Industrial processes in many sectors including pharmaceutical, food, and chemical sectors involve bulk materials with varying degree of cohesivity. Cohesive solids can experience a number of flow problems including arching, ratholing, segregation, channelling and flooding. A better understanding of these problems can help to improve the handling of these solids and provide optimised solutions. The discrete element method (DEM) using soft contact approach as proposed by Cundall and Strack (1979) has been widely used to investigate the behaviour of granular materials subject to a variety of loading conditions. This paper describes a study using DEM to model cohesive-frictional particulate solids. To produce realistic behaviour, the numerical model must capture the decreasing packing density often observed with increasing cohesivity and the cohesive behaviour that is stress history dependent. Whilst the commonly used JMR or DMT models of contact adhesion or the liquid bridge models for capillary action can predict bulk cohesion, they generally have difficulty in capturing the important stress-history dependent behaviour observed in real bulk solids.
In this paper, a simple hysteretic spring model was used to model the elastic-plastic contact deformation, together with an adhesive force model. To elucidate the influence of the DEM contact parameters on the predicted bulk behaviour, this study investigates the relationship between the particle-level plasticity in the model and the predicted bulk plasticity for cohesive materials. In addition, an attempt was made to identify the cause of stress-history dependence from the particle-level properties which provide an effective platform for the further development of this promising model.