Characterisation of stress concentration features in the a+ b titanium alloys

 

W.J. Evans, D. Davies and M.T. Whittaker

 

Materials Research Centre, School of Engineering. Swansea University, Singleton Park, Swansea SA2 8PP, UK

w.j.evans@swansea.ac.uk

 

ABSTRACT: The paper explores the impact of texture in the titanium alloy Ti-6-4 on the fatigue response of plain and notched test-pieces. In particular it examines the behaviour of specimens orientated parallel (0 degrees) and perpendicular (90 degrees) to the rolling direction in uni-directionally rolled plate. The measurements clearly demonstrate the importance of basal plane orientation and available basal and prismatic slip systems in determining the observed fatigue lives. For this publication, notch effects are related to a round cylindrical geometry (RCN) with K_t = 1.4. Differences between strain control plain specimens and notches are noted. These are explained through the application of critical strain lifing methods such as Coffin-Manson and Walker. Differences induced by high R values are highlighted.

Keywords: Texture, titanium, notches, prediction

 

RESUMO: Este artigo explora o impacto da textura da liga Ti-6-4 no comportamento à fadiga de provetes lisos e entalhados. Em particular, é examinado o comportamento de provetes com orientação paralela (0o) e perpendicular (90º) àdirecção de laminagem de material laminado unidireccional. As medições demonstram claramente a importância da orientação do plano basal e sistemas de escorregamento disponíveis na vida à fadiga. Para este artigo, efeitos de entalheforam estudados com uma geometria cilíndrica (RCN) com Kt = 1.4. Diferenças entre provetes entalhados e nãoentalhados testados com controlo de deformação são registadas e explicadas pela aplicação de métodos de previsão de vidabaseados na deformação, como Coffin-Manson e Walker. As diferenças resultantes de valores elevados de R sãosublinhadas.

Palavras chave: textura, titânio, entalhes, previsão

 

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References

[1] W.J. Evans, J.P. Jones, and P. Crofts, Titanium 2003 Science and Technology, 3, (2004), 1807.        [ Links ]

[2] W.J. Evans,, R.W. Evans, M. Whittaker, and W. Voice, Titanium 2003 Science and Technology, 3, (2004), 1759.

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[4] W.J. Evans, J.P. Jones, and M.T. Whittaker, Int. Journal of Fatigue, 27, (2005), 1244.

[5] W.J. Evans, “Microstructure and the development of fatigue cracks at notches” Material Science & Engineering A263, (1999), 160.

[6] BS7270, “British standard method for constant amplitude strain controlled fatigue testing”, British Standards Institution

[7] L.F. Coffin, Fatigue at High Temperatures, ASTM STP520, (1973), 744.

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[9] H. Neuber, Transactions, ASME, Journal of Applied Mechanics, (1968), 544.

[10] K. Walker, Effects of Environment and Complex Loading History on Fatigue Life, ASTM STP 462, (1970), 1.