1 / 15

Forces and Fluctuations in Dense Granular Materials

Forces and Fluctuations in Dense Granular Materials. R.P. Behringer, Dept. of Physics, Duke University. Discussant: C.S. O’Hern, SEAS, Dept. of Physics, Yale University. Quantitative characterization of force chains!. Where it all began…. Temporal fluctuations. Duke University. 1994.

joelle-daugherty
Download Presentation

Forces and Fluctuations in Dense Granular Materials

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Forces and Fluctuations in Dense Granular Materials R.P. Behringer, Dept. of Physics, Duke University Discussant: C.S. O’Hern, SEAS, Dept. of Physics, Yale University Quantitative characterization of force chains!

  2. Where it all began… Temporal fluctuations Duke University 1994

  3. Spatial fluctuations

  4. Anisotropy • How does anisotropy affect • the ‘isotropic’ jamming picture? • New critical points, related critical • points, controlled by point J,…? • What is the coupling between • friction and anisotropy, e.g. more • anisotropic fabrics? Isotropic compression Shear fabric

  5. What are the differences between isotropic and anisotropic jammed systems?

  6. Difference I Isotropic compression Shear Different contact networks or fabrics

  7. Difference II Isotropic Compression Shear • Broad normal force distributions Snoeier et al. PRL 92, 054302 (2004) Tighe et al. Phys. Rev. E, 72, 031306 (2005)

  8. Difference III Shear Compression Both directions equivalent Chain direction Direction  normal To chains • Local ‘pressure’ correlations are anisotropic longer ranged

  9. Difference III Isotropic compression Pure shear Simulations of Jammed Packings Chakraborty, Henkes, Lois, O’Hern, Majmudar, Behringer, 2008

  10. Difference IV • Distribution of jamming onsets P(JA) changes, e.g. shear dilation

  11. Two ways to measure distribution P(JA) V Quasistatic shear at constant =0.85 1’ 3’ 5’ 3’ 1 3 5 Dynamics from one inherent structure to another 1’ 3’ 5’ Associated jammed states V Quasistatic shear at constant ‘pressure = 0’ Dynamics from one jammed state to another 1 4  7

  12. Quasistatic shear at constant =0.85 shear distribution of jamming onsets N~100 no shear shear JA • Distribution of jamming onsets shifts, i.e. shear dilation

  13. Shear at constant ‘Pressure=0’ • Number of jamming onsets depends on shear because fabrics are different • Does packing fraction even matter at all? Or is the family or fabric the more important variable even • if 0? V=0 strain JA  family/fabric

  14. Point J is not really a single point? RCP-RLP ? unjammed jammed 1/ Points JAF Point JA Point J • For frictionless isotropic jammed packings, there is an infinite number of J-points, but they all have same J when N  and similar fabrics • For frictionless anisotropic jammed packings, there is a different infinite set of JA-points with possibly different JA that depend on the fabric. What happens when N  ? • For frictional jammed packings, there is an infinite set of jammed • packings over a finite rangeRLP to RCP when N.

  15. Questions 1. How do we understand anisotropy? 2. Do anisotropic ‘critical’ points exist that ‘control’ response of anisotropic systems to deformation, and how do they relate to ‘isotropic’ jamming framework? 3. What is the density of states as a function of the fabric? Gao, Lois, O’Hern, 2008.

More Related