Displacement fields in sheared particle packings often display vortex-like structures that reveal essential features about the mechanical state of the collection of particles. There are several metrics to quantify these flow field features, yet extracting such quantitative metrics from flow field or particle tracking data involves
making numerous choices on the time and length scales over which to average. Here we employ a much used experimental data set on sheared disk packings to explore how such arbitrary data mining choices affect the obtained results. We focus on calculating the strain dependent vorticity, as this metric is a differential method hence potentially sensitive to the way it is computed. We find that the total surface area with an absolute vorticity above a certain threshold approaches a plateau value as shear progresses. This plateau value exhibits a non-monotonic dependence on packing fraction. We also show which range of choices yields results that can
support an analysis method independent, physical interpretation of the flow field data.

Strain dependent vorticity in sheared granular media

Granular systems are not always homogeneous and can be composed of grains with very different mechanical properties. To improve our understanding of the behavior of real granular systems, in this experimental study, we compress 2D bidisperse \md{systems} made of both soft and rigid grains. By means of a recently developed experimental set-up, \md{from the measurement of the displacement field we can} follow all the mechanical observables of this granular medium from the inside of each particle up to the whole system scale. We \md{are able to} detect the jamming transition from these observables and study their evolution deep in the jammed state for packing fractions as high as $0.915$. We show the uniqueness of the behavior of such a system, \md{in which way} it is similar to purely soft or rigid systems and how it is different from them. This study constitutes the first step toward a better understanding of the mechanical behavior of granular materials that are polydisperse in terms of grain rheology.

Highly strained mixtures of bidimensional soft and rigid grains: an experimental approach from the local scale

We use bi-dimensional non-smooth contact dynamics simulations to analyze the isotropic compaction of mixtures composed of rigid and deformable incompressible particles. Deformable particles are modeled using the finite-element method and following a hyper-elastic neo-Hookean constitutive law. The evolution of the packing fraction, bulk modulus, and particle connectivity, beyond the jamming point, are characterized as a function of the applied stresses for a different proportion of rigid/soft particles and two values of friction coefficient. Based on the granular stress tensor, a micro-mechanical expression for the evolution of the packing fraction and the bulk modulus are proposed. This expression is based on the evolution of the particle connectivity together with the bulk behavior of a single representative deformable particle. A constitutive compaction equation is then introduced, set by well-defined physical quantities, given a direct prediction of the maximum packing fraction $\phi_{max}$ as a function of the proportion of rigid/soft particles.

A micro-mechanical compaction model for granular mix of soft and rigid particles

Poster Session

poster

[EPJ Web of Conferences, Volume 249 (2021)](https://www.epj-conferences.org/articles/epjconf/abs/2021/03/contents/contents.html)

Follow us on [Twitter](https://twitter.com/g2021_p)

**Meet the Organizers**

<center>
<figure class="video_container">
	  <iframe src="https://screencast-o-matic.com/watch/cr130qV10B3?v=6&ff=1&title=0&controls=1" width=826 height=526  frameborder="0" allowfullscreen="true"> </iframe>
</figure>
	</center>


Welcome to the 2021 Powders and Grains conference. Please review the event's **Code of Conduct** [here](https://drive.google.com/file/d/1P_bOrjI2jSE55twRPVzWl5VkfARR-qBL/view?usp=sharing). 


**Powders & Grains 2021 Walkthrough Screencast**

This video will demonstrate how to navigate the conference and virtual platform -- and network with other attendees and speakers.


<center>
<figure class="video_container">
	  <iframe src="https://screencast-o-matic.com/watch/cr1vnKV1pgn?v=6&ff=1&title=0&controls=1" width=826 height=526  frameborder="0" allowfullscreen="true"> </iframe>
</figure>
	</center>

To register for the event, please follow the link below. 

Powders & Grains 2021

Powders & Grains 2021 will be held in Buenos Aires (Argentina, VIRTUAL) July 5, 13, 21, 29 and Aug 6, 2021. The aim of the conference is to give an up-to-date picture of the broad research field of granular media, powders and grains. Contributions from experts around the world will focus on research topics that cover a wide range of open problems in the field.

**Session Chairs:**
<br>
<br>Alejandra Aguirre and Luis Pugnaloni

Jonathan Barés

3

14

SHORT BIO

Presentations

Strain dependent vorticity in sheared granular media

Highly strained mixtures of bidimensional soft and rigid grains: an experimental approach from the local scale

A micro-mechanical compaction model for granular mix of soft and rigid particles

Stay up to date with the latest Underline news!

PRESENTATIONS

CONFERENCES

COMPANY

RESOURCES