PSI - Issue 18

Tretyakov M.P. et al. / Procedia Structural Integrity 18 (2019) 816–822 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Conclusions A technique of carrying out rheological tests of structural steels at the postcritical deformation stage at high temperatures under tensile conditions with the possibility of registering changes in the geometry of the working part of the samples during testing has been developed. The temperature regimes and test speeds were determined, and the sequence of loading and holding the samples in accordance with the objectives of the study was chosen. Experimental diagrams of deformation of the samples of the investigated steel at a temperature of 400 °С, 500 °С and 600 °С at exposures with fixed deformation at various stages of elastoplastic and postcritical deformation were built. Experimental data obtained in the course of the project implementation show that when a steel is stretched X15CrNi12-2 at the postcritical deformation stage at high temperatures, rheological processes actively occur. This is confirmed by the dependence of the recorded loading patterns on the test speed and the observed relaxation processes at exposures with a fixed elongation of the samples. The relaxation processes in the samples of the examined steel at the postcritical stage of deformation substantially depend on the test temperature and the degree of elongation achieved by the time of exposure. An increase in temperature leads to a more intensive decrease in the relative load at exposures, and an increase in the degree of postcritical deformation leads to an increase in the intensity of relaxation processes, and this effect is most pronounced with increasing temperature. The revealed experimental dependences confirm the need to take into account the rheological component of the mechanical behavior of steels when studying postcritical behavior at high temperatures. Acknowledgements The work was carried out with support of the Russian Science Foundation (Project 18-79-00216) in the Perm National Research Polytechnic University. References Vildeman, V.E., Sokolkin, Yu.V., Tashkinov, А.А., 1997. Mechanics of inelastic deformation and fracture of composite materials, Moscow, Nauka. pp. 288. Vildeman, V.E., 2008. Mechanics of postcritical deformation and questions of strength analysis methodology, International Journal for Computational Civil and Structural Engineering 4 (2), 43. Vildemann V.E., Tretyakov M.P., 2013. Analysis of the effect of loading system rigidity on postcritical material strain. Journal of Machinery Manufacture and Reliability (3), 219-226. Vildeman, V.E., Lomakin, E.V., Tretyakova, T.V., Tretyakov, M.P, 2016. Development of inhomogeneous fields under postcritical deformation of steel specimens in extension, Mechanics of Solids 51(5), 612-618. Tretyakov, M.P., Wildemann, V.E., Lomakin, E.V., 2016. Failure of materials on the postcritical deformation stage at different types of the stress strain state, Procedia Structural Integrity 2, 3721-3726. Tretyakov, M.P., Tretyakova, T.V., Wildemann, V.E., 2018. Regularities of mechanical behavior of steel 40Cr during the postcritical deformation of specimens in condition of necking effect at tension. Frattura ed Integrità Strutturale 43, 145-153. Wildemann V.E., Lomakin E.V., Tretyakov M.P., 2014. Postcritical deformation of steels in plane stress state. Mechanics of Solids 49 (1), 18-26. Wildemann V.E., Tretyakov M.P., 2019. Experimental study of postcritical deformation and failure of steels at high temperature. PNRPU Mechanics Bulletin 1, 27-37. Lokoshchenko A.M., 2016. Use of a vector damage parameter in modeling of long-term strength of metals. Mechanics of Solids 51 (3), 315-320. Agahi K.A., Basalov Y.G., Kuznetsov V.N., Fomin L.V., 2009. Modeling of creep process with accounting the pre-failure stage and identification of the model. Vestnik Sam. GTU. Series: Physical and mathematical sciences 2 (19), 243-247. Radchenko V.P., Saushkin M.N., Goludin E.P., 2012. Stochastic model of non-isothermal creep and long-term strength. App. Mech. and Tech. Phys. 53 (2), 167-174. Namestnikova V.I., 1985. Long-term strength of a rod with a circular recess. Deformation and destruction of solids, 78-83. Shesterikov S.A., Lokoschenko A.M., 1996. Effect of stress concentration on long-term strength. Problems of Strength 5, 32-35.