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Finite Element Modeling of Hot Compression Testing of Titanium Alloys

Published version
Peer-reviewed

Type

Article

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Authors

Mishra, Sumeet 
Daniel, Christopher S 
da Fonseca, Joao Quinta 

Abstract

This paper presents experimental results and finite element analysis of hot upsetting of titanium alloys Ti64 and Ti407 using a dilatometer in loading mode. All samples showed barrelling, as a consequence of an inhomogeneous temperature distribution and friction. The FE analysis is a full thermomechanical model of the test calibrated using multiple thermocouples. At each nominal temperature and strain-rate, the true flow stress-strain response is inferred using the difference between the initially assumed constitutive response input to the FE analysis, 𝜎𝜎 = 𝑓𝑓(𝑇𝑇, 𝜀𝜀˙, 𝜀𝜀), and the predicted response of the model. The analysis applies new procedures for: (i) modelling the thermal gradient; (ii) finding the flow stress correction due to the inhomogeneity, using literature data as the input to the FE analysis; (iii) smoothing the constitutive data, fitting empirical 𝜎𝜎 = 𝑓𝑓(𝑇𝑇, 𝜀𝜀˙) surfaces at multiple discrete strains. The extracted true constitutive data confirms the moderate strain-softening behaviour in Ti64 alloy, and the FE model predicts the distribution of local deformation conditions, for application in interpretation of microstructure and texture evolution. This highlights the difference between nominal and actual test conditions, showing that the discrepancy varies systematically with test conditions, with the central strain and strain-rate being magnified significantly, by factors of order 2–3.

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Keywords

Journal Title

Journal of Materials Engineering and Performance

Conference Name

Journal ISSN

1059-9495
1544-1024

Volume Title

Publisher

Springer Science and Business Media LLC
Sponsorship
Engineering and Physical Sciences Research Council (EP/R001715/1)