Final report
Dates and location
11 July — 13 July 2016, France
Chairperson
Guillaume James
Co-chairperson
Chiara Daraio, Alexander F. Vakakis
Conference fees
- Accompanying person at the conference dinner: 50.00 €
- Late Registration Fee: 340.00 €
- Regular Registration Fee: 240.00 €
What other funding was obtained?
-
What were the participants offered?
-
Applicants (members)
- Simon Charlemagne
- Frédéric Dubois
- Oleg Gendelman
- Guillaume James
- Daniil Kolesov
- Michael Leamy
- Stefan Luding
- Leonid Manevitch
- Francesco Romeo
- Alireza Ture Savadkoohi
- Alexander Vakakis
- Nathalie Vriend
Applicants (non members)
- Florian Allein
- Nicholas Boechler
- Nestor Bohorquez
- Maurice Bremond
- Bernard Brogliato
- Martina Chirilus-Bruckner
- Christopher Chong
- Karen Daniels
- Chiara Daraio
- Gilles Daviet
- Lucio De Abreu Correa
- Zoran Dimitrijevic
- Vladimir Erofeev
- André Foehr
- Sebastian Huber
- Stephane Junca
- Victor Kislovsky
- Dennis Kochmann
- Margarita Kovaleva
- Stefano Lepri
- Bruno Lombard
- Vanessa Magnanimo
- Mehul Makwana
- Alexey Malkhanov
- Aurelien Merkel
- Jose Morales
- Shin-Ichiro Nagahiro
- Corey Ohern
- Franck Pérignon
- Arkady Pikovsky
- Laurent Ponson
- Stephane Redon
- Vincent Richefeu
- Vassilios Rothos
- Massimo Ruzzene
- Kuniyasu Saitoh
- Krishna Kant Singh
- Yuli Starosvetsky
- Brian Tighe
- Zofia Trstanova
- Anna Vainchtein
- Alexandre Vieira
- Vincenzo Vitelli
- Jinkyu Yang
Scientific report
The Colloquium focused on the nonlinear dynamics of granular media (disordered packings or ordered granular metamaterials) and mechanical metamaterials from a broad perspective : experiments, physical modeling, numerical and analytical methods, applications, connection with industrial problems (modeling of ballasted railway tracks, silo honking, vibration absorbers in vehicles). The conference brought together 54 participants from 11 countries, mixing researchers from the applied mathematics, engineering, nonlinear physics and mechanics communities. The program comprised 38 talks and 11 poster presentations, leading to many stimulating discussions and exchange of ideas mong participants.
For the metamaterials community, it was extremely useful to learn about continuum models and numerical methods developed in the context of disordered granular media or more general systems of interacting particles (micro-macro transition methods, models including nonlocal interactions, nonsmoothness or stochasticity, adaptively restrained particle simulations, SAMSON and SICONOS softwares), and to be aware of up-to-date experimental approaches (network-based characterization of force chains). In addition, some nonlinear phenomena which have been discussed
in the framework of disordered granular materials may lead to future design principle in the metamaterials setting. For example, force chains forming in granular assemblies may be used to induce nonintuitive macroscopic mechanical properties, such as an enhanced stiffness obtained by introducing an optimal proportion of softer particles.
Conversely, granular metamaterials provide a simplified framework to investigate grain- or meso-scale processes in disordered granular media, with the goal of understanding larger-scale phenomena. In this way, some topics which have been discussed in the context of ordered metamaterials and nonlinear mechanical networks could provide new interesting theoretical approaches to get deeper insight into the physics of granular matter. This is the case for example with the analysis of stress wave propagation along branched granular chains which mimick the force chains
forming in the bulk of a granular medium. Another example concerns the nonlinear energy transfer between vibrational modes, which is widely studied in the context of periodic lattice dynamical systems, in particular those modeling ordered granular media. Theoretical and numerical methods developed in this field could find
applications to analyze vibrations in disordered granular media near the onset of jamming.
The interaction between groups working on mechanical metamaterials on the experimental side and nonlinear lattices on the theoretical side was also extremely fruitful. This connection arises naturally because different types of nonlinear lattices such as the Fermi-Pasta-Ulam and discrete Klein-Gordon models or mass-in-mass chains, can be realized through various types of mechanical metamaterials reviewed during the conference : granular chains, woodpile phononic crystals, networks of snapping structures, magnets or Helmholtz resonators. As a consequence, different nonlinear wave phenomena investigated theoretically can be realized experimentally (solitary waves, breathers, phase transition waves, wave redirection,…). In this context, the Colloquium provided a forum to review useful theoretical concepts (e.g. amplitude equations, effective particles and limiting phase trajectories, techniques
from nonsmooth systems), suggest design principles inspired by theory (e.g. to implement nonlinear energy diffusion) and unveil new interesting theoretical problems. As described in several talks, the high tunability of certain metamaterials (such as 3D-printed mechanical structures, Helmholtz resonators with variable characteristics, branched granular networks) and the possibility to introduce timemodulated mechanical properties (e.g. using piezo-electric patches) can lead to new dynamical effects and arise interesting theoretical questions.
Challenging new directions reviewed in the Colloquium include the analysis of adhesion effects in microscale or magnetic granular crystals, nonlinear wave phenomena involving rotations of grains, two and three-dimensional wave
propagation in granular crystals (conical diffraction regimes, wave instabilities), interaction of continuous elastic media with nonlinear oscillators (such as mechanical oscillators, granular chains, cracks), breaking of time-reversal symmetry. Another important concept rewiewed during the conference is the notion of topologically
protected modes, preserved under smooth deformations or imperfections of a metamaterial : edge modes in 1D and 2D linear systems, nonlinear extensions (domain wall motion in 1D networks of bars connected by joints).
Applications of the above concepts discussed during the conference concerned shock mitigation (e.g. using turbulence-like attenuation of stress waves), vibration isolation (e.g. by concentrating energy into edge modes), wave guiding, nonlinear diodes, mechanical logic gates, detection of cracks.
The organization committee has received highly positive feedback from many participants concerning the Colloquium. We think that this conference will certainly foster new collaborations between researchers with different areas of expertise and generate notable contributions to the field. We are grateful to all contributors for their beautiful talks and active participation, and acknowledge EUROMECH and INRIA for their support which was essential to organize this conference.
Number of participants from each country
| Country | Participants |
|---|---|
| France | 21 |
| United States | 10 |
| Netherlands | 5 |
| Russia | 5 |
| Switzerland | 4 |
| Israel | 3 |
| Italy | 2 |
| Japan | 2 |
| French Guiana | 1 |
| Germany | 1 |
| Greece | 1 |
| United Kingdom | 1 |
| Total | 56 |