Developments of Ultra High Temperature-Extensometer and High Temperature Inelastic Design Method of Ceramics Using It

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In the present study, we developed the testing system for evaluating accurately the push-pull cyclic fatigue strength of ceramics at elevated temperatures. This system was composed of the closed loop type-electrohydraulic testing system, the electric furnace with the KANTHAL SUPER 33 as a heater and the water-cooled specimen gripping device which was newly designed with the Ni-based heat-resisting super alloy The push-pull cyclic fatigue tests were successfully performed for the sintered silicon nitride ceramics in the temperature range from room temperature to 1200ﾟC by means of this testing system.Furthermore, we designed the new extensometer for measuring tensile and compressive deformations of ceramics at elevated temperatures. The tensile and compressive displacements of sintered silicon nitride ceramics were measured by means of this extensometer under stress rate-controlled triangular stress wave at room temperature. The lever-type extensometer proved to be useful for measuring tensile and compressive displacements with sufficient precision at room temperatures.