The influence of initial elastic surface stresses on instrumented sharp indentation

The present work examines the influence of pre-existing, elastic surface stresses on instrumented sharp indentation. The surface is modeled as a homogeneous and isotropic elastoplastic solid in the context of linear elasticity and Mises plasticity with isotropic strain hardening and associative flow rule. Prior to indentation, a homogeneous, biaxial, elastic stress state may exist in the substrate. The influence of the initial elastic surface stresses on the force-depth response of instrumented sharp indentation tests, such as Vickers and Berkovich, was analyzed. The unique connection of the indentation loading response and the average initial stress is based on a relation of the stresses right under the indenter which holds universally for nearly incompressible materials.