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Effect of frequency on high-temperature fatigue crack growth in a silicon carbide reinforced silicon nitride composite

Moffatt, J. E.; Fitzpatrick, M. E. and Edwards, L. (2013). Effect of frequency on high-temperature fatigue crack growth in a silicon carbide reinforced silicon nitride composite. International Journal of Fatigue, 47 pp. 319–329.

DOI (Digital Object Identifier) Link: https://doi.org/10.1016/j.ijfatigue.2012.09.017
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Abstract

A detailed study on a silicon nitride reinforced with silicon carbide whiskers, Si3N4SiCW, has been undertaken at elevated temperature during static and dynamic loading at increasing K and ΔK respectively. It is shown that cyclic sub-critical crack growth rates are lower than static crack growth rates. The increased crack growth rate during static far field loading is attributed to the stress relaxation of the inter-granular glass phase which allows time-dependent processes to occur ahead of the crack tip which lead to enhanced sub-critical crack growth rates. During cyclic fatigue the glass phase has insufficient time to relax and glassy ligaments are able to bridge the crack wake thereby shielding the crack tip from the full force of the applied load. Also, at particular temperatures, bridging between the surfaces of the crack wake by the inter-granular glass phase results in increased strength and fatigue retardation. The extent of ‘crack wake healing’ is shown to be time and temperature dependent. The viscosity of the glass phase is directly related to the temperature and the bonding force associated with glass phase bridging is observed to reduce with increasing temperature. The results from a previous study at room temperature are compared to those found during this investigation.

Item Type: Journal Item
Copyright Holders: 2012 Elsevier Ltd.
ISSN: 0142-1123
Keywords: silicon carbide reinforced silicon nitride; ceramic–ceramic composite; fatigue crack growth; crack healing
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Engineering and Innovation
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 36289
Depositing User: Jim Moffatt
Date Deposited: 23 Jan 2013 16:30
Last Modified: 02 Nov 2017 15:06
URI: http://oro.open.ac.uk/id/eprint/36289
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