A MODEL FOR THE FATIGUE LIMIT AND SHORT CRACK BEHAVIOUR RELATED TO SURFACE STRAIN REDISTRIBUTION |
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| Authors: | H Abdel-Raouf † T H Topper A Plumtree |
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| Affiliation: | Department of Materials Engineering, Zagazig University, Zagazig, Egypt, Waterloo, Ontario, Canada N2L 3G1;Department of Civil Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1;Department of Mechanical Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1;Currently Visiting Professor at the Department of Mechanical Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1. |
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| Abstract: | A model based on surface strain redistribution and the reduced closure stress of short cracks is shown to successfully predict the fatigue limit and short crack growth behaviour for aluminium alloy 2024-T351. Using this approach, the length of non-propagating cracks can be anticipated. The local stress intensity range may be resolved into two components (first the linear elastic fracture mechanics component and the second is due to surface strain concentration). Consequently, the local stress intensity range of aluminium alloy 2024-T351 is a maximum at a depth of approximately half a grain diameter and a minimum at a depth slightly in excess of three grain diameters. The reduced closure stress for short cracks coupled with the increased applied stress intensity caused by surface strain redistribution accounts for the variation of the effective stress intensity parameter as a function of crack depth. This parameter is a maximum for the smallest possible crack (3 μm) and decreases as crack length increases. |
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