UPPER BOUNDARY CALCULATION OF ISOTHERMAL YIELD OF A RING BLANK

High-strength materials are pressure-treated under isothermal conditions with heating using a hydraulic forging equipment. At the same time, along with strainer- hardening, the workpiece material exhibits viscous properties, i.e. it is viscoplastic. This factor must be taken into account when developing pressing technology, since the power modes of stamping and the maximum possibilities of shaping depend significantly on the speed of the operation. A yield with heating of a ring blank under viscoplastic conditions is viewed. The relations for calculating the force and deformation modes of a ring blank yield under the axial symmetry scheme are proposed. The energy method of balancing the capacities of internal and external forces was used to calculate the power regime. Coulomb's law of friction is adopted on both: tool contact surfaces and the ring blank. The internal force capacities were calculated in the deformation block and on the fracture surfaces of the displacement velocities in accordance with the selected kinematically possible velocity field, including the friction surfaces. The optimization of the velocity field was carried out according to the principle of minimum operating pressure. The assessment of the damage to the material of the blank is carried out according to the energy and deformation criteria of destruction. The calculated results of the yield force and material damage for high-strength aluminum and titanium alloys are presented. It is shown that under isothermal yield of a ring blank, the force decreases at low operating speeds. The damage rate of a number of materials, the behavior of which is described by the energy theory of destruction, decreases with a decrease in the speed of the operation. For materials subject to the deformation theory of fracture, the rate of deformation has no effect on damage, but is determined only by the degree of deformation.

viscoplasticity, power, speed, pressure, material damage