High-temperature crack growth in monolithic and SiC[sub w]-reinforced silicon nitride under static and cyclic loads

Journal Article · Tue Nov 01 00:00:00 EST 1994 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1994.tb04535.x· OSTI ID:6609482

Ramamurty, U ^[1]; Hansson, T ^[2]; Suresh, S ^[3]

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1. Univ. of California, Santa Barbara, CA (United States). Materials Dept.
2. Nagaoka Univ. of Technology (Japan). Dept. of Mechanical Engineering
3. Massachusetts Inst. of Technology, Cambridge, MA (United States). Dept. of Materials Science and Engineering

Experimental results are presented on subcritical crack growth under sustained and cyclic loads in a HIPed Si[sub 3]N[sub 4] at 1,450 C and a hot-pressed Si[sub 3]N[sub 4]-10 vol% SiC[sub w] composite for the temperature range 1,300--1,400 C. Static and cyclic crack growth rates are obtained from the threshold for the onset of stable fracture with different cyclic frequencies and load ratios. Fatigue crack growth rates for both the monolithic and SiC[sub w]-reinforced Si[sub 3]N[sub 4] are generally higher than the crack growth velocities predicted using static crack growth data. However, the threshold stress intensity factor ranges for the onset of crack growth are always higher under cyclic loads than for sustained load fracture. electron microscopy of crack wake contact and crack-tip damage illustrate the mechanisms of subcritical crack growth under static and cyclic loading. Critical experiments have been conducted systematically to measure the fracture initiation toughness at room temperature, after advancing the crack subcritically by a controlled amount under static or cyclic loads at elevated temperatures. Results of these experiments quantify the extent of degradation in crack-wake bridging due to cyclically varying loads. The effects of preexisting glass phase on elevated temperature fatigue and fracture are examined, and the creep crack growth behavior of Si[sub 3]N[sub 4]-based ceramics is compared with that of oxide-based ceramics.

• OSTI ID: 6609482
• Journal Information: Journal of the American Ceramic Society; (United States), Vol. 77:11; ISSN 0002-7820
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COMPOSITE MATERIALS
CRACK PROPAGATION
FRACTURE MECHANICS
SILICON CARBIDES
SILICON NITRIDES
CRACKS
EXPERIMENTAL DATA
FATIGUE
HOT PRESSING
STATIC LOADS
STRESS INTENSITY FACTORS
CARBIDES
CARBON COMPOUNDS
DATA
FABRICATION
INFORMATION
MATERIALS
MATERIALS WORKING
MECHANICAL PROPERTIES
MECHANICS
NITRIDES
NITROGEN COMPOUNDS
NUMERICAL DATA
PNICTIDES
PRESSING
SILICON COMPOUNDS
360203* - Ceramics
Cermets
& Refractories- Mechanical Properties
360603 - Materials- Properties