Fatigue of brittle materials—A critical appraisal

Abstract

Recent demands for high performance ceramics and glass for various applications from bioceramics to cutting tools under fluctuating stress conditions has focussed attention of the scientific community towards fatigue behaviour of brittle solids. Attention to fatigue phenomena in alumina ceramics phenomenological to metals, having an endurance dependent on applied stress with a limit at around 50% of the single cycle fracture stress, was first drawn by the author in late sixties. Slip assisted fatigue process was not considered to be dominant in ceramic materials due to the absence of appreciable crack tip plasticity. With the background of this general survey of fatigue behaviour some fatigue studies based on mode of testing, theoretical and experimental analyses and fractographic evidence have been presented. Studies have shown that there is a dormant period between each successive crack advancement during which the residual stress and a plastic component is built up in a cumulative manner leading to eventual failure. During fatigue$\sigma _{p_j }$ (plastic) and$\sigma _{p_j }$ (residual stress) components are predominant for ductile metals and brittle glass/ceramics respectively.

It is also apparent that dislocation assisted plastic component as a contributing factor in the failure of brittle materials under fatigue cannot be ruled out.