An efficient and reliable residual-type a posteriori error estimator for the Signorini problem

We derive a new a posteriori error estimator for the Signorini problem. It generalizes the standard residual-type estimators for unconstrained problems in linear elasticity by additional terms at the contact boundary addressing the non-linearity. Remarkably these additional contact-related terms vanish in the case of so-called full-contact. We prove reliability and efficiency for two- and three-dimensional simplicial meshes. Moreover, we address the case of non-discrete gap functions. Numerical tests for different obstacles and starting grids illustrate the good performance of the a posteriori error estimator in the two- and three-dimensional case, for simplicial as well as for unstructured mixed meshes.