A method to take account of the geometrical imperfections of quasi-spherical indenters

International audiencePerfect indenter geometry is quite difficult to manufacture, especially in the nano and macro scales. Indentation curves obtained with imperfect indenter geometry can show strong differences with those obtained with assumed perfect indenter geometry, thereby leading to erroneous data exploitation results. This numerical study brings out the effect of imperfect spherical indenter geometry on indentation load-penetration depth curves, and on the mechanical properties identified by a reverse analysis model based on ideal spherical geometry. It is shown that a method to take account of geometrical imperfections is essential. Two correction methods based on geometrical and physical considerations are assessed, as well as the relevance of the use of the penetration data or the contact data. A method based on the equality of mean contact pressures and indenter volumes under the contact surface is found to be most relevant, as confirmed by the quality results obtained after application of a reverse analysis model. The proposed method is of particular interest in the case of the use of an imperfect indenter whose profile is accurately known