2012/05/21 by Nathan Krapf, Nathan W. Krapf
Engineering · Materials Science · Mathematics · Physics and Astronomy · #Adhesion, Friction, and Surface Interactions #Anisotropy #Classical mechanics #Condensed matter physics #Geology #Geometry #Geotechnical engineering #Granular flow and fluidized beds #Granular material #Isotropy #Jamming #Material Dynamics and Properties #Materials science #Mathematics #Mechanics #Optics #Physics #Stress (linguistics) #Symmetry (geometry) #cond-mat.soft
paper · pdf · doi:10.1103/physreve.86.021302
published as Phys. Rev. E 86, 021302 (2012) · 21 pages, 21 figures
arxiv created 2012/05/21 · openalex publication_date 2012/08/01 · arxiv updated 2012/08/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We investigate how forces spread through frictionless granular packs at the jamming transition. Previous work has indicated that such packs are isostatic, and thus obey a null stress law which, independent of the packing history, causes rays of stress to propagate away from a point force at oblique angles. Prior verifications of the null stress law have used a sequential packing method which yields packs with anisotropic packing histories. We create packs without this anisotropy, and then later break the symmetry by adding a boundary. Our isotropic packs are very sensitive, and their responses to point forces diverge wildly, indicating that they cannot be described by any continuum stress model. We stabilize the packs by supplying an additional boundary, which makes the response much more regular. The response of the stabilized packs resembles what one would expect in a hyperstatic pack, despite the isostatic bulk. The expected stress rays characteristic of null stress behavior are not present. This suggests that isostatic packs do not need to obey a null stress condition. We argue that the rays may arise instead from more simple geometric considerations, such as preferred contact angles between beads.