SPHERICAL INDENTATION OF HOMOGENOUS AND PLASTICALLY GRADED MATERIALS.
Abstract
This study investigates spherical indentation of plastically graded materials, carburized steels. The hardness of these materials decreases with depth due to micro-structural or compositional changes. In order to predict the behaviour of carburized steels the knowledge of the plastic properties of the surface and the substrate is necessary. It is not possible to obtain those properties with the standard tensile test. The spherical indentation technique can be applied on a superficially heat treated steel in order to obtain its mechanical properties. First spherical indentation is applied to characterize homogenous materials using inverse analysis. The indentation's results are compared to tensile test's results. In a second part spherical indentation is used to characterize carburized steels using inverse analysis in order to obtain plastic properties of the surface. The variation of the plastic properties is considered linear between the surface and the substrate. This variation is defined by the thickness of the surface layer and the thickness of the intermediate layer, those thickness are considered as known. In this part a numerical study is presented in order to understand the influence of the friction and the formation of pile-up and sink-in in plastically graded materials.