Quasi-static contacts

We recall briefly the Hertz theory of elastic contact. Diverse extensions including adhesion, or solid friction at the contact zone are briefly discussed. Other behavior laws than elasticity (plasticity, damage, fracture, visco-elasticity) are examined to analyse the limitation of the hertzian description. We also briefly mention some other phenomena which interfere with this simple picture (large deformation, elasto-hydrodynamic effects, roughness). All this material is presented at a very elementary level, only resorting to scaling in order to underline the most salient features of this vast phenomenology.