Cyclic fatigue crack growth from indentation flaw in silicon nitride: Influence of effective stress ratio

Journal Article · Tue Nov 01 04:00:00 EST 1994 · Acta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-7151(94)90449-9· OSTI ID:6894326

Choi, G; Kawabe, Yoshikuni ^[1]; Horibe, Susumu ^[2]

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1. National Research Inst. for Metals, Ibaraki (Japan). Tsukuba Labs.
2. Waseda Univ., Tokyo (Japan). Dept. of Materials Science and Engineering

The characteristics of cyclic fatigue crack growth in a silicon nitride which hardly shows rising R-curve behavior were investigated by using specimens having an indentation-induced flaw. V-shaped behavior was observed in the relation between the maximum stress intensity factor K[sub max] and crack growth rate. When a crack growth rate is plotted as a function of the effective maximum stress intensity factor K[sub eff,max] which takes account of the residual crack opening stress component K[sub r] in addition to K[sub max], crack growth behavior is expressed by a power law relationship for the region above a crack length of about 0.37 mm in this experiment. However, it deviates from this relation below the critical length. Such crack growth behavior is explicable by introducing the term of the effective stress ratio R[sub eff] defined as (K[sub min] + K[sub r])/(K[sub max] + K[sub r]). Crack growth behavior in the terms of K[sub eff,max] and R[sub eff] is expressed by a unique growth law, irrespective of crack length, i.e. da/dN = C(K[sub eff,max])[sup 30]([Delta]K[sub eff])[sup 5], where [Delta]K[sub eff] = (1 [minus] R[sub eff])K[sub eff,max]. Such behavior is consistent with that in the specimen containing a through-thickness crack. This equation indicates that fatigue crack growth rate in the present material is particularly sensitive to K[sub eff,max], and less sensitive to [Delta]K[sub eff].

• OSTI ID: 6894326
• Journal Information: Acta Metallurgica et Materialia; (United States), Journal Name: Acta Metallurgica et Materialia; (United States) Vol. 42:11; ISSN 0956-7151; ISSN AMATEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
CRACK PROPAGATION
DATA
DEFECTS
EXPERIMENTAL DATA
FATIGUE
INFORMATION
MECHANICAL PROPERTIES
NITRIDES
NITROGEN COMPOUNDS
NUMERICAL DATA
PNICTIDES
RESIDUAL STRESSES
SILICON COMPOUNDS
SILICON NITRIDES
STRESSES