Numerical study on influence of particle shape and deformation on friction behavior of flexible cylindrical particle flows

A discrete element method (DEM) model for deformable particles is established and adopted to investigate the Jenike shear process of flexible cylindrical particles with different aspect ratios (4 < Ar < 6). The DEM model is firstly validated against both experimental data and analytic solutions. Then, numerical simulations are carried out and the effects of particles shape and deformation on their friction behavior are investigated through a particle-scale analysis on particle deformation, coordinate number, contact forces, orientation and internal friction angle. Comparative results between flexible and rigid particles under the same conditions show that the shear stress increases almost linearly with the normal load regardless of particle stiffness or shape. For both rigid and flexible particles, the shear stress and internal friction angle increase with Ar. The shear stress and internal friction angle of the flexible particles are higher than those of the rigid ones especially when Ar = 6. The latter has more inter-particle contacts but the former has stronger contact forces. When Ar = 4 and 5, the flexible particles without many initial deformations will deform significantly during the shear process with a complex reconfiguration taking place. However, when Ar = 6, the initial deformation and internal forces of the flexible particles only change slightly during the shear process. It is thus believed that the high shear stress and internal friction angle of the flexible particles with Ar = 6 are caused by their solid packing structure which strongly enhances the capability of the particle flow to resist shear. The current knowledge will be helpful for improving the kinetic theories for granular flow for complex irregular particle flows.