R-Curve Determination for the Initial Stage of Crack Extension in Si3N4
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Autor:
Fett, T; Fünfschilling, S; Hoffmann, MJ; Oberacker, R; Jelitto, H; Schneider, GA
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Quelle:
JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 2008, Band 91, Heft 11, S. 3638-3642
Abstract
In experimental R-curve investigations crack development usually starts
from notches. The validity of R-curves depends on the size of the notch
root radius. This influence is ignored in many cases. In this study it
will be shown how the notch radius affects the formally computed crack
resistance curve and how the initial true R-curve can be obtained from
the same data. The tests were performed on a silicon nitride with 5 wt%
Y2O3 and 2 wt% MgO. The evaluation of load versus displacement
measurements during fracture showed a very steep R-curve with the
saturation reached even after about 10 μm crack extension.