Preparation of Ultra-High-Temperature Push-Pull Thermal Fatigue Testing Equipment for Ceramics and Development of Evaluation Methods of their Strength.

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1. Push-pull thermal fatigue testing equipment was debeloped for evaluating the strength of ceramic materials at ultra-high-temperatures. The push-pull axis was specially aligned in order to avoid bending moment subjected to the ceramic specimen. Strain measurement was done by means of noncontact laser dimensional sensor (Ohtani).2. High-temperature faituge tests were conducted by a similar testing machine of the push-pull type with different frames, heating system, and extensometer. It was proved that the test results on ceramics were coinside with those obtained from the debeloped equipment (Nitta).3. It was found that the impact fravture strength of ceramics at high temperatures was not inferior to the static fracture strength. Also an estimating method of the ceramics strength was studied to find out the common property parameters independent of testing method and specimen shape and size (Muramatsu).4. A reliable relationship betewwn fracture stress and small flaw size for ceramics was obtained, which was quite important and useful for evaluating the flaws in ceramics (Usami).5. Stable crsck growth in ceramics was observed at high temperature during loading tests in a specially designed scanning electron microscope (Kitagawa).6. Thermal fatigue tests were conducted on high-strength, low-ductility nickel base superalloys, and their failure analysis and the design of gas-turbines were practiced (Sakon).7. A stochastic approach based on Monte Carlo simulation was preformed in order to clarify the behavior of small crack initiation and propagation in creep-fatigue condition. A probabilistic approach to the spacial distribution of creep cavities was also carried out for establishing a stochastic damage mechanics (Ohtani and Kitamura).