Premium
Retardation of Fatigue Crack Growth in Ceramics by Glassy Ligaments: A Rationalization
Author(s) -
Ramamurty Upadrasta
Publication year - 1996
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1996.tb08529.x
Subject(s) - materials science , ceramic , bridging (networking) , composite material , cavitation , crack closure , stress intensity factor , fracture mechanics , paris' law , amorphous solid , crack growth resistance curve , mechanics , crystallography , computer network , chemistry , physics , computer science
In high‐temperature fatigue crack growth (FCG) experiments on ceramic materials containing amorphous grain boundary phases, the crack growth rates under cyclic loads were observed to be lower than those predicted solely on the basis of crack growth velocities measured under static loads. In this paper, a rationalization was offered for such a behavior by means of a phenomenological glass‐bridging model which takes the relaxation behavior of glass into account. In ceramics which exhibit subcritical crack growth through cavitation ahead of the crack tip, the maximum stress intensity factor of the fatigue cycle required to initiate FCG was observed to be always greater than or equal to the threshold stress intensity factor for crack growth under sustained far‐field loads. This trend was also explained with the aid of the glass‐bridging model and invoking the equivalence between bridging and damage zones. The elevated temperature FCG behavior of nitride‐based ceramics which exhibit grain bridging in the wake during crack propagation was discussed and contrasted with oxide‐based ceramics which show glass bridging.