Analyse par simulation numérique de l'influence du facteur de correction sur les mesures de dureté de matériaux élasto-plastiques en indentation instrumentée

Measurements of mechanical properties by instrumented indentation rely heavily upon the relationship between the unloading contact stiffness, S _u, the projected contact area, A_c, and the reduced modulus, E_r. This relationship is written in the form S_u = 2βE_r(A_c/π)^1/2, where β is a correction factor that depends on the material properties, the geometry of the indenter and also the penetration depth. In practice, the correction factor is generally assumed constant for a given tip geometry. However, numerical simulations of indentation test performed on purely elastic materials have evidenced that β strongly depends on the penetration depth/tip radius ratio. In this work, the dependence of β on the penetration depth and tip blunting is studied by FEA in the case of elastic-plastic materials generally encountered in engineering. The consequence of not taking into account the influence of β on hardness measurements is also investigated.