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Sigmoidal Indentation–Strength Characteristics of Polycrystalline Alumina
Author(s) -
Cook Robert F.,
Liniger Eric G.,
Steinbrech Rolf W.,
Deuerler Friederike
Publication year - 1994
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.1151-2916.1994.tb06997.x
Subject(s) - indentation , materials science , composite material , fracture toughness , cantilever , toughness , cracking , crystallite , flexural strength , fracture mechanics , beam (structure) , structural engineering , metallurgy , engineering
The fracture properties of a series of three polycrystailine aluminas are examined using indentationstrength and double cantilever beam techniques. The indentation‐strength response is shown to be sigmoidal with concave‐down behavior at small indentation loads and concave‐up behavior at large indentation loads. A model is developed for the general response, combining increasing toughening by ligamentary bridging at small crack lengths and increasing residual‐stress relief by lateral cracking at large indentation loads. The model is fit to the strength data and used to deconvolute the underlying toughness variation and predict the intrinsic strength of the materials. Direct measurements of toughness using the “long‐crack” double cantilever beam geometry are shown to overestimate the toughness variations effective during “short‐crack” strength tests.