Characteristics of force transmission in cohesive agglomerates impacting a rigid surface

Abstract

We numerically analyze the characteristics of force transmission in a single wet particle agglomerate composed of spherical particles impacting a flat surface for a broad range of values of the cohesive force induced by the binding liquid and the initial falling speed of agglomerate by using an extensive discrete element method. The numerical method considers the spherical particles as rigid grains with the inclusion of the reversible capillary bonds between primary particles, each capillary bond induces the normal capillary attraction force and the normal viscous force. In this impact test, the force transmission characterized by the probability density function of the normal forces (tensile and compressive components) and the frictional forces which control the behavior of the early-stage impact and the early-stage deposition that observed from the mechanical responses of such agglomerate. We show that the force distribution strongly depends on the cohesive force and the impact velocity at the early-stage impact, whereas it is nearly independent at the early-stage deposition of agglomerate. In early-stage impact, in particular, the width of the positive and negative ranges of normal forces is inversely proportional to the cohesive force, the density of the normal compressive forces and tangential forces is inversely proportional to the cohesive force, whereas this density increases with increasing the impact velocity. Remarkably, by continue normalizing the normal and tangential forces by a speed ratio, defined as a ratio of the impact speed obtained at its first touching with the flat and gravitational particle velocity, all the probability density functions of normal and tangential forces collapsed on a single curve.