On enhanced descend algorithms for solving frictional multi-contact   problems : applications to the Discrete Element Method
  In this article, we present various numerical methods to solve multi-contact problems within the Non-Smooth Discrete Element Method. The techniques considered to solve the frictional unilateral conditions are based both on the bi-potential theory and the Augmented Lagrangian theory. A new Newton method is developed to improve the classical algorithms. 
Serge Dumont (LAMFA)
math.NA physics.class-ph