An experimental and analytical study of a titanium alloy cold creep in the pure bending conditions

• Main Authors: Vladimir I. Nigmatullin, Oksana G. Rybakina, Olga A. Strogonova
• Format: Article
• Language: English
• Published: Krylov State Research Centre 2019-08-01
• Series: Труды Крыловского государственного научного центра
• Subjects: deepwater submersibles; cold creep; titanium alloy; strain; tension; bending
• Online Access: https://transactions-ksrc.ru/eng/archive/An-experimental-and-analytical-study-of-a-titanium-alloy-cold-creep-in-the-pure-bending-conditions/

Object and purpose of research. This paper studies pure bending of titanium alloy strap with different properties in tension and compression under cold creep conditions. The effect of opposite-sign plastic strain on subsequent creep process is studied both analytically and experimentally. Materials and methods. Creep is described with the previously method based on the tests of samples performed at constant total strain rate in a wide range (5 orders of magnitude). The experiment was performed at Instron 8800-series test machines. Main results. Titanium alloy strap was subjected to pure bending. The bending moment and tension-compression strains on its surfaces were recorded. These data made it possible to obtain stress-strain diagrams for this material that coincided with the diagrams obtained independently for uniaxial tension and uniaxial compression. Analytical and experimental studies were performed in cold-creep conditions. Stress and strain distributions in the strap thickness were calculated for each moment of time. It has been shown that the creep is accompanied by stress redistribution in the strap thickness: the stresses near the surfaces relax, as a result the creep decelerates. The effect of pre-bending on subsequent creep of the strap turned upside down has also studied: it turned out that the creep strains in this case are greater than for the alloy in the initial state (this phenomenon is similar to Bauschinger effect). Conclusion. These results will enable structural calculations of titanium-alloy deepwater submersibles taking cold creep into account.