Analytical and experimental elastoplastic spherical indentations of a layered half-space

This paper presents an analytical model for the elastoplastic spherical indentation of smooth coated spheres. In this model, only the coating deforms plastically, while the bulk materials remain elastic. This model takes into account the elastic properties of the spheres and the elastic then elastoplastic behaviour of the coating. Two sets of interface conditions were investigated. In one, the coating is freely laid on its substrate; in the other the coating is bonded to it. The coating was modeled using a thin layer assumption. The model provides a prediction of the contact radius under load. A specifically designed experimental apparatus is then presented and experimental data are analysed. Tests were carried out for silver, copper, aluminium and zinc layers of thicknesses ranging from 20 μm to 500 μm. Spherical indenters radii were 0.5, 1, or 2.5 mm and the interfaces were free or bonded. Comparisons between analytical and experimental results showed a good agreement, even for experimental conditions beyond the thin layer assumption.