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Determination of Threshold Stress Intensity for Crack Growth at High Temperature in Silicon Carbide Ceramics
Author(s) -
MINFORD ERIC J.,
TRESSLER RICHARD E.
Publication year - 1983
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.1151-2916.1983.tb10044.x
Subject(s) - materials science , stress intensity factor , silicon carbide , intensity (physics) , stress (linguistics) , ceramic , composite material , stress relaxation , fracture (geology) , metallurgy , fracture mechanics , creep , optics , linguistics , philosophy , physics
A method for estimating the threshold stress intensity for crack growth is presented. The technique requires prior knowledge of the flaw population of a material and uses applied static loads followed by fast fracture to assess the effect of initial applied stress intensity on flaw behavior. The technique was applied to a hot‐pressed Sic at 1200° and 1400°C in a nonoxidizing atmosphere. At 1400°C with a static load time of 4 h, the threshold stress intensity was determined to be ∼ 1.75 MPa·m 1/2 with a slight tendency toward higher fracture stress with increasing initial stress intensity below the threshold. At 1200°C for a static load time of 4 h, apparent strengthening was observed below a threshold stress intensity of ∼2.25 MPa·m 1/2 . This strengthening effect appears to result from stress relaxation in the crack‐tip region, probably by plastic deformation which involves the oxide grain‐boundary phase.