Variational approach to contact problems in nonlinear elasticity

We use variational methods to study problems in nonlinear 3-dimensional elasticity where the deformation of the elastic body is restricted by a rigid obstacle. For an as-signed variational problem we first verify the existence of constrained minimizers whereby we extend previous results with different respects. Then we rigorously derive the Euler-Lagrange equation as necessary condition for minimizers, which was possible before merely with strong hypothetical smoothness assumptions for the solution. The Lagrange multi-plier corresponding to the obstacle constraint provides structural information about the nature of frictionless contact and, in the case of contact with, e.g., a corner of the ob-stacle, we derive a qualitatively new contact condition taking into account the deformed shape of the elastic body. By our rigorous analysis it is shown the first time that energy minimizers really solve the mechanical contact problem.