Granular Crystallization Driven by Dynamic Jamming Front

Mono-dispersed particle systems under moderate vibration or continuous shearing are prone to form crystallized packing structures. Our grain scale simulations also find a collection of initially unjammed mono-dispersed particles would jammed into ordered packing structures by uniaxial compression via a rake. The crystallization degree, indicated by the local order of individual particles and the number of ordered particles, is found to be strongly influenced by the inter-particle friction. For the smooth particles, crystallization ensues the propagating jamming front regardless of the disorder degree of initial particle arrangement. A trivial friction (m = 0.01) suffices to markedly reduce the crystallization degree from above 90% to 68% thanks to the emergence of shear bands. An increased friction (m = 0.3) induces profuse shear bands, contributing to a significant reduction of crystallization degree (below 40%) which is also correlated with the initial disorder degree. As expected, the order-to-disorder transition of jammed structure induced by increasing particle friction dictates the jammed packing fraction and consequently the dynamic of jamming front. We also reveal mechanisms underlying the dynamic crystallization and its degeneration due to the elevated particle friction.