Investigation of cyclic fatigue behaviour of silicon nitride at high temperaturesFunded under: JRC-ADVMAT 1C
A concept for testing brittle materials under uniaxial loading conditions at elevated temperatures is presented. Both static and dynamic loading can be applied, including tension/compression fatigue up to 90 Hz. A heating device has been built, which makes use of high-frequency induction heating to heat electrically non-conducting ceramic specimens to temperatures up to 1400 C in air. Strains are monitored by means of a laser optical extensometer, which does not make physical contact with the specimen. The uniaxial loading concept is tested on a hot pressed Si(3)N(4) material at 1200 C. The same material is used to assess the existence of a cyclic fatigue effect, through a comparison with the lifetime of a statically loaded specimen. The results suggest the existence of a cyclic fatigue effect, with the lifetime being frequency dependent. The lifetime under alternating loads significantly exceeds the static life. This behaviour is interpreted in terms of microstructural aspects of the deformation. At 1200 C the data suggest an endurance limit of sigma = +/- 320 MPa in air. On the basis of the successful uniaxial testing mode concept, proposals for standardisation of, in particular, uniaxial cyclic fatigue testing are made.
Bibliographic Reference: EUR 13349 DE (1991) 141 pp., FS, ECU 11.25
ISBN: ISBN 92-826-2240-1
Record Number: 199110352 / Last updated on: 1994-12-02
Original language: de
Available languages: de