The influence of the indenter tip-radius on indentation testing of brittlematerials

Indentation testing of a brittle material using a notionally 'sharp' indent er may reveal several important physical properties, including fracture tou ghness, surface finish information-and the residual stress state. In the ca se of shallow cone indenters, the contact and fracture mechanics is well de fined and closed-form solutions exist in elasticity theory. However, no rea l indenter is atomically sharp, and the scope of the present article is to quantify how a finite apex radius may modify the stress state induced by a conical indenter. In particular, implications for the load-displacement rel ation, occurrence of yielding and maximum contact pressure induced are foun d. A brief discussion of the influence of edge radius on the flat-ended ind enter, once used to induce Hertzian type ring cracks, is also included, as this may be treated by a similar procedure. (C) 1998 Elsevier Science Limit ed. All rights reserved.