International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

One of the effective ways to control the properties of copper is to refine its structure to a nano- or ultrafine-grained level, and primarily with the help of severe plastic deformation. At the same time, radial-shear rolling is one of the promising methods for obtaining long-length rods with a gradient ultra-fine-grained structure. It is known from a number of scientific works that one of the main factors influencing the possibility of obtaining an ultrafine-grained structure in various ferrous and non-ferrous metals and alloys is the deformation temperature of these metals and alloys. The aim of the work is to study the influence of the deformation temperature at the radial-shear rolling mill on the microstructure evolution of copper. The following deformation temperatures of copper rods were selected for the planned studies: 20°C, 100°C and 200°C. The conducted studies have shown that the implementation of radial-shear rolling at ambient temperature compared with rolling at temperatures of 100°C and 200°C made it possible to achieve more intensive refinement of the initial structure. And first of all, this is due to the fact that with radial-shear rolling of copper, realized at ambient temperature, there are no dynamic return processes.

The work is devoted to experimental studies of the influence of radial shear rolling on the microstructure evolution of the VT-1 titanium alloy and its gradient distribution over the cross section, as well as changes in mechanical properties. In the course of the conducted studies, two different types of microstructure were obtained. At the periphery of the bar near the surface, a relatively equiaxed ultrafine-grained structure with a grain size of 300-600 nm was obtained, while in the axial zone of the bar, an oriented striped texture was obtained. The resulting structure difference of the peripheral and central zones indicates the gradient nature of the structure distribution. This type of distribution is confirmed by the results of the microhardness study over the cross section of a bar rolled to a diameter of 15 mm. The ultimate strength after deformation increased by 58%, while the elongation decreased by 15%.

This work is devoted to the study of the internal defect closure during metal broaching in step-wedge strikers with wedge and depression by FEM in Deform program. A through cylindrical hole with a diameter of 3 mm was considered as an internal defect. At the same time, three variants of the defect vertical location were modeled – in the workpiece center, near the upper face of the wedge and near the lower face of the depression. In all three cases, the internal defect closure is uneven. The most intense defect closure is observed when it is located in the workpiece axial zone. Defects located near the strikers surface zones are not closed well enough. The stress-strain state analysis showed that the defect location affects the distribution nature of stresses and strains along the workpiece section.

A computer simulation of the broaching of the workpiece in step-wedge-shaped strikers of the first and second configurations was carried out by the finite element method. The comparison was made according to the following parameters of the stress-strain state: equivalent strain, average hydrostatic pressure, damage criterion, as well as the deformation force. A comparative analysis of the stress – strain state showed that the second configuration of step-wedge-shaped strikers is the most optimal option for implementing the process of broaching rectangular or square blanks. When using them, a more uniform distribution of the stress state is realized, the deformation processing is sufficiently realized in comparison with the broaching in step-wedge-shaped strikers of the first configuration

The creation and calculation of computer models of various products under load with the properties of UFG materials in the normal and irradiated state was performed. To model the UFG properties of non-irradiated AISI-321 steel, hardening curves were constructed based on the Hall-Petch equation for the base state of the material at a grain size of 1500 nm and for two UFG states (with grain sizes of 700 and 200 nm). To simulate the properties of irradiated AISI-321 steel, plastometric tests were performed using uniaxial compression of cylindrical samples at constant values of the strain rate of 1 s-1 and the temperature of 20°C on the “Gleeble 3800” plastometric unit. Fast neutron fluence with the following values was selected as a variable parameter: 0.5∙1018 n/cm2, 1∙1018 n/cm2, 0.5∙1019 n/cm2, 1∙1019 n/cm2. The maximum operating pressure of 340 MPa was used as a static load. The simulation results showed that for both parts, the use of the material in the UFG state is the most appropriate solution.