Chapter 46. Environmental Effects on Crack Propagation of Alumina Ceramics
- Todd Jessen,
- Ersan Ustundag
Published Online: 28 MAR 2008
Copyright © 2000 The American Ceramic Society
24th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: B: Ceramic Engineering and Science Proceedings, Volume 21, Issue 4
How to Cite
Ebrahimi, M. E., Chevalier, J. and Fantozzi, G. (2008) Environmental Effects on Crack Propagation of Alumina Ceramics, in 24th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: B: Ceramic Engineering and Science Proceedings, Volume 21, Issue 4 (eds T. Jessen and E. Ustundag), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470294635.ch46
- Published Online: 28 MAR 2008
- Published Print: 1 JAN 2000
Print ISBN: 9780470375693
Online ISBN: 9780470294635
- crack propagation;
- high purity alumina;
- double torsion;
- water molecules;
- ceramic materials
The crack propagation behavior of alumina with grain sizes ranging from 2–53 pm was studied. A high purity alumina (<99.99 %) and an alumina with 500 ppm MgO were used as starting powders.
The results obtained by Double Torsion in different environments (air, water and silicon oil), show that slow crack growth is due to stress corrosion by water molecules at the crack tip. Region I and II of crack propagation are very sensitive to the humidity and region III is independent of the environment.
The slope of V-KI curve (crack velocity versus applied stress intensity factor) depends strongly on the amount of rising crack resistance (R-curve) with crack extension. The higher the R-curve effect, the higher is the slope. It appears that crack resistance increases with grain size from 2 to 35 pm, as a consequence of bridging mechanisms. Above 35 μm, a transition from intergranular towards transgranular fracture occurs, accompanied by a decrease of R-curve effect. When the R-curve is taken into account, a unique V-Kltip (crack velocity versus crack tip stress intensity factor) curve is obtained, independently of grain size.