Frictional powders: Ratchetting under periodic strain in 3D (CD rom Paper no. S 20-5)

The mechanical response of grains under quasi-static cyclic loading is studied by means of a threedimensional Molecular Dynamics scheme. The response of the system is characterized by an accumulation of plastic deformation with increasing number of cycles. From the (deviatoric) stressstrain relation a ratchet-like behavior is observed: Increasing the coefficient of friction leads to a transition from ratcheting to shake-down, i.e., the accumulation of strain stops. The strain rate shows a sharp transition when friction is increases above a certain value, whereas the fraction of sliding contacts shows a smooth, continuous transition, indicating that both effects are decoupled