Probability analysis of contact forces in quasi-solid-liquid phase transition of granular shear flow

Abstract

The quasi-solid-liquid phase transition exists widely in different fields, and attracts more attention due to its instinctive mechanism. The structure of force chains is an important factor to describe the phase transition properties. In this study, the discrete element model (DEM) is adopted to simulate a simple granular shear flow with period boundary condition on micro scale. The quasi-solid-liquid phase transition is obtained under various volume fractions and shear rates. Based on the DEM results, the probability distribution functions of the inter-particle contact force are obtained in different shear flow phases. The normal, tangential and total contact forces have the same distributions. The distribution can be fitted as the exponential function for the liquid-like phase, and as the Weibull function for the solid-like phase. To describe the progressive evolution of the force distribution in phase transition, we use the Weibull function and Corwin-Ngan function, respectively. Both of them can determine the probability distributions in different phases and the Weibull function shows more reasonable results. Finally, the force distributions are discussed to explain the characteristics of the force chain in the phase transition of granular shear flow. The distribution of the contact force is an indicator to determine the flow phase of granular materials. With the discussions on the statistical properties of the force chain, the phase transition of granular matter can be well understood.