IN SITU SEM MEASUREMENTS OF CRACK CLOSURE FOR SMALL FATIGUE CRACKS IN ALUMINIUM 2024-T351 |
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| Authors: | M. D. Hallday P. Poole P. Bowen |
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| Affiliation: | Interdisciplinary Research Centre in Materials for High Performance Applications and School of Metallurgy and Materials, University of Birmingham, UK;Defence Research Agency, Farnborough, UK |
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| Abstract: | Abstract Crack closure has been measured for a range of small, self-initiated fatigue cracks using in situ SEM loading. Cracks were grown at positive R ratios in the aluminium alloy 2024-T351 and at nominal ΔK levels that extend substantially below the corresponding long crack threshold. The crack closure stress of the small cracks decreased and the Kcl level increased with increasing crack size until the long crack value near threshold was reached. For cracks of depth larger than about one grain size, a good correlation was obtained between small and long crack growth rate data in terms of ΔKeff |
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