Indentation of rigid cones into conical holes molded in elastic blocks

Abstract

Results obtained from several series of experiments on the normal loading of rigid spherical and conical indenters onto elastic blocks are described. Different series of experiments conducted are (1) normal loading of a rigid sphere onto elastic blocks of polydimethylsiloxane of different elastic moduli, (2) normal loading of rigid cones of different included angles onto a flat of the elastic blocks, and (3) normal loading of rigid cones of different included angles into conical holes of various included angles molded in the two types of elastic block. It was found that the indenter load versus indenter displacement data corresponding to the normal loading of the sphere and cones of different included angles onto a flat surface of the elastic blocks were very well fitted by the theories of Hertz and Sneddon, respectively. It has also been found that when rigid cones were loaded into conical holes molded in the elastic blocks, the load versus indenter displacement data were not fitted by the Sneddon theory for a conical indenter loading onto an elastic half space. Neither were the experimental data fitted by a modified Sneddon equation in which the effective semi included angle β of the conical indenter was taken as β=[(π∕2)−(α′−α)], with α′ and α being the semi-included angles of the conical hole and the indenter, respectively. These results cast some doubt on the validity of some of the current methods in use for analyzing the unloading curves obtained from nanoindentation experiments made using pointed pyramidal and conical indenters on elastic-plastic solids.