Interprétation du module d'indentation dans le cas des matériaux anisotropes et/ou actifs
Résumé
The aim of this paper consists in the understanding and in the analysis of the indentation modulus values M⟨hkl⟩ determined by the continuous stiffness method in the case of anisotropic materials and/or SMART materials as ferroelectric or shape memory alloys. Some examples have been studied; Ni, W, Zn, Ni2 MnGa and PZT where the indentation modulus values are very different to those given by the biaxial modulus (E/1−ν2). A simple analytical formulation which gives results very close to those obtained by 3D finite elements calculations of Berkovich indentation of materials with cubic and hexagonal symmetries has been proposed. An interpretation of the two indentation modulus values of SMART materials under loading or at 90% of unloading has been proposed. These two values are linked to the modification or the reorientation of the ferroelectric domains or of the martensite variants under the pressure of the tip. In conclusion, the indentation modulus is far to be a standard parameter, that is to say the biaxial modulus, when the studied materials present a great anisotropy or behave as SMART materials.