stemming from industry such as multilayer materials, loaded polymers, functionalised materials and structural adhesives, the time-temperature equivalence is not valid. The characterisation of the material’s dynamic properties must therefore be done at the temperature and frequency bandwidth corresponding to its real utilisation conditions.

Over the last few decades, the VAST team has developed innovative and efficient viscoanalysers capable of directly characterising the dynamic mechanical properties of these materials in different stress configurations (traction-compression, shearing, combined static and dynamic loading, etc.). These new experimental technologies (figure 3) now permit the direct characterisation of viscoelastic materials (without time-temperature equivalence and without passing via modes specific to the experimental set up) up to 10kHz.

Figure 3 : 3 viscoanalyzers developed at Supméca

Performing these tests under different pre-loads and different stress amplitudes permits the detailed characterisation of the nonlinear viscoelasticity of the material studied.

The quality of the experimental data obtained from these tests is an essential parameter when predicting the dynamic behaviours of components and structures in which viscoelastic materials are used.

The challenges of modelling viscoelastic materials

The experimental data on the dynamic behaviours of viscoelastic materials are mainly obtained to feed predictive models of components, structures and systems.

The viscoelastic mechanical behaviours can be mainly described by two families of model : those based on non-integer derivatives and those based on elementary rheological components such as the generalised Maxwell model.

The first limitation in modelling stems from the identification of the parameters used in these models. This point has been dealt with in several publications by the VAST team [1 – 3] and exploited by several industrial partners (Hutchinson, BOSCH Braking Systems, AER, ADERIS).

The second limitation dealt with by the VAST team concerns the integration of these models in off-the-shelf structure calculation codes [4,5].

Viscoelasticity has been a highly active area of research for decades and has now found new areas of investigation with functionalised materials, metamaterials, additive manufacturing, bio-sourced and environmentally friendly materials and those that comply with sustainable development.

[1] J.-L. Dion and S. Vialard, “Identification or rubber shock absorber mounts,” Mécanique industrielle et matériaux, vol. 50, no. 5, pp. 232–237, 1997.

[2] F. Renaud, J.-L. Dion, G. Chevallier, I. Tawfiq, and R. Lemaire, “A new identification method of viscoelastic behavior : Application to the generalized maxwell model,” Mechanical Systems and Signal Processing, vol. 25, no. 3, pp. 991 – 1010, 2011.

[3] H. Jrad, J. L. Dion, F. Renaud, I. Tawfiq, and M. Haddar, “Experimental characterization, modeling and parametric identification of the non linear dynamic behavior of viscoelastic components,” European Journal of Mechanics – A/Solids, vol. 42, no. 0, pp. 176 – 187, 2013.

[4] S. Thouviot, G. Chevallier, F. Renaud, J.-L. Dion, and R. Lemaire, “Prise en compte des comportements viscoélastiques dans la simulation dynamique des systèmes de freinage,” Mechanics & Industry, vol. 10, no. 05, pp. 385–396, 2009.

[5] H. Festjens, G. Chevallier, F. Renaud, J.-L. Dion, and R. Lemaire, “Effectiveness of multilayer viscoelastic insulators to prevent occurrences of brake squeal : A numerical study,” Applied Acoustics, vol. 73, no. 11, pp. 1121 – 1128, 2012.

lire la page dans un nouvel onglet

Damping in granular environments in a few minutes ...

We focus on the propagation and attenuation of waves and vibrations in granular media, like sand, by conducting experiments on model systems in the laboratory. The particularities of granular media are (i) that they interact according to very nonlinear Hertz potential when they are dry, and more generally (ii) they involve singular mechanisms associated with contacts between geometrically heterogeneous particles : this is the case of wet granular media, particularly colloidal suspensions, when an interstitial fluid is confined between the particles and causes a complex elasto-hydrodynamic interaction.

Propagation d’ondes dans un cristal phononique

The propagation of waves in a phononic crystal creates an alignment of centimetric particles interacting via Hertz’s nonlinear potential ; an instrumented particle reveals the inaccessible wavelengths of such networks (PRL 2005PRL 2010).

Another advantage of granular media is that they (iii) present crystalline symmetries when the particles are the same or on the contrary (iv) in disorder when the grains are polydispersed. Lastly, they are known (v) to be highly dissipative, in particular by activating powerful frictional effects.

Propagation d’ondes dans un milieu granulaire mouillé

Wave propagation in a granular material wetted by the addition of a small quantity of viscous interstitial fluid ; measuring the relation of dispersion shows that the fluid initiates an elasto-hydrodynamic interaction resulting in the stiffening of contacts, increased propagation speed and greater dissipation (Thèse 2016 Kamil Chrzaszcz)

Observation directe de la propagation d’une impulsion dans une suspension colloïdale

Direct observation of the propagation of a pulse in a colloidal suspension to show the role played by the elasticity of particles, the viscosity of the fluid and the topological disorder in the attenuation length and transport properties (PNAS 2017).

Research carried out in the laboratory, essentially experimental, involves several scales (centimetric, millimetric and micrometric), from contact dynamics (dry and wet), to modelled structures (phononic crystals composed of periodic alignments of spheres), and disordered stacks of vibrated grains (granular dissipator).

Mesure du facteur de perte et de la masse effective d’un dissipateur granulaire

Measure of the loss factor and the effective mass of a granular dissipator ; the loss factor of this system is proportional to the mass of vibrated grains, whose apparent mass decreases until disappearing with the amplitude of acceleration (Thèse 2016 Marwa Masmoudi, Gran. Matt. 2016).

Phase transitions in vibrated granular media. Defense of Rene Zuniga, 25/02/2021

lire la page dans un nouvel onglet

Acoustic absorption and attenuation represent a major challenge for many applications in construction, transport and ventilation systems. These practical aspects are linked to acoustic propagation in thermo-viscous fluids and taking into account sub-wavelength structure.

These mechanisms are the basis of models of porous and materials, poroelastic materials and metamaterials in which the competition between resonances and dissipation is crucial for their functioning (ANR METAUDIBLE 2013-2017).

Atténuation dans un guide d’onde traité par un métaporeux. Onde guidée, métamatériaux, homogénéisation.

Attenuation in a waveguide treated by a metaporous material. Guided wave, metamaterials, homogenisation.

Accounting for losses remains a challenge for simulation and allows exploring unusual wave phenomena such as exceptional points (Collaboration UTC).

The team develops simulation methods, such as the EasterEig, project,
new materials and the associated experimental resources.

 

Metamaterials for conduit attenuation (collaboration LAUM Xiong, Aurégan, Bi https://dx.doi.org/10.1121/1.5007851)

Microstructure of a polymer foam (SEM SUPMECA)

Surface de Riemann illustrant un point exceptionnel (fusion de 2 valeurs propres)

Riemann surface illustrating an exceptional point (fusion of 2 eigenvalues)

lire la page dans un nouvel onglet

During the design phase of a structures, predicting their dynamic behaviour is often degraded by errors due to the poor evaluation of their global damping. The level of the vibration is heavily dependent on the damping caused by the assemblies of substructures with each other. This damping is consecutive to a loss of energy by friction due to partial sliding in the linking interfaces. The purpose of these works is to focus on this energy dissipated by friction occurring during the vibrations of the structure and influencing its dynamic behaviour.

photo illustrant un essai d'Amortissement et dissipation d'énergie dans les assemblages

The works performed are aimed at :

  • quantifying this damping experimentally,
  • evaluating this damping at different scales (microgeometric contact, link, structure) numerically.

Moreover, recent works are aimed at designing and prototyping damping link technologies for metal assemblies. The justification of these works is based on the fact that modern structures must combine reliability, lifetime, comfort, lightness, low-cost, rapidity and reduced energy consumption. Taken separately, although of different natures, these parameters are all improved when damping in the structure is increased. The reduction of vibrations always results from a compromise between these different parameters and the addition of damping cannot improve them all at once. These works are aimed at maximising the contribution of damping in mechanical links and more generally to improving the performance of structures.

Photo illustrant un essai Amortissement et dissipation d’énergie dans les assemblages

The research carried out is supported by institutes and industrial companies in the framework of research programmes (R&T CNES, FUI (MAIAS, CLIMA), IRT SystemX, EDF, ASTECH, JPB SYSTEM, AIRBUS, SOPEMEA, AVNIR, SDTOOLS, FCBA.

lire la page dans un nouvel onglet

Mesure de champs vibratoires par cameras rapides

Vibration analysis of mechanical systems and structures is vital to determine their behaviour in operating conditions and following exceptional events. Therefore, the experimental study of the vibrations of a system (mechanical, aeronautical, civil) is henceforth an essential step in the design and monitoring process. To this end, in addition to traditional measurement tools such as piezoelectric accelerometers, laser movement sensors and laser vibrometers, high speed cameras are a solution for the future, capable of filming large scenes without contact at very high speeds, in the region of thousands of images a second.

Measurements by high-speed cameras permit defining the vibratory fields of a structure, in both transient and stationary regimes, while the use of several cameras surrounding the structure allows measuring its behaviour in 3D, and to detect the oscillations of elements difficult to reach with classical measurement instruments. This is the case for example of the edges of a contact interface in a link, or the free surface of a fluid in a rigid container in movement.

Our studies therefore focus on the utilisation of this new technology, with particular attention given to the following points :

  • image processing (binarisation, code optimisation, reduction of calculation time) ;
  • detection of features (points, edges, surfaces, fluids) ;
  • target tracking ;
  • data filtering and assimilation ;
  • operational modal analysis by multi-viewpoint 3D ;
  • reconstruction of the behaviour of a 3D structure using models and measures ;
  • real-time vibration analysis.

More specifically, features can be detected using the image processing algorithms developed, and their movement tracked throughout dynamic tests. Signal filtering and data assimilation techniques provide the information required to perform modal experimental analysis and identify the dynamic properties of the system studied. Our research also aims at developing methods of analysing vibration behaviour in real-time while relying on the synergy between experimental measures and numerical models.

Trois type d'images de mesure de champs vibratoires par cameras rapides

Experimental measurement campaigns are performed in the VAST team’s test laboratory, and in the framework of research projects (FUI CLIMA, EUGENE) and collaborations with academic and industrial establishments (University of Liege, SOPEMEA).

MEASURING FIELDS BY CAMERA IN A FEW MINUTES...

lire la page dans un nouvel onglet

In parallel to the development of methods to measure fields applied to structural dynamics, the VAST team carries out research on data assimilation methods aimed at feeding in real-time the link between a dynamic system and its numerical twin.

The methods developed are based on Bayesian stochastic approaches (Kalman filters) and built with systems of states obtained from structural and solid dynamics.

The data assimilation studies are supplied by very different sensor technologies including high-speed cameras, accelerometers, force sensors, etc. and aim at enhancing the quality of models and capitalising the results of simulations and measures.

Aile d'avion recouverte de capteurs

These techniques are developed in different areas of application (structural dynamics, multibody dynamics, analysis of the dynamic failure modes of a production line) with different industrial partners in aeronautics, automobiles and cosmetics (AIRBUS, SOPEMEA PSA, PUIG, PKB, VISIOLASER)

The digital twin in few minutes...

lire la page dans un nouvel onglet

Analysing the dynamic behaviours of structures, whether in the framework of studying their linear vibrations or not, coupled multiphysics and vibroacoustics problems, problems of transient responses and high-speed dynamics, lead to building models that require huge numerical resources. Such models are often difficult to implement or reveal themselves to be poorly adapted when using such analyses in iterative optimisation procedures applied to exploring the preliminary design of a large number of configurations of the same system and for varied and/or extended ranges of frequencies. This is also the case when designing real-time diagnostics systems and implementing them in embedded mechatronic systems.

Using scale models is one of the methods that the VAST topic has developed and used for twenty years to deal with these problems. These models provide it with efficient and robust simulation tools perfectly adapted to the type of simulation considered and the numerical resources available. The techniques of reducing the models used classically in structural dynamics, based on the utilisation of modal bases and on experimental modal analysis, are extended to nonlinear problems and Multiphysics problems. Current efforts consist in completing these approaches by meshless type models. Continuous models of structural elements made of orthotropic materials are being developed in the framework of the Dynamic Stiffness Method and utilised for the design of smart structures.

Regular industrial partnerships lead to the exploitation of these approaches to develop operational tools that respond precisely to the demands of designers. (Renault, Thales, etc.).

 

Modèle continu de type Meshless

Figure 1: Meshless type continuous model

The team’s activities are focused on transport technologies (aeronautics, aerospace, automobiles, railways, and marine transport), civil structures subject to dynamic stresses and energy production systems. These activities are carried out in partnership with industrial groups (AIRBUS, ARIANE Group, SAFRAN, RENAULT, PSA, PTC (FAYAT), JPB SYSTEME, KEYPROD, NEXTER, ALSTOM, etc.) and partner laboratories (ONERA, LAMCOS INSA Lyon, ROBERVAL – UTC, Institut NAVIER – ENPC, etc.).

Collaborations

The team’s activities are centred on transport technologies (aeronautics, space, automotive, railway and naval), civil structures subjected to dynamic loads and energy production systems. These activities are conducted in partnership with industrialists (AIRBUS, ARIANE Group, SAFRAN, RENAULT, PSA, PTC (FAYAT group), JPB SYSTEME, KEYPROD, NEXTER, ALSTOM...) and partner laboratories (ONERA, LAMCOS INSA Lyon, ROBERVAL - UTC, Institut NAVIER - ENPC...)

Academic collaborations are maintained through institutional projects (ANR, Europe, Region) with :

ONERA, LAMCOS INSA Lyon, ROBERVAL - UTC, FCBA, LAUM-Univ. LE MANS, Institut NAVIER - ENPC,...

Internationally :

Sandia, CAlTech, Politechnico Di Torino, Univ. Di Napoli, Imperial College of London, ...

 

The VAST-FM team is involved in the European ENERMAN project (2021-2025) on the energy optimisation of large industrial sites using intelligent sensor networks and Artificial Intelligence tools. Two theses are supervised in the team : on the one hand on intelligent sensor networks observing dynamic, vibratory, thermal and electrical behaviour and on the other hand on Machine Learning tools using data assimilation methods and dynamic models.

TOPIC news

Outreach

visiting/associate researchers, external post-docs, international student exchange

TEAM COMPOSITION

Research engineer

Tél.: +33 1 49 45 25 47
Mél: mireille.moinet@isae-supmeca.fr

Location ISAE-SUPMECA

Full professor

Tél.: +33 1 49 45 29 00
Mél: alain.riviere@isae-supmeca.fr

Location ISAE-SUPMECA

Assistant professor

Mél: philippe.serre@isae-supmeca.fr

Location ISAE-SUPMECA

Assistant professor

Mél: reda.sellakh@isae-supmeca.fr

Location ISAE-SUPMECA

Full professor

Tél.: +33 1 49 45 29 63
Mél: jean-baptiste.casimir@isae-supmeca.fr

Location ISAE-SUPMECA

Dynamique des structures,
Méthodes « Meshless »
Viscoélasticité

Full professor

Tél.: +33 1 49 45 29 12
Mél: jean-luc.dion@isae-supmeca.fr

Location ISAE-SUPMECA

Vibrations non linéaires
Traitement du signal
Dynamique Multicorps

Page perso. Researchgate

Assistant professor

Tél.: +33 1 49 45 29 00
Mél: stephane.job@isae-supmeca.fr

Location ISAE-SUPMECA

Docteur en acoustique – Expérimentateur
Ondes et vibrations non-linéaires, Milieux granulaires, Réseaux phononiques,
Métamatériaux

Assistant professor

Mél: stefania.lofeudo@isae-supmeca.fr

Location ISAE-SUPMECA

Contôle passif des vibrations
Vibrations non linéaires
Mesure de champs par camera rapide

ResearchGate

Assistant professor

Tél.: +33 1 49 45 29 00
Mél: martin.ghienne@isae-supmeca.fr

Location ISAE-SUPMECA

Dynamique stochastique des structures
Mesure de champs par camera rapide

Assistant professor

Tél.: +33 1 49 45 28 02
Mél: benoit.nennig@isae-supmeca.fr

Location ISAE-SUPMECA

Acoustique
Matériaux absorbants
Méthode numérique
Ondes guidées

https://cv.archives-ouvertes.fr/ben...

Associate Professor

Mél: nicolas.peyret@isae-supmeca.fr

Location ISAE-SUPMECA

Amortissement des structures
Calcul non linéaire des structures
Conception

Associate Professor

Mél: franck.renaud@isae-supmeca.fr

Location ISAE-SUPMECA

Dynamique des structures
Viscoélasticité
Dynamique Multicorps

Lecturer

Tél.: +33 1 49 45 29 00
Mél: alain.stricher@isae-supmeca.fr

Location ISAE-SUPMECA

Tolérancement des structures assemblées

Research project proposals