Coefficient of tangential restitution for viscoelastic spheres

摘要

The collision of frictional granular particles may be described by an interaction force whose normal component is that of viscoelastic spheres while the tangential part is described by the model by Cundall and Strack (Geotechnique 29, 47 (1979)) being the most popular tangential collision model in Molecular Dynamics simulations. Albeit being a rather complicated model, governed by 5 phenomenological parameters and 2 independent initial conditions, we find that it is described by 3 independent parameters only. Surprisingly, in a wide range of parameters the corresponding coefficient of tangential restitution, epsilon(t), is well described by the simple Coulomb law with a cut-off at epsilon(t) = 0. A more complex behavior of the coefficient of restitution as a function on the normal and tangential components of the impact velocity, g(n) and g(t) , including negative values of epsilon(n) , is found only for very small ratio g(t)/g(n). For the analysis presented here we neglect dissipation of the interaction in normal direction.