Near-threshold crack extension mechanisms in an aluminum alloy studied by SEM and X-ray tomography
| Autor: | Fatih Buelbuel, Angelika Brueckner-Foit, Marcel Wicke, Martina Zimmermann, Tina Kirsten, Hans-Juergen Christ |
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| Rok vydání: | 2019 |
| Předmět: |
Materials science
Mechanical Engineering Alloy X-ray chemistry.chemical_element 02 engineering and technology engineering.material 021001 nanoscience & nanotechnology Cyclic compression Industrial and Manufacturing Engineering Near threshold 020303 mechanical engineering & transports 0203 mechanical engineering chemistry Mechanics of Materials Aluminium Modeling and Simulation mental disorders Fracture (geology) engineering General Materials Science Tomography Composite material 0210 nano-technology |
| Zdroj: | International Journal of Fatigue. 119:102-111 |
| ISSN: | 0142-1123 |
| DOI: | 10.1016/j.ijfatigue.2018.08.024 |
| Popis: | The crack extension behavior of long cracks in the near-threshold regime is analyzed at R = 0.1 using flat dog-bone specimens of a commercial aluminum alloy in peak-aged and overaged condition. Once a pre-crack had been introduced by cyclic compression, experiments were performed at nominally constant ΔK-values close to the threshold initially determined by continuous load increase. Analyses of the fractured specimens in SEM and µ-CT show that two major mechanism caused the cracks propagating in an intermittent way. First, the crack front was pinned by primary precipitates leading to ductile bridges on the fracture surfaces. Overaging was observed to generally enhance the pinning potential of the precipitates. The second mechanism was crack extension in a shear-dominated mode but dissimilar to stage-I crack growth. This effect was rather pronounced in the case of cracks propagating parallel to elongated grains and to lines of primary precipitates. Interaction with microstructural barriers deflected the cracks in shear-controlled extension mode, but did not change the general tendency. |
| Databáze: | OpenAIRE |
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