Crack-Tip Toughness from Vickers Crack-Tip Opening Displacements for Materials with Strongly Rising R-Curves
Abstract:Accurate measurements of the intrinsic crack-tip toughness, K I0, are essential to understanding the strength and toughness of bridging ceramics. Furthermore, even the most carefully made R-curve measurements cannot accurately assess this initial toughness point. In this manuscript, both rigorous and approximate methods are proposed for determining K I0 from crack-tip opening displacement (COD) measurements on Vickers indent cracks for materials with steeply rising R-curves. Such approaches are attractive because of the relative ease of producing indentation cracks and analyzing the CODs; further, the latter method is of particular interest because it saves considerable computational effort. Both the advantages and limitations of the proposed methods are discussed. Finally, based on applying the above methods to three Si3N4 ceramics, it was concluded that there is a common crack-tip toughness of K I0≈2.2±0.3 MPa·√m.
Document Type: Research Article
Affiliations: 1: Institut für Keramik im Maschinenbau, Universität Karlsruhe, Karlsruhe 76131, Germany 2: Institut für keramische Hochleistungswerkstoffe, Technische Universität Hamburg—Harburg, Hamburg 21073, Germany 3: Metals and Ceramics Division, ORNL, Oak Ridge, Tennessee 37831–6068 4: Materials Science, School of Mechanical, Industrial, and Manufacturing Engineering, Oregon State University, Corvallis, Oregon 97331
Publication date: June 1, 2011