Imperial College London
Alternate

ProfessorFionnDunne

Faculty of Engineering, Department of Materials

Principal Research Fellow
 
 
 
//

Contact

 

+44 (0)20 7594 2884fionn.dunne

 
 
//

Location

 

104Royal School of MinesSouth Kensington Campus

//

Summary

 

Publications

Citation

BibTex format

@article{Zheng:2016:10.1016/j.jmps.2016.08.008,
author = {Zheng, Z and Balint, D and Dunne, F},
doi = {10.1016/j.jmps.2016.08.008},
journal = {Journal of the Mechanics and Physics of Solids},
pages = {411--427},
title = {Dwell fatigue in two Ti alloys: an integrated crystal plasticity and discrete dislocation study},
url = {http://dx.doi.org/10.1016/j.jmps.2016.08.008},
volume = {96},
year = {2016}
}
Download

RIS format (EndNote, RefMan)

TY  - JOUR
AB  - It is a well known and important problem in the aircraft engine industry that alloy Ti-6242 shows a significant reduction in fatigue life, termed dwell debit, if a stress dwell is included in the fatigue cycle, whereas Ti-6246 does not; the mechanistic explanation for the differing dwell debit of these alloys has remained elusive for decades. In this work, crystal plasticity modelling has been utilised to extract the thermal activation energies for pinned dislocation escape for both Ti alloys based on independent experimental data. This then allows the markedly different cold creep responses of the two alloys to be captured accurately and demonstrates why the observed near-identical rate sensitivity under non-dwell loading is entirely consistent with the dwell behaviour. The activation energies determined are then utilised within a recently developed thermally-activated discrete dislocation plasticity model to predict the strain rate sensitivities of the two alloys associated with nano-indentation into basal and prism planes. It is shown that Ti-6242 experiences a strong crystallographic orientation-dependent rate sensitivity while Ti-6246 does not which is shown to agree with recently published independent measurements; the dependence of rate sensitivity on indentation slip plane is also well captured. The thermally-activated discrete dislocation plasticity model shows that the incorporation of a stress dwell in fatigue loading leads to remarkable stress redistribution from soft to hard grains in the classical cold dwell fatigue rogue grain combination in alloy Ti-6242, but that no such load shedding occurs in alloy Ti-6246. The key property controlling the behaviour is the time constant of the thermal activation process relative to that of the loading. This work provides the first mechanistic basis to explain why alloy Ti-6242 shows a dwell debit but Ti-6246 does not.
AU  - Zheng,Z
AU  - Balint,D
AU  - Dunne,F
DO  - 10.1016/j.jmps.2016.08.008
EP  - 427
PY  - 2016///
SN  - 0022-5096
SP  - 411
TI  - Dwell fatigue in two Ti alloys: an integrated crystal plasticity and discrete dislocation study
T2  - Journal of the Mechanics and Physics of Solids
UR  - http://dx.doi.org/10.1016/j.jmps.2016.08.008
UR  - https://www.sciencedirect.com/science/article/pii/S002250961630223X
UR  - http://hdl.handle.net/10044/1/39528
VL  - 96
ER  -
Download