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Understanding thermal alleviation in cold dwell fatigue in titanium alloys

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Title: Understanding thermal alleviation in cold dwell fatigue in titanium alloys
Authors: Zheng, Z
Stapleton, A
Fox, K
Dunne, F
Item Type: Journal Article
Abstract: Dwell fatigue facet nucleation has been investigated in isothermal rig disc spin tests and under anisothermal in-service engine conditions in titanium alloy IMI834 using α-HCP homogenised and faithful α-β lamellar microstructure crystal plasticity representations. The empirically observed facet nucleation and disc failure at low stress in the isothermal spin tests has been explained and originates from the material rate sensitivity giving rise to soft grain creep accumulation and hard grain basal stresses which increase with fatigue cycling until facet nucleation. The α-HCP homogenised model is not able to capture this observed behaviour at sensible applied stresses. In contrast to the isothermal spin tests, anisothermal in-service disc loading conditions generate soft grain slip accumulation predominantly in the first loading cycle after which no further load shedding nor soft grain creep accumulation is observed, such that the behaviour is stable, with no further increase in hard grain basal stress so that facet nucleation does not occur, as observed empirically. The thermal alleviation, which derives from in-service loading conditions and gives the insensitivity to dwell fatigue dependent on the temperature excursions, has been explained. A stress-temperature map for IMI834 alloy has been established to demarcate the ranges for which the propensity for dwell fatigue facet nucleation is high, threatening or low.
Issue Date: 1-Dec-2018
Date of Acceptance: 25-Jul-2018
URI: http://hdl.handle.net/10044/1/62889
DOI: 10.1016/j.ijplas.2018.07.018
ISSN: 0749-6419
Publisher: Elsevier
Start Page: 234
End Page: 252
Journal / Book Title: International Journal of Plasticity
Volume: 111
Issue: 1
Copyright Statement: © 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/)
Sponsor/Funder: Engineering & Physical Science Research Council (EPSRC)
EPSRC
Engineering & Physical Science Research Council (E
Funder's Grant Number: EP/K034332/1
EP/K034332/1
138874
Keywords: Science & Technology
Technology
Engineering, Mechanical
Materials Science, Multidisciplinary
Mechanics
Engineering
Materials Science
Cold dwell fatigue
Crystal plasticity
Titanium alloys
Microstructure
Temperature sensitivity
Aero-engine discs
Thermal alleviation
CRYSTAL PLASTICITY FE
CRACK NUCLEATION MODEL
SENSITIVE FATIGUE
HIGH-TEMPERATURE
DEFORMATION-BEHAVIOR
SLIP TRANSFER
TI ALLOYS
MICROSTRUCTURE
TI-6242
SIMULATIONS
Mechanical Engineering & Transports
0905 Civil Engineering
0912 Materials Engineering
0913 Mechanical Engineering
Publication Status: Published
Online Publication Date: 2018-07-26
Appears in Collections:Materials
Faculty of Engineering