Том 29, № 1 (2019)

Introduction. The classical topology optimization leads to a prediction of the structural type and overall layout, and gives a rough description of the shape of the outer as well as inner boundaries of the structure. However, the probabilistic topology optimization (or reliability-based topology optimization) model leads to several reliability-based topologies with high performance levels. The objective of this work is to provide an efficient tool to integrate the reliability-based topology optimization model into free vibrated structure.
Materials and Methods. The developed tool is called inverse optimum safety method. When dealing with modal analysis, the choice of optimization domain is highly important in order to be able to eliminate material taking account of the constraints of fabrication and without affecting the structure function. This way the randomness can be applied on certain boundary parameters.
Results. Numerical applications on free vibrated structures are presented to show the efficiency of the developed strategy. When considering a required reliability level, the resulting topology represents a different topology relative to the deterministic resulting one.
Discussion and Conclusion. In addition to its simplified implementation, the developed inverse optimum safety factor strategy can be considered as a generative tool to provide the designer with several solutions for free vibrated structures with different performance levels.

Introduction. The article presents a simplest differential game with four participants. The players move on a plane and can do simple movements. The game under considering comes down to a cooperative differential game. The dynamic stability of such optimality principles as the S-kernel and Shapley vector is shown.
Materials and Methods. The standard procedures of the cooperative game theory are applied to the analysis and decision of a cooperative differential game. The conditional and optimum trajectories, along which the players move, are found using the Pontryagin’s maximum principle. When constructing the characteristic function, the minimax approach is used.
Results. The optimum strategy of the players, conditional and optimum trajectories of their movements at various ways of formation of coalitions are written out explicitly. The characteristic function is constructed according to the accepted max-min principle; the S-kernel and Shapley vector are considered as a decision. The components of the Shapley vector are written out explicitly; the fact that the Shapley vector is an element of the S-kernel and nonemptiness of the S-kernel, when the players are moving along an optimum trajectory, are shown. Using the results of the static cooperative game theory for researching differential games, we face the problems, which are connected with specifics of the differential equations of the movement. As a priority, the problem of the dynamic stability of the optimality principles under consideration is identified. In the work, the dynamic stability of the Shapley vector and S-kernel is shown.
Discussion and Conclusion. The results of the research show that the analysis of the dynamic stability of the optimality principles considered is relevant.

Introduction. The aim of the work is to develop a mathematical model of a part based on a parametric model of graphic systems.
Material and Methods. The review of the status of the question of developing a mathematical model of a part based on graphic systems showed the possibility of controlling the geometric shape of a part through the variables of a parameterized drawing. A proposal was made to use design parameterization in the calculation of the parameters of technological processes in computer-aided design systems.
Results. The article establishes links between the design parameters of the part drawing and tabular values of the variables. The revealed relationships between the parameters in the drawing and the variables in the table make it possible to change the geometric shape of the part by changing the values in the variable table, i.e. the drawing is managed through the table. It is proposed to use this system of work with the parametric drawing in computer-aided design systems for calculating the parameters of technological processes.
Discussion and Conclusion. The tasks solved in this article allow making a step in increasing the level of automation of parameter calculations in computer-aided design systems. The implementation of the developed methodology for constructing mathematical models of parts based on graphic systems will increase the overall level of automation of developing geometric drawings of parts. The implementation of this technique in computer-aided design systems allows automating the calculation of parameters (cutting modes, time norms, technological dimensions on transitions, etc.).

Introduction. Current practices to prepare potatoes for sale have significant drawbacks. The aerodynamic method of potato treatment eliminates them owing to its design features. IEEP – branch of FSAC VIM has manufactured an experimental model of the installation POKAS-1 IEEP to test this method. The required power, energy inputs and productivity of the installation were determined and optimized with the aim to achieve highly efficient treatment of potato tubers.
Materials and Methods. Various operating modes of the installation were studied in the experiments according to the developed program and methodology with the use of theoretical modeling methods based on the insight of the processes occurring during the potato treatment.
Results. The experimental studies revealed the patterns how the required power, productivity and energy intensity of potato treatment process varied with the nozzle outlet air temperature. The empirical relationship was found to determine the mass of soil particles removed from the potato surface depending on the air temperature.
Discussion and Сonclusion. The most efficient pre-sale potato treatment by the aerodynamic method was found at the drum rotation frequency of 20 min–1 and the nozzle output temperature of 40 °C, with the optimal required power of the installation being 5.68 kW. When the installation productivity increased from 0.025 t/h to 0.030 t/h, the energy intensity of the technological process was also going up; with the further increase in the productivity from 0.030 t/h to 0.036 t/h the energy intensity of the process dropped drastically. The energy intensity of the process varied from 794.5 to 1124.3 MJ/t depending upon the temperature regime and high power consumption of the installation. The developed method allowed calculating the required power and productivity of the aerodynamic installation and the energy inputs for the process under consideration.

Introduction. Modern manufacturing technologies of powder materials allow obtaining particles sized 0.1–0.5 μm. Powders with such dispersion have a very high surface energy and, consequently, unique properties. Powders with a given size can be used as an additive to motor oil to form the surface film with high tribological properties. However, the widespread use of ultra-nanoscale powder materials as additives to motor oil limits sedimentation and aggregation of the particles. As a result, the dimensions of the metal crystals increase to dozens of microns and their particles are then retained by oil filters of engines that leads to efficiency decrease and even to clogging oil-conducting channels and to setting the friction surfaces of the parts. The most technically competent solution for increasing sedimentation resistance of the lubricant composition is the use of chemical stabilizers forming the thinnest film at the surface of metal particles, which not only hinders particle aggregation.
Materials and Methods. As stabilizers of dispersed metal powders in lubricant compositions, organic compounds of various classes are used. The analysis of several stabilizers of disperse metal powders is given in the paper and new compositions are proposed: apinezon MN, polyethylene glycol sebacate and commodity stabilizer apiezon L. The methods of stabilizers synthesis and examination of their activity are described.

Results. The stabilization activity of the developed preparations was compared to the basic version: oleic acid. Addition of the ester of ethylene glycol sebacate had no stabilizing effect on the lubricant composition. The synthesized MN and Mg reagent apeizon L show stabilizing properties with respect to metallic powders of the lubricant composition, comparable with the properties of oleic acid.

Discussion and Conclusion. Since apiezon greases are a mixture of hydrocarbons, their corrosivity is much lower than that of oleic acid, they can be recommended for practical use.