Ukrainian Journal of Mechanical Engineering and Materials Science

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Author: search.filters.author.Kuzio, IhorHas files: Yes

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    Simulation modelling of dynamic processes due discontinuous frictional treatment of the flat surfaces
    (Lviv Politechnic Publishing House, 2020) Gurey, Volodymyr; Korendiy, Vitaliy; Kuzio, Ihor; Lviv Polytechnic National University
    Friction treatment refers to surface strengthening (hardening) methods using highly concentrated energy sources. In the course of this processing in the surface layers of the processed surfaces of parts the strengthened layer with nanocrystalline structure is formed. The formed layer has specific physical, mechanical, chemical properties, as well as improved performance properties, which are significantly different from the base metal. A highly concentrated energy source is formed in the contact area of the tool-part due to the high-speed friction (60–90 m/s) of the tool on the treatment surface. Frictional treatment of flat parts according to the kinematics of the process is similar to grinding. The strengthening process was carried out on an upgraded surface grinder. The tool is a metal disk made of stainless-steel. Transverse grooves are formed on the working surface of the tool to intensify the process of forming a strengthened (reinforced) layer with a nanocrystalline structure. The grooves form additional shock loads in the contact area of the tool-treatment surface of the part. These shock loads increase the shear deformation of the metal of the parts’ surface during treatment, which affects into formation the quality parameters of the parts’ surface and surface layer. To study the friction treatment process, the calculation scheme of the elastic system of the machine was developed. A simulation model for the study of dynamic processes that take place during the friction treatment of flat surfaces was built. This model gives possibility to determine the displacements and velocities of the machine table on which the part is fixed and the tool, and to determine their mutual displacement and also calculate the reaction of the machine table.
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    Analysis of modern investigations of vibratory processes of wheeled vehicles
    (Publishing House of Lviv Polytechnic National University, 2016) Zalutskyi, Yurii; Zhytenko, Oleksandr; Kuzio, Ihor
    The history and modern tendencies of development of cushioning systems are analyzed in this paper. The development of mathematical modelling as a process is denoted, the methods and means are described and the necessary information of model choosing is presented. It is focused on the development of simulation modelling. The approaches of researchers, recommendations, indexes and specific features of evaluation of motion evenness are described. The works of many scientists are dedicated to analysis of car vibrations, evaluation of motion evenness and vibration-proof features. Many of them are devoted to investigation of vibrations, to optimization of basic design parameters of the cushioning system of cars and to development of new cushioning systems which allow reducing of vibratory overloading of trucks of general purpose. Taking into account the problems of motion evenness from the point of view of vibration of cushioning parts, the works of scientists are based on the linear theory of cushioning and the simplest one-mass car models are considered. It is also established that the drawback of usage of such theory consists in the fact that it is impossible to overview separately the vibrations of cushioning parts, which weight transfers to elastic elements of the suspension, and non-cushioning parts. The overview of scientific works dedicated to investigation of dynamics of wheeled vehicles allows to show the limited possibilities of traditional passive suspension system according to continuously increasing requirements to modern structures and to substantiate the necessity of usage of controlled cushioning systems. Among the existing variants of controlled cushioning systems, the half-controlled systems, which are the most optimal from the point of view of motion evenness increasing, energy consumption, complexity of structural implementation and usage safety, are of the greatest interest nowadays. On the basis of analyzed materials, it may be concluded that there exists a great amount of scientific investigations in the field of motor vehicles vibrations many of which are devoted to improvement of vibration-proof features of cars. Also a number of works are dedicated to investigation of vibratory overloading of industrial, construction and agricultural motor vehicles which are engaged in transportation of cargo of general purpose. However, too small attention is payed to development of techniques of determination of design parameters of cushioning systems of trucks which are engaged in transportation of cargo of special purpose, for example, cars transportation, where essentially greater attention should be payed to vibratory loadings which act upon such cargo during uneven motion.
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    Nonlinear analysis in synthesis of the resonant vibro-impact systems
    (Publishing House of Lviv Polytechnic National University, 2015) Gursky, Volodymyr; Kuzio, Ihor
    The paper considers differential equation of the vibro-impact resonance system with an asymmetric piecewise linear elastic characteristic. The time-instant of switching of elastic characteristic is determined on the basis of equality of oscillation period to average value of the corresponding eigenfrequencies. Then, expansion of the asymmetric piecewise linear elastic characteristic into Fourier series was made. The initial differential equation was reduced to a kind of parametric equations of Hill’s andMathieu’s type with taking into account the time of elastic characteristic change. Stability analysis of parametric Mathieu equation is shown for the analysis of natural oscillations. For stability analysis of the synthesized by various stiffness coefficients of vibro-impact system, dependencies of Mathieu equations coefficients on the parameter of synthesis are used. The solution of the initial equation with forced oscillations in the form of asymmetric two-frequency vibrations has been obtained by means of Bubnov-Galerkin and Levenberg-Marquardt methods for nonlinear algebraic systems of equations, also amplitude and phase frequency dependence was graphically drawn. The basic equation with an asymmetric elastic response characteristic feature is determined by the fixed natural frequency of oscillations independently of amplitude. Numerical solution of differential equations by means of Runge–Kutta method are presented for comparison. Comparison of the vibro-impact resonance system kinematics characteristics, synthesized by the elastic parameters and solved by the listed methods, is conducted. The feasibility of using nonlinear analysis presented in two harmonics in Fourier series asymmetric elastic characteristic is justified in the article. The suggested approach with Bubnov-Galerkin method for general Hill’s equation and correlation analysis of time kinematic characteristics was used. Acceleration frequency spectrum and harmonics are obtained on the basis of Runge–Kutta numerical method simulation of the initial nonlinear differential equation.