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Crack‐Tip Toughness from Vickers Crack‐Tip Opening Displacements for Materials with Strongly Rising R ‐Curves
Author(s) -
Fünfschilling Stefan,
Fett Theo,
Oberacker Rainer,
Hoffmann Michael J.,
Schneider Gerold A.,
Becher Paul F.,
Kruzic Jamie J.
Publication year - 2011
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.1551-2916.2010.04329.x
Subject(s) - materials science , toughness , fracture toughness , indentation , composite material , ceramic , crack tip opening displacement , vickers hardness test , displacement (psychology) , fracture mechanics , crack closure , microstructure , psychology , psychotherapist
Accurate measurements of the intrinsic crack‐tip toughness, K I0 , are essential to understanding the strength and toughness of bridging ceramics. Furthermore, even the most carefully made R ‐curve measurements cannot accurately assess this initial toughness point. In this manuscript, both rigorous and approximate methods are proposed for determining K I0 from crack‐tip opening displacement (COD) measurements on Vickers indent cracks for materials with steeply rising R ‐curves. Such approaches are attractive because of the relative ease of producing indentation cracks and analyzing the CODs; further, the latter method is of particular interest because it saves considerable computational effort. Both the advantages and limitations of the proposed methods are discussed. Finally, based on applying the above methods to three Si 3 N 4 ceramics, it was concluded that there is a common crack‐tip toughness of K I0 ≈2.2±0.3 MPa·√m.