Chapter 36. Prediction of Creep Deformation of Ceramic Materials Based on the Properties of Grain Boundary Amorphous Phase
- John B. Wachtman Jr.
Published Online: 28 MAR 2008
Copyright © 1993 The American Ceramic Society
Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8
How to Cite
Ding, J. L., Liu, K. C. and Brinkman, C. R. (1993) Prediction of Creep Deformation of Ceramic Materials Based on the Properties of Grain Boundary Amorphous Phase, in Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470314180.ch36
- Published Online: 28 MAR 2008
- Published Print: 1 JAN 1993
Print ISBN: 9780470375266
Online ISBN: 9780470314180
- amorphous phase;
In Ref. 1, a tentative one-dimensional high-temperature deformation and life prediction model was proposed for advanced structural ceramics under general thermal-mechanical loadings. The model was based on the assumption that the time dependence of the material behavior was mainly attributed to the viscosity of the residual amorphous phase along the grain boundaries and that hardening during creep was due to the devitrification of the amorphous phase.
The current work is an attempt to predict the creep deformation of ceramic materials based directly on the microscopic behavior of the amorphous phase. Two different approaches are explored. In one approach, the grain boundary sliding is assumed to be unconstrained. In this case, the resultant shear strain at each grain boundary depends on the resultant shear stress and the viscosity of the amorphous phase, and the overall creep behavior is essentially the average of the resultant shear strain over all the possible grain boundary orientations. In the other approach, the grain boundary sliding is assumed to be constrained by the ceramic grains and crystalline boundary phase. In this case, the ceramic material is treated as a composite and the amorphous phase as the randomly distributed viscoplastic inclusions embedded in an elastic matrix. The overall creep behavior is evaluated with Mori-Tanaka's method combined with Eshelby's solutions for ellipsoidal inclusions. The predicted creep behavior from both approaches will be compared.
Based on the current study, a possible link between the macroscopically observed creep behavior of ceramics and the properties of grain boundary amorphous phase may be established. It will also provide a physical foundation for extending the validity of the aforementioned deformation and life prediction model for one-dimensional to three-dimensional loadings. This extension is necessary for practical reliability analysis of ceramic structures.