The In ̄uence of the Indenter Tip-Radius on Indentation Testing of Brittle Materials

Indentation testing of a brittle material using a notionally `sharp' indenter may reveal several important physical properties, including fracture toughness, surface ®nish information and the residual stress state. In the case of shallow cone indenters, the contact and fracture mechanics is well de®ned and closed-form solutions exist in elasticity theory. However, no real indenter is atomically sharp, and the scope of the present article is to quantify how a ®nite apex radius may modify the stress state induced by a conical indenter. In particular, implications for the load-displacement relation, occurrence of yielding and maximum contact pressure induced are found. A brief discussion of the in ̄uence of edge radius on the ̄at-ended indenter, once used to induce Hertzian type ring cracks, is also included, as this may be treated by a similar procedure. # 1998 Elsevier Science Limited. All rights reserved