Study of High Temperature Failure Mechanisms in Ceramics
Annual rept. Dec 1989-Nov 1990,
SOUTHWEST RESEARCH INST SAN ANTONIO TX
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This annual report documents the results of a basic research program aimed at 1 studying the high temperature failure mechanisms in ceramics, 2 establishing relationships between cavitation mechanisms and creep crack growth characteristics, and 3 developing a damage mechanism-based life prediction model. During the reporting period, the growth rate, near-tip creep responses, and damage processes of creep cracks in a pyroceram glass-ceramic were studied under tensile loading at elevated temperatures. The results of these studies indicated that creep crack growth in the pyroceram glass-ceramic occurred both in continuous and discontinuous manners, with the damage processes manifested as the nucleation, growth, and coalescence of inhomogeneously distributed cavities and microcracks. Sintering of cavities led to the existence of a growth threshold below which the creep crack would open, blunt, but not propagate. Measurements of the total accumulated creep strain near the crack-tip revealed that creep crack extension followed a critical strain criterion. Relationships between cavitation mechanisms and creep crack growth characteristics of the glass-ceramic are discussed.
- Ceramics, Refractories and Glass