Об испытании сплошных цилиндрических образцов при растяжении с кручением

Abstract

One of the features of the rheological behavior of metals and alloys at high temperature is their sensitivity to the rate of deformation. This paper proposes a method for studying the dependence between stresses and strain rates based on experimental data for solid cylinder specimen deformed in tension with torsion under non-proportional deformation (complex loading). A strain trajectories with two straight lines is considered. The deformation process is described by two components of the strain rate tensor (axial and shear) in the form of functions of time. At each time, we record the axial force and torque corresponding to them. The function of the force parameters (axial force and torque) recorded in the experiment and the preset kinematic parameters (the rate of tension and the torsional velocity), the strain rate sensitivity coefficient, the strain hardening exponent and the approach angle between the stress vectors and the strain rate on the specimen surface under non-proportional deformation is obtained. The paper also considers particular cases of deformation trajectories of the double-link type, when the second link is uniaxial tension, pure torsion or tension combined with torsion. Analytic formulas for calculating the stress vector and its components, and the approach angle that characterizes the direction of the stress vector in relation to the strain rate vector for points on the specimen cylindrical surface are derived. The method proposed is a generalization of the experimental procedure for plotting shear diagrams from the torsion test data for a material sensitive to the rate and level of strains, based on the Fields Backofen equation. The proposed method was used in processing experimental data obtained after testing the Ti-6Al-4V titanium alloy under non-proportional deformation in tension with torsion under conditions of superplasticity. When processing the test data, the compliance of the “specimen – testing machine” system was taken into account.