Abstract
In situ scanning electron microscope observations of short crack growth in both a polycrystal 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.
| Original language | English |
|---|---|
| Pages (from-to) | 141-150 |
| Number of pages | 10 |
| Journal | Fatigue and Fracture of Engineering Materials and Structures |
| Volume | 25 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - Feb 2002 |
| Externally published | Yes |
Keywords
- Crack closure
- Grain boundary effect
- In-situ scanning electron microscope fatigue testing
- Microstructurally short cracks
- Slip bands
ASJC Scopus subject areas
- General Materials Science
- Mechanics of Materials
- Mechanical Engineering