Estimation of the High-Temperature R Curve for Ceramics from Strength Measurements Including Specimens with Focused Ion Beam Notches
Abstract:For failure assessment of natural cracks caused by surface treatment, the crack resistance for very small crack extensions is necessary. In ceramics with strongly rising R curves, the initial part of a few micrometer crack propagation is of special interest. For this purpose, the use of very small sharp starter notches introduced by a focused ion beam is recommended. As an example, the initial R curve for gas-pressure-sintered silicon nitride at high temperature will be estimated. Whereas for V-notched bending bars a fracture toughness of about 6–6.3 MPa·m1/2 was determined, the toughness for small strength-relevant cracks was found to be KIc≅5.1 MPa·m1/2.
Document Type: Research Article
Affiliations: 1: Institut für Keramik im Maschinenbau, Karlsruher Institut für Technologie (KIT), Karlsruhe, Germany 2: Institut für keramische Hochleistungswerkstoffe, Technische Universität Hamburg–Harburg, Harburg, Germany 3: Laboratorium für Elektronenmikroskopie, Karlsruher Institut für Technologie (KIT), Karlsruhe, Germany 4: Institut für Struktur- und Funktionskeramik, Montanuniversität Leoben, Leoben, Austria
Publication date: September 1, 2010