Tula State University, Tula, Russia:

A. V. Chernyaev, Professor at the Department of Mechanics of Plastic Forming (MPF), e-mail: sovet01tsu@rambler.ru
N. A. Usenko, Professor at the Department of MPF
V. A. Korotkov, Senior Researcher at the Department of MPF
V. I. Platonov, Associate Professor at the Department of MPF

This paper examines how to enhance the efficiency of research into uniaxial tensile deformation of material at high temperature in order to establish a relationship between the intensity of stresses and the deformation degree and rate using the case study of an aluminium alloy. As part of comprehensive experimental research, flat specimens are heated to the required temperature and stretched. To achieve this, actuators have to move at different rates, which makes it a labour-intensive process. To enhance the efficiency of experimental research, the authors propose a technique for stretching one flat specimen in a given temperature regime. During the entire stretching period, a cyclic speed change was applied after every 2–3 mm of the grip’s travel. The changing rates of deformation entailed stepwise changes in the acting forces, and a bar ‘load-travel’ graph was built. After the uniaxial tension test was completed, the bars in the graph were connected with smooth lines producing a few curves in one graph. The stepwise change of speed during the tension testing of one specimen in given temperature regime helps establish a relationship between the intensity of stresses and the strain intensity at different deformation rates. The proposed testing technique helps significantly reduce the number of specimens used, reduce the time required for experimental research, and eliminate possible errors in research results caused by heating inaccuracies as it is quite difficult to ensure identical temperatures when conducting separate tests with several specimens.

1. Yakovlev S. P., Chudin V. N., Yakovlev S. S., Sobolev Ya. A. Isothermal deformation of high-strength anisotropic materials. Moscow, Tula : Mashinostroenie-1; Izdatelstvo TulGU, 2003. 427 p.
2. V. P. Golub, A. V. Zheldubovskiy. Technique for testing the tension strength of materials. USSR Certificate of Authorship. No. 1826022. Bulletin No. 15.
3. V. A. Korotkov, V. A. Lazarev, S. N. Larin, V. I. Platonov. Testing method of samples from material under stressing with high temperature. Patent RF, No. 2644452. Applied: 26.12.2016. Published: 12.02.2018. Bulletin No. 5.
4. Loginov Y. N., Golovnin M. A. Technique of determining the parameters of rapid strengthening of an aluminum alloy during hot rolling. Russian metallurgy (Metally). 2017. Vol. 2017, Iss. 3. pp. 188–192.
5. Figlin S. Z., Boytsov V. V., Kalpin Yu. G., Kaplin Yu. I. Isothermal deformation of metals. Moscow : Mashinostroenie, 1978. 239 p.
6. Ogorodnikov V. A. Deformability analysis in metal forming. Kiev : Vishcha shkola, 1983. 175 p.
7. Tretiakov A. V., Zyuzin V. I. Mechanical properties of metals and alloys under forming. Moscow : Metallurgiya, 1973. 224 p.
8. Bo Song, Brett Sanborn. Relationship of compressive stress-strain response of engineering materials obtained at constant engineering and true strain rates. International Journal of Impact Engineering. 2018. Vol. 119. pp. 40–44.
9. Huamiao Wang, Peidong Wu, Srihari Kurukuri, Michael J. Worswick, Yinghong Peng, Ding Tang, Dayong Li. Strain rate sensitivities of deformation mechanisms in magnesium alloys. International Journal of Plasticity. 2018. Vol. 107. pp. 207–222.

10. Yang L. W., Wang C. Y., Monclús M. A., Lu L., Molina-Aldareguía J. M., Llorca J. Influence of temperature on the strain rate sensitivity and deformation mechanisms of nanotwinned Cu. Scripta Materialia. 2018. Vol. 154. pp. 54–59.
11. Hajime Iwasaki, Ryoichi Kariya, Mamoru Mabuchi, Tutomu Tagata, Kenji Higashi. Effects of Temperature and Strain Rate on Elongation at Elevated Temperature in Al – 4.5 Mg Alloy. Materials transactions. 2001. Vol. 42, Iss. 8. pp. 1771–1776.
12. Calle M. A. G., Mazzariol L. M., Alves M. Strain rate sensitivity assessment of metallic materials by mechanical indentation tests. Materials Science and Engineering: A. 2018. Vol. 725. pp. 274–282.
13. Kangkang Wang, Libin Zhao, Haiming Hong, Jianyu Zhang. A strain-ratedependent damage model for evaluating the low velocity impact induced damage of composite laminates. Composite Structures. 2018. Vol. 201. pp. 995–1003.
14. GOST 9651–84 (ISO 783–89). Metals. Methods of tension tests at elevated temperatures (incl. Revision 1). Introduced: 01.01.1986.