Micro-indentation tests seem to be a promising way of obtaining material characteristics of brittle materials, such as fuel pellets of Pressurized Water Reactors, for which the usual traction tests can not be performed. Since analytical formulas are limited to simple constitutive laws, one has to use an inverse problem theory to obtain elasto-visco-plastic characteristics. This requires an efficient description of the mechanical phenomena through finite element calculations, with a particular emphasis on contact modelling. This paper presents a master-slave algorithm allowing to treat frictionless contact problems with large slip between surfaces. In the context of the Newton's method used to solve the equilibrium, an active set method is used to solve the system including the contact inequalities. This method is validated by comparing numerical results to theoretical and experimental ones.

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