R-curve and subcritical crack growth behavior at elevated temperatures in coarse grain alumina

• Published in: Acta materialia 1996-06, Vol.44 (6), p.2259-2264
• Main Authors: Webb, J.E., Jakus, K., Ritter, J.E.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Fatigue, brittleness, fracture, and cracks; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Physics
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/1359-6454(95)00361-4

The effect of temperature and subcritical crack growth on the R-curve of a 99.5% purity coarse grained alumina was studied using chevron-notched, short-bar specimens. Constant loading rate tests were used to measure toughness as a function of crack length and static load tests were used to measure subcritical crack growth as a function of time. It was found that the intrinsic toughness decreased monotonically from 20 to 1200°C while the bridging contribution to the R-curve remained relatively constant over this temperature range. The constant load tests at 700, 1000 and 1200°C showed that substantial subcritical crack growth occurs under static loading. Using the subcritical crack growth parameters derived from these static load tests, the effect of loading rate on R-curve measurement was predicted and compared to experiment. The predicted decrease in the magnitude of the R-curve with a decrease in over five orders of magnitude in loading rate was relatively small compared to experimental scatter.