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Cyclic Fatigue from Frictional Degradation at Bridging Grains in Alumina
Author(s) -
Lathabai Srinivasarao,
Rödel Jürgen,
Lawn Brian R.
Publication year - 1991
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.1151-2916.1991.tb04109.x
Subject(s) - materials science , composite material , bridging (networking) , indentation , fracture mechanics , scanning electron microscope , tension (geology) , ceramic , toughness , cyclic stress , intergranular corrosion , fracture toughness , brittleness , crystallite , forensic engineering , metallurgy , corrosion , ultimate tensile strength , computer network , computer science , engineering
Tension—tension cyclic loading tests have been conducted on a coarse‐grained alumina ceramic that exhibits toughnesscurve behavior by grain‐interlock bridging. Fatigue effects are observed in the regions of both short cracks, using indentation flaws, and long cracks, using compact‐tension specimens. A true mechanical fatigue effect is demonstrated by running the tests below the static fatigue limit. A custom‐made device for in situ observation of crack propagation in the scanning electron microscope enables us to identify bridge degradation as a cause of the fatigue process. “Wear” debris cumulates at the sliding intergranular frictional contact points, indicating a loss of traction at the junction. The basis of a fracture mechanics model describing the effect of this frictional degradation in reducing crack‐tip shielding is outlined and fitted to the data. It is suggested that the bridge degradation fatigue mechanism may be widespread in polycrystalline ceramics with pronounced toughness curves.