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Fracture Mechanics of High‐Toughness Magnesia‐Partially‐Stabilized Zirconia
Author(s) -
Inghels Eric,
Heuer Arthur H.,
Steinbrech Rolf W.
Publication year - 1990
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.1151-2916.1990.tb05262.x
Subject(s) - materials science , crack growth resistance curve , fracture toughness , fracture mechanics , toughness , composite material , cubic zirconia , tetragonal crystal system , crack tip opening displacement , displacement (psychology) , geometry , crack closure , crystallography , mathematics , ceramic , crystal structure , chemistry , psychology , psychotherapist
Crack growth resistance in MgO‐partially‐stabilized ZrO 2 (Mg‐PSZ) has been studied using notched double‐cantilever beams (DCB's). High‐toughness Mg‐PSZ exhibited nonlinear mechanical behavior in the form of residual displacements, related to the transformation of tetragonal ( t ) ZrO 2 precipitates to monoclinic ( m ) symmetry. The influence of this residual displacement on crack resistance behavior (“ R ‐curve” behavior) was analyzed using several different fracture mechanics approaches. Specifically, the “global” resistance W R (Δ a ), a J ‐integral type parameter W J (Δ a ), were determined as a function of crack extension (Δ a ). Some of these parameters displayed a geometry dependence; their form depended on the initial notch depth and the size of the unbroken ligament. The early stages of crack growth were best described by W J (δ a ). The residual strains building up in the wake during crack growth and their effect on specimen displacement made the W R curves (and to some extent the W J curves) dependent on the ratio between initial notch depth and crack extension. The only curves independent of geometry were the G (δ a ) curves, but only in a restricted range of geometry. However, the material resistance of Mg‐PSZ is clearly under‐estimated with such a linear elastic approach.