Elastic behavior in Contact Dynamics of rigid particles
  The systematic errors due to the practical implementation of the Contact Dynamics method for simulation of dense granular media are examined. It is shown that, using the usual iterative solver to simulate a chain of rigid particles, effective elasticity and sound propagation with a finite velocity occur. The characteristics of these phenomena are investigated analytically and numerically in order to assess the limits of applicability of this simulation method and to compare it with soft particle molecular dynamics. 
Tamas Unger, Lothar Brendel, Dietrich E. Wolf, Janos Kertesz