Experimental and numerical analyses of instrumented and continuous indentation of treated steels

The present paper uses the indentation of materials with a yield strength gradient, by spherical indenters in order to obtain Vickers hardness profile. Using finite element modelling, a simulation of elasto-plastic spherical indentation of materials with a yield stress was carried out. A theoretical model for effective mean pressure evolution of the spherical indentation on the surface of heat treated steels was obtained. Using the preceding model and steepest descent optimisation algorithms, a method for determining Vickers hardness profile (surface hardness and layer thicknesses) of these steels, is given. Results for carbo-nitriding steels obtained by the standard Vickers micro-hardness techniques (on the section taken through the surface) are compared with those obtained by the proposed method.