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- Title
In situ investigation of small fatigue crack growth in poly-crystal and single-crystal aluminium alloys.
- Authors
Zhang, X. P; Wang, C. H; Ye, L; Mai, Y. -W
- Abstract
Abstract In situ scanning electron microscope observations of short crack growth in both a poly-crystal and a single-crystal alloy revealed that fatigue cracks may grow in a shear decohesion mode over a length that is several times the grain size, far beyond the conventional stage I regime. In the poly-crystal aluminium alloy 2024-T351, fatigue cracks were found to continue to grow along one shear band even after two mutually perpendicular shear bands had formed at the crack tip. For the single-crystal alloy specimen with the loading axis being nearly perpendicular to its main shear plane, mode I fatigue cracks were found to grow along the shear band. These two types of fatigue crack growth pose a significant challenge to the existing fatigue crack growth correlating parameters that are based on crack-tip opening displacement. In particular, it has been found that the cyclic crack-tip opening displacement, which accounts for both large-scale yielding and the lack of plasticity-induced crack closure, is unable to unify the growth rates of short and long cracks in aluminium 2024-T351, suggesting a possible dependence of crack growth threshold on crack length.
- Subjects
ALUMINUM alloy fatigue; METAL crystals
- Publication
Fatigue & Fracture of Engineering Materials & Structures, 2002, Vol 25, Issue 2, p141
- ISSN
8756-758X
- Publication type
Article
- DOI
10.1046/j.8756-758x.2001.00484.x