Award Abstract #0137119
Force Propagation and Friction in Granular Materials

NSF Org:	DMR Division of Materials Research
Initial Amendment Date:	April 3, 2002
Latest Amendment Date:	August 12, 2005
Award Number:	0137119
Award Instrument:	Continuing grant
Program Manager:	Wendy W. Fuller-Mora DMR Division of Materials Research MPS Directorate for Mathematical & Physical Sciences
Start Date:	March 15, 2002
Expires:	February 28, 2006 (Estimated)
Awarded Amount to Date:	$389411
Investigator(s):	Robert Behringer bob@phy.duke.edu (Principal Investigator) Joshua E. S. Socolar (Co-Principal Investigator)
Sponsor:	Duke University 2200 W. Main St, Suite 710 Durham, NC 27705 919/684-3030
NSF Program(s):	CONDENSED MATTER PHYSICS
Field Application(s):	0106000 Materials Research
Program Reference Code(s):	AMPP, 9161
Program Element Code(s):	1710

ABSTRACT

This is a combined experiment and theory/modeling condensed matter physics project. The objective is to understand force propagation in granular materials. Granular materials have been the focus of an intensive and growing body of research that also extends to a broader class of materials, such as glasses, colloids, foams and others that exhibit jamming (frozen structures). New techniques are being invented to deal with these materials, which cannot be described in the context of conventional statistical mechanics. Thus, concepts arising from this project have potential to impact a broad range of materials handling problems, which arise with food grains, coal and ores and pharmaceutical powders and other granular materials. In these materials, forces are carried by an inhomogeneous network of so-called stress chains, which form and reform, leading to strong spatio-temporal stress fluctuations. This project will address at least four different systems that exhibit force propagation and fluctuations. Theory/modeling aspects of this work focus on micro/mesoscopic models of stress propagation, while Molecular Dynamics techniques are brought to bear on force fluctuations. This project involves undergraduates, graduate students and post-docs in an integrated program of training and development. More senior students and post-docs train undergrads through appropriate research projects. Graduate students and post-docs receive training in advanced research techniques that prepare them for either academic or industrial careers.

This project will focus on the behavior of granular materials, which include a broad spectrum of technologically and industrially relevant products ranging from food grains to coal and ores to pharmaceutical powders. The value added to the US economy in the handling of these materials is estimated to be as much as a trillion dollars a year. However, our understanding of the basic physics of these materials is incomplete, and this translates into a corresponding loss of productivity in dealing with these materials. This project focuses on such basic physics issues as how forces are carried in these materials and how the materials behave when they are subject to applied forces, such as those that might be encountered in handling devices. Important insights sought with this project should include better predictability of materials properties, as well as insight into the limits of this predictability. This project involves undergraduates, graduate students and post-docs in an integrated program of training and development. Grad students and post-docs will help undergrads through appropriate research projects. Undergraduates learn key research techniques, and also training in instrumentation development. Graduate students and post-docs receive training in advanced research techniques that will prepare them for either academic or industrial careers.

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