Estimation of the High-Temperature R Curve for Ceramics from Strength Measurements Including Specimens with Focused Ion Beam Notches
- Author: S. Fuenfschilling, T. Fett, M.J. Hoffmann, R. Oberacker, H. Oezcoban, G.A. Schneider, P. Brenner, D. Gerthsen, R. Danzer
- Source: JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 2010, Band 93, Heft 9, S. 2411-2414
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 center dot m1/2 was determined, the toughness for small strength-relevant cracks was found to be K-Ic congruent to 5.1 MPa center dot m1/2.