FGAOU VO "Ural Federal University named after the first President of Russia B. N. Yeltsin", Yekaterinburg, Russia

Yu. N. Loginov, Professor of the Chair for Metal Deformation Processes, e-mail: j.n.loginov@urfu.ru
E. G. Polishchuk, Associate Professor
Yu. V. Tugbaev, Post-Graduate Student of the Department of the Chair for Metal Deformation Processes

The approach to the analysis of the pressing process of metals with a hexagonal close-packed lattice, for example, zirconium, is described. It is noted that in the deformation processes a preferential orientation of the crystals may arise which brings about the properties anisotropy in all directions. During pressing the anisotropy formation occurs under the action of stresses resulting in the plastic deformation. The aim of the paper is to determine the strain tensor components during pressing to predict the properties anisotropy origination for zirconium and similar materials during the pressing process. It is noted that the compression deformation in the radial direction during pressing leads to the radial texture origination and the increase in the Kearns factors in the radial direction. In the tube shaping operations, generalized indices are used to estimate the magnitude of deformation in the radial and tangential directions. To control the Kearns factors, it is necessary to change the relationship between the deformation logarithmic indices during pressing. The deformation zone scheme during the tube pressing has been considered. The plastic zone is located between two hard regions in a spherical coordinate system. The deformation rates field has been described in the form of the corresponding formulas. It is noted that, in accordance with the solution, the deformation rate tensor components are functions of the coordinates. Their integration leads to the determination of the strain tensor components which are also functions of the coordinates that does not allow to describe the deformed state using the constants. The solution of the pressing task and the shear strain rate distribution as an invariant quantity, as well as the strain rate tensor components in a cylindrical coordinate system, are obtained by the finite element method (FEM). It was found that the values of the strain components obtained by the FEM differ significantly from the hypothetical values determined from the deformation zone geometric parameters. It was established that the previously made assumptions in the field of the deformations distribution influencing the texture formation in zirconium and similar alloys with the use of Kearns factors, require the more precise definition. When pressing hollow blanks, it is necessary to take into account the specificity of the metal plastic flow, but not only the relationship between the geometrical parameters of the workpiece and the finished article. To approximate the pattern of the deformed state to the real one, it is necessary to use computational methods that enable to evaluate the strain tensor components.
The work was carried out with partial financial support of the Resolution No. 211 of the Government of the Russian Federation, Contract No. 02.A03.21.0006.

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