| Autor: |
Joseph, Sudha, Joseph, Kavitha, Lindley, Trevor C, Dye, David |
| Rok vydání: |
2019 |
| Předmět: |
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| Zdroj: |
Int. J. Plasticity, 102743, 2020 |
| Druh dokumentu: |
Working Paper |
| DOI: |
10.1016/j.ijplas.2020.102743 |
| Popis: |
The dislocation structures appearing in highly mis-oriented soft/hard grain pairs in near-alpha titanium alloy Ti6242Si were examined with and without the application of load holds (dwell) during fatigue. Dislocation pile-up in a soft grain resulted in internal stresses in an adjacent hard grain which could be relaxed by dislocation multiplication at localized Frank-Read sources, a process assisted by the provision of a relaxation time during a load hold. The rate of this process is suggested to be controlled by pyramidal cross-slip and basal junction formation. A high density of prism pile-ups is observed by dual slip, together with the nucleation of edge dislocations in the soft grain of a highly mis-oriented grain pair, increasing the possibility of cracking. The stress concentration developed by such pile-ups is found to be higher in dwell fatigue (single-ended pile-ups) than in LCF (double ended). Analytical modelling shows that the maximum normal stress produced on the hard grain in dwell fatigue by this pile-up would be near-basal, ~2.5 degree to (0002). This provides support for the dominant hypothesis for the rationalisation of dwell fatigue crack nucleation in Ti alloys, which derives from the Stroh pile-up model, and elaboration of the underlying dislocation phenomena that result from load shedding and lead to basal faceting.
Comment: Author accepted manuscript with Int J Plasticity |
| Databáze: |
arXiv |
| Externí odkaz: |
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