Relaxation procedures for solving Signorini?Coulomb contact problems

This paper deals with the numerical solution of two-dimensional unilateral contact problems with friction between a linearly elastic body and a rigid obstacle. The contact is modeled by Signorini's law and the friction by Coulomb's law. A discrete dual formulation condensed on the contact zone is introduced and the contact forces are obtained either by relaxation or by block-relaxation procedures. A comparison is presented between these two techniques