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The article, based on the performed theoretical research, solves the essential scientific and technical problem of increasing the accuracy of identification of wave processes in a hydrodynamic system (pipeline) by developing a generalized method of mathematical designing of the dynamics of a continuous viscous and weakly compressed fluid in the hydrodynamic system pipeline based on the Navier-Stokes equation. Amplitude-frequency characteristics represent parameters of wave processes in the hydraulic drive system. A partial solution of Navier–Stokes equations, under zero initial conditions, is proposed in the form of four-pole equations, the components of which are represented in the form of the Laplace image of the corresponding relative pressure and flow coordinates and the the hydraulic line parameters determine the four-pole elements themselves It is also proposed to determine the values of the four-pole elements based on time constants and relative damping coefficients on the frequency characteristics of hydraulic lines with distribution parameters based on the condition of equality of the first resonant frequencies and amplitudes (at these frequencies). With the help of the developed methods, the primary dynamic parameters of the amplitude-frequency characteristics of continuous viscous and weakly compressed liquid in the pipeline of hydraulic systems for different flow ranges. This made it possible to achieve the following practical results: the high degree of adequacy of the developed mathematical model indicates an increase in the reliability of determining the operating characteristics when designing a hydraulic drive. The high accuracy of determining the first resonant frequencies and amplitudes allows for creating a hydraulic pump with improved operational characteristics.

Purpose. Development of highly effective composite diamond-containing materials based on WC‒Co matrices with CrB2 additives with improved mechanical and performance properties for creating matrices of rock-cutting tools for drilling oil and gas wells. Methodology. The assigned tasks were solved using a comprehensive research method, which includes a review and synthesis of literary sources; conducting analytical studies of existing composite diamond-containing materials; scanning electron microscopy (SEM) methods; X-ray phase analysis methods; calculation of experimental data by the Rietveld method, developed for the characterization of crystalline materials by powder X-ray diffraction; the Williamson-Hall technique. Findings. It has been established that the structure of the initial 94 %WC–6 %Co composite consists of WC phases with crystal lattice parameters a = 0.2906, c = 0.2837 nm and graphite with lattice parameters a = 0.2461, c = 0.6708 nm. The addition of chromium diboride to the composition of the 94 %WC–6 %Co sample leads to the decomposition of the CrB2 phase and the formation of the final phase composition: WC + B2CoW2 + Cgraphite + solid solution of tungsten and carbon in cobalt. Originality. It was shown for the first time that if the WC–6Co system is characterized by insignificant solubility of the components in each other, then in the WC–Co–CrB2 system there is a significant mutual dissolution of the components, which leads to a decrease in their sizes during the sintering process. When the threshold concentration (~4 %) of chromium diboride in the charge is reached, phases of the hexagonal WC group and new phases of the orthorhombic group B2CoW2 and amorphous carbon inclusions begin to form in the structure of the composite. Practical value. A highly effective composite diamond-containing material based on WC‒Co matrices with CrB2 additives with increased mechanical (hardness, crack resistance, compressive and bending strength) and operational (wear resistance, productivity) properties has been developed to create a highly effective rock-cutting tool for drilling oil and gas wells. [ABSTRACT FROM AUTHOR]

The article is devoted to improving methods for designing a finite element model of rotor dynamics. For this purpose, numerical implementation of the authors’ computer program “Critical frequencies of the rotor” was developed based on the computer algebra system MathCAD. As a result of the scientific work, a refined mathematical model of rotor dynamics using finite beam elements was created. This model considers the dependence of the radial stiffness characteristics of the bearing supports on the values of the critical frequencies. The reliability of the mathematical model was justified by the permissible differences of the obtained results within 2% compared with the results of finite element analysis using the ANSYS software. The theorem was also proven by the mutual location of the spectra of the natural and critical frequencies. Overall, the proposed scientific approach reduces preparation and machine time compared to numerical modeling using the ANSYS software without losing the accuracy of the calculations.

This article is devoted to developing a mathematical model of nonlinear bearing supports for turbopump units of liquid rocket engines considering initial gaps and axial preloading. In addition to the radial stiffness of the bearing support, this model also considers the stiffness of the bearing cage, the rotational speed of the rotor, axial preloading of the rotor (due to which the inner cage shifts relative to the outer, changing the radial stiffness of the support), as well as radial gaps between contact elements of the bearings. This model makes it possible to calculate the stiffness of the bearing supports more accurately. The proposed model is realized using both the linear regression procedure and artificial neural networks. The model’s reliability is substantiated by the relatively small discrepancy of the obtained evaluation results with the experimental data. As a result, this model will allow determining the critical frequencies of the rotor with greater accuracy. The results have been implemented within the experience of designing turbopump units for State Company “Yuzhnoye Design Office”.

The dependence of the electrochemical characteristics of layered cathode materials LiNixMnyCozO2 (0.4 ≤ x ≤ 0.6; y = 0.2, 0.3; z = 0.2, 0.4) on the method of applying a protective layer of nanoparticles of lithium-conductive material Li1.3Al0.3Ti1.7(PO4)3 with NASICON structure onto their surface has been investigated. It is shown that the surface modification reduces the capacity fading during prolonged charge/discharge cycling (up to 15%) and improves the suitability for fast charge/discharge processes. [ABSTRACT FROM AUTHOR]

The application of materials with a perovskite structure has currently become one of the most promising approaches for the development of photovoltaic systems. A method for high-speed synthesis (under 15 minutes) of CaTiO3 perovskite — TiO2 rutile with the possibility of concurrent doping of the product has been developed. The density of electronic states, phase composition features, and resistivity of niobium-doped perovskite (CaTiO3 ) were investigated. The calculations of the density of electronic states for niobium-doped CaTiO3 have shown that at low concentrations of niobium, the samples exhibit conductivity characteristic of semiconductors. Since niobium has one more valence electron compared to titanium, as the niobium content increases, the Fermi level shifts to the band of free states. This shift of the Fermi level should lead to a change in the nature of the conductivity of doped crystals, eventually transitioning to metallic conductivity at high concentrations of niobium. Composite analysis (CaTiO3 + ТіО2 ) by X-ray diffraction has shown that the use of niobium as a doping element significantly accelerates the CaTiO3 synthesis reaction, and increases the perovskite concentration in the sample. The concentration of CaTiO3 in the sample the with niobium is 83% vol. at a temperature of 900 ºC and a synthesis time of 5 min, whereas when using a mixture without Nb, the content of perovskite will be only 58% vol. at a synthesis time of 12 min. X-ray phase analysis methods confirm the formation of a solid solution (doping) Ca (Ti,Nb)O3, resulting in the preparation of samples (CaTiO3 + ТіО2 ) with resistivity inherent to semiconductors. [ABSTRACT FROM AUTHOR]

Purpose. Development of a methodology for optimizing the technological parameters of the airlift operation, based on the analysis of the pressure balance in the annulus and in the drill string that occurs during drilling. Methodology. The tasks were solved by a complex research method, which includes a review and generalization of literary and patent sources, analytical studies on existing methods for optimizing the technological parameters of drilling with reverse circulation using an airlift. Findings. It has been established that in the study on the airlift circulation method during rotary drilling with reverse circulation, an important role is played by the analysis of the pressure balance arising in the course of drilling in the annulus and in the drill string. It takes into account both hydrostatic pressures and pressure losses for pumping water and water-air mixture. A technique has been developed for assessing the effect of rate of penetration on circulation parameters. Originality. For the first time, it has been shown that the analysis of the pressure balance makes it possible to establish, with a given accuracy, the average effective values of the output parameters: the density of the water-air mixture, its upward flow rate, and the air flow rate at a given velocity of the upward flow of water as it approaches the mixer. Practical value. The proposed technique makes it possible to establish the dependence of the values of the output parameters on the depth of the well, as well as the required compressor performance to provide a given drilling fluid flow rate. [ABSTRACT FROM AUTHOR]