Moscow Polytechnic University, Moscow, Russia

Yu. K. Filippov, Dr. Eng., Prof ., Dept. of Materials Forming and Additive Technologies, e-mail: yulianf@mail.ru
D. A. Gnevashev, Cand. Eng., Head of the Dept. of Materials Forming and Additive Technologies, e-mail: dengnevashev@mail.ru
Le Chung Zung, Postgraduate Student, Dept. of Materials Forming and Additive Technologies

The dependence of the construction of the hardening curve under uniaxial compression between the measurements of the deformed metal and the stress intensity during plastic deformation is investigated and established. Graphs of the dependence of the deformation value on the stress value for steel 20 GOST 1050-2013 are constructed, thereby making it possible to predict the properties of parts obtained by cold forging. In order to construct the dependence of the strain intensity and stress intensity and to plot the hardening graph, experiments were carried out on compressing samples from the researched metal. Due to good lubrication at the ends of the sample (periodically replaced gaskets made of polyethylene film in combination with engine oil), the stress state can be considered linear. The stress state index K = 0,33, the Lode-Nadai indicator μ_σ = 1. To reduce the barrel shape during upsetting, the height of the samples and the diameter of the initial dimensions are within the limits 2 ≥ H₀/D₀ ≥ 1. Steel 20 GOST 1050-2013 was selected for the study. Hot-rolled round steel rolled according to GOST 2590-88 was used as blanks. To determine stresses at different degrees of deformation, it is possible to use an approximate mathematical expression, since the use of a graph is not always convenient and does not provide high accuracy. To obtain a mathematical expression, an approximation of the hardening curve was carried out in the Excel program. Excel has a polynomial function with a confidence value of 0.9931, for use in modeling in the QForm software package.

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