TRANSACTIONS OF THE KRYLOV STATE RESEARCH CENTRE

Science journal

 
ISSN (print) 2542-2324 /(online) 2618-8244


Articles of The Transactions of KSRC








Effect of stress state type and loading history on titanium alloy cold creep



Full text article ( in russian)

Year

 
2018

Issue

 
385

Volume

 
3

Pages

 
50-60

Caption

 
Effect of stress state type and loading history on titanium alloy cold creep

Authors

 
Mikhailov E.Yu., Nigmatullin V.I., Rybakina O.G.

Keywords

 
creep, type of stress state, loading time history, load release

DOI

 
10.24937/2542-2324-2018-3-385-50-60

Summary

 
Object and purpose of research.The paper investigates how preliminary direct or reverse plastic strains influence on the titanium alloy creep properties. The alloy creep behavior under uniaxial tension and compression is compared.
Subject matter and methodsThe material creep behavior is described using a method suggested earlier. It is based on specimen testing under constant rate of the total strain in a wide range of aforementioned strain rate (5 orders of magnitude). The hardening theory used relates stress, residual strain and residual strain rate (in particular case creep strain). The experiments were performed on Instron-8800 test machines.
Main resultsIt is shown that creep parameters of the alloy and corresponding creep curves significantly depend on the stress sign. The calculations well predict the experimental values of the creep strain rate. The effect of the preliminary plastic strain significantly depends on the sign of strain. In case the preliminary residual and the creep strain are opposite in sign, the creep is considerably enhanced (it is analogous to Bauschinger effect). In order to describe this phenomenon, parameters of the material after plastic strain, different from the parameters of the virgin material, are obtained. The occurrence of the creep effect under slow load release, that is related to the applicability of the Gerstner law, is studied.
Conclusion.A method suggested earlier for describing the titanium alloy time-dependent response under climatic temperatures is used in this study with reference to material subjected to preliminary strain and in case of loading sign change. Experimental creep curves are in good agreement with calculations.

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