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Creep and Creep Fracture in Hot‐Pressed Alumina
Author(s) -
Robertson A. Gordon,
Wilkinson David S.,
Cáceres Carlos H.
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.tb04322.x
Subject(s) - creep , materials science , flexural strength , composite material , tension (geology) , stress (linguistics) , fracture (geology) , ultimate tensile strength , diffusion creep , bending , microstructure , grain boundary , linguistics , philosophy
The creep and creep fracture behavior of two hot‐pressed aluminas are presented, for both flexural and tensile testing. Steady‐state power‐law creep is observed with a stress exponent of about 2 for each material. Three distinct fracture regimes are found. At high stress in flexure, fracture occurs by slow crack growth with a high stress dependence of the failure time. At intermediate stresses, in both flexure and tension, creep fracture occurs by multiple microcracking after modest strains. Failure times exhibit a modest stress dependence (stress exponent of 2.5 in tension and 3 in flexure), with a constant failure strain equal to 0.09. The failure times are considerably longer in flexure than in tension, because of the constraint imposed on crack growth by the bending geometry. We conclude that flexure cannot be used for creep lifetime assessment, even in simple, single‐phase materials such as Al 2 O 3 . At low stresses, in tension, failure also exhibits a modest stress dependence but with a much higher failure strain. The material shows the onset of super‐plastic behavior.