Discrete breathers (DBs) have been described among pure metals with face-centered cubic (FCC) and body-centered cubic (BCC) lattice, but for hexagonal close-packed (HCP) metals, their properties are...

A practical approach to the search for (quasi-) discrete breathers (DBs) in a triangular $\beta$-FPUT lattice (after Fermi, Pasta, Ulam, and Tsingou) is proposed. DBs are obtained by superimposing localizing functions on delocalized nonlinear vibrational modes (DNVMs) having frequencies above the phonon spectrum of the lattice. Zero-dimensional and one-dimensional DBs are obtained. The former ones are localized in both spatial dimensions, and the latter ones are only in one dimension. Among the one-dimensional DBs, two families are considered: the first is based on the DNVMs of a triangular lattice, and the second is based on the DNVMs of a chain. We speculate that our systematic approach on the triangular $\beta$-FPUT lattice reveals all possible types of spatially localized oscillations with frequencies bifurcating from the upper edge of the phonon band as all DNVMs with frequencies above the phonon band are analyzed.

This paper presents the calculations and construction of load diagrams and the static characteristics of individual mechanisms of a mining roadheader, which form a multimotor electric drive system, using the methods of equivalent forces and reduced moments. The productivity of the mine and the roadheader are calculated. The operating forces of idle and on-load mechanisms are calculated, and operation time intervals and a complete working cycle are determined. The load diagrams of mechanisms are constructed and their kinematic diagrams are designed. Based on the calculations performed, asynchronous motors with a short-circuit rotor, which have the closest power values and are suitable in terms of voltage and mode of operation, were selected from the catalogue. The gear reduction ratio is calculated, static resistance moments, and operation speeds to the motor shaft are specified. The static characteristics of the most powerful electric motor of a mining roadheader – or cutter – are formulated. The high accuracy of the calculations was confirmed by computer simulation, which showed minimum errors.

The article studies static and dynamic characteristics of a DC motor with independent excitation by mathematical modeling in MatLab environment for the possibility of further construction of models of electric drive systems with this engine type. A brief theory describing the basic principles of calculating the electric and mechanical parts of a DC motor is presented. A basic structural diagram of a DC motor having an input effect, a transfer function and an output signal is constructed. Particular cases of structural schemes with a permanent and variable magnetic flux of the winding of the excitation and with variable anchor resistance are given. According to the above structural diagrams, a mathematical model of the DC motor in MatLab/Simulink is compiled. The results of modeling a constant-current motor for direct starting with a constant and variable magnetic flux of the excitation winding are obtained. Using the special function ltiview, the frequency characteristics for the main transfer function of the motor are obtained. Modeling of start-up modes at idle and under load was performed. A conclusion was made about the advisability of using direct-current motors in electric drive systems and the importance of the studies carried out for the further modeling of electric drive systems and real mechanisms.

High-density electric current pulses increase the plasticity and reduce the yield stress of metals with negligible heat generation. This effect has great potential for the development of energy-saving technologies for processing hard-to-deform metallic materials. Despite the long history of the study of electroplasticity, there is still no consensus on the physical nature of this effect. In this paper, the effect of repetitive pulses applied at the same or gradually increasing tensile stress on the plastic deformation of copper wire is investigated using a home-made experimental setup. The electroplasticity of the wire in the delivery state and after annealing is compared. It is shown that for a constant tensile stress, the incremental plastic deformation of the wire decreases with each successive pulse. This effect is stronger for annealed wires because they have a lower dislocation density and therefore a lower plasticity resource. The Joule heat release in the specimen and the heating due to plastic deformation are evaluated. The results obtained will be used to fit the parameters of the atomistic model being developed to describe the interaction of electron flow with dislocations.