Analytical Expression for Calculating the Average Strain Rate of an Axisymmetric Workpiece during Screw Compression

Abstract

Computer simulation of the screw compression makes it possible to determine the material stress-strain state affecting the microstructure formation and the physical and mechanical properties. One of the important parameters in the simulation is the material average strain rate in the deformation zone. Using this parameter in computer simulation of the screw compression is especially required when employing specialized software packages to study metal forming processes. This determines the objective of the work: to derive an analytical expression that allows for calculation the average strain rate under high-temperature thermomechanical treatment of a structural steel billet under screw compression, depending on the process conditions, namely, taking into account the billet rotational speed, the tilt angle of the forming rolls, and the radius of the calibration part of the rolls. The paper proposes an approach to determining the average strain rate for a cylindrical structural steel billet under screw compression, based on the hypothesis of plane sections. Using the method of multifactorial experimental design, where three technological parameters of the process were varied - the billet rotational speed, the tilt angle of the rolls, and the radius of the roll calibration part - the dependence of the strain rate was evaluated. An analytical expression is proposed describing the billet average strain rate under high-temperature thermomechanical treatment with screw compression as a function of the process conditions, in particular accounting for the billet rotational speed, the tilt angle of the forming rolls, and the radius of the roll calibration part. This analytical expression makes it possible to obtain the required boundary condition for computer simulation of the screw compression for an axisymmetric billet in a specialized software program.