Bending and twisting friction models in soft-sphere discrete element simulations for static and dynamic problems

•DEM model with shear, rolling (bending and twisting) frictional forces is presented.•Improved predictions obtained for a modified bending friction formulation.•Effects of bending/twisting in static and dynamic test cases are demonstrated.•Effects of dampening in static and dynamic test cases are demonstrated.

In soft-sphere discrete element models of granular flow, particles may interact in a variety of ways including interactions normal to points of contact and interactions tangential to points of contact such as sliding, rolling, bending and twisting. In the majority of models normal and sliding modes are used. Rolling friction is sometimes reported but incorporation of bending and twisting effects is less common. In this paper it is shown that the precise mathematical nature of bending and twisting models in soft-sphere simulations can have significant effects on model predictions, especially for the case of dynamic granular flow problems.