Résumé
Dynamical evolution problems concerning collections of rigid bodies are nonsmooth in three respects :
- the mutual impenetrability of the considered bodies or their possible confinement by external boundaries with given motion impose on the configuration parameters $q = (q_1 , \ldots , q_n)$, to remain in a region with corners and edges,
- in the event of a collision, velocity jumps are expected,
- the law of Coulomb, that we shall use for representing dry friction at possible contact points, consists of a nonsmooth relation between local velocities and contact forces.