1 Powder Flow Testing with Biaxial and Triaxial devices

The mechanical response of grains under quasi-static cyclic loading is studied by means of two-and three-dimensional Molecular Dynamics (also called discrete element method). The response of the system is characterized by elastic behavior, softening, plastic yield and critical state flow. Yield is reached for some deformation, and when the contact friction is stronger plastic yield is reached for larger deformation amplitude. In the case of no yield, after many cycles of deformation, accumulation of irreversible plastic strain with the number of cycles is found. For the deviatoric stress and strain, a quasi-periodic ratchet-like behavior is observed. Simulations with different coefficients of friction show weaker plastic strain accumulation in the presence of stronger friction