We consider a frictionless contact problem, Problem
, for elastic materials. The process is assumed to be static and the contact is modelled with unilateral constraints. We list the assumptions on the data and derive a variational formulation of the problem, Problem
. Then we consider a perturbation of Problem
, which could be frictional, governed by a small parameter
. This perturbation leads in a natural way to a family of sets
. We prove that Problem
is well-posed in the sense of Tykhonov with respect to the family
. The proof is based on arguments of monotonicity, pseudomonotonicity and various estimates. We extend these results to a time-dependent version of Problem
. Finally, we provide examples and mechanical interpretation of our well-posedness results, which, in particular, allow us to establish the link between the weak solutions of different contact models.