报告摘要：

Granular media are fascinating, complex materials that  display gas-, liquid-, and solidlike behavior depending on the boundary and driving conditions. Frictional forces are crucial for determining the structural and mechanical  properties of granular media in the solidlike state. To predict the functional form of the  contact number with friction, we develop a theoretical description for mechanically stable frictional packings in terms of the  difference between the total number of contacts required for isostatic packings of frictionless disks and the number of contacts in frictional packings, m= Nc,0 − Nc. The saddle order m represents the number of unconstrained degrees of freedom that a static packing would possess if friction were removed. Using a novel numerical method that allows us to enumerate disk packings for each m, we show that the probability to obtain a packing with saddle order m at a given static friction coefficient can be expressed as a power series. Using this form, we quantitatively describe the dependence of the average contact number on the friction coefficient for static disk packings obtained from direct simulations of the Cundall-Strack model.

报告人简介：

Corey S. O'Hern is an Associate Professor with Tenure in the Departments of Mechanical Engineering & Materials Science, Applied Physics, and Physics and Graduate Program in Computational Biology & Bioinformatics at Yale. Before joining the faculty at Yale, he was a postdoctoral fellow working with Prof. Andrea Liu (UPenn, Physics) who was then at UCLA and Prof. Sidney Nagel (UChicago, Physics) on computational studies of jamming transitions in frictionless granular materials and glass transitions in model glass-forming liquids. Corey recieved his Ph.D. in Physics from the University of Pennsylvania in 1999; his dissertation focused on developing elasticity theories for liquid crystalline systems with biological importance such as DNA-cationic lipid complexes. See his Ph.D. thesis. Corey was an undergraduate at Duke University and graduated in 1994 with a B.S. in Physics. He likes to point out that while at Duke, he performed experimental research on granular materials in Bob Behringer's Lab and to his knowlege did not break anything!