Факультет електроніки та інформаційних технологій (ЕлІТ)
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Item Description of the Stationary Structural States of a Boundary Lubricant Making Use of the Relation between the Density-Modulation and Excess-Volume Order Parameters(Bogolyubov Institute for Theoretical Physics, 2021) Ляшенко, Яків Олександрович; Ляшенко, Яков Александрович; Liashenko, Yakiv OleksandrovychA second-order phase transition between the structural states of a boundary lubricant sandwiched between atomically smooth solid surfaces has been described in the framework of theLandau theory of phase transitions, by using the density modulation and the excess volumeas the order parameters. A relation between those order parameters is found. The stationarystates of a lubricant and their dependences on such control parameters as the lubricant tem-perature, the elastic strain in the lubricant layer, and the external load on the friction surfacesare studied. The melting kinetics was simulated in the framework of a mechanical analog ofthe tribological system with elasticity.Item Influence of Chemical Heterogeneity and Third Body on Adhesive Strength: Experiment and Simulation(Technical University of Berlin, 2021) Ляшенко, Яків Олександрович; Ляшенко, Яков Александрович; Liashenko, Yakiv Oleksandrovych; Li, Q.; Popov, V.L.We investigate experimentally and numerically the influence of chemical heterogeneity and of third-body particles on adhesive contact. Chemical heterogeneity is generated by chemical treatment of the contacting bodies changing locally the surface energy. For studying the influence of the third body, two types of particles are used: sand particles with various geometrical shapes and sizes, and steel spheres of equal radius. Dependencies of the normal force on the indentation depth at both indenting and pull-off as well as the evolution of the contact configuration are investigated. Corresponding numerical simulations are carried out using the boundary element method (BEM).Item Shape of a sliding capillary contact due to the hysteresis of contact angle: theory and experiment(University of Niš, Serbia, 2021) Popov, V.L.; Ляшенко, Яків Олександрович; Ляшенко, Яков Александрович; Liashenko, Yakiv Oleksandrovych; Starcevic, J.We consider a classical problem of a capillary neck between a parabolic body and a plane with a small amount of liquid in between. In the state of thermodynamic equilibrium, the contact area between the bodies and the liquid layer has a circular shape. However, if the bodies are forced to slowly move in the tangential direction, the shape will change due to the hysteresis of the contact angle. We discuss the form of the contact area under two limiting assumptions about the friction law in the boundary line. We also present a detailed experimental study of the shape of sliding capillary contact in dependence on the roughness of the contacting surfaces.Item Influence of spatial inhomogeneity on the formation of chaotic modes at the self-organization process(Bogolyubov Institute for Theoretical Physics, 2020) Ляшенко, Зінаїда Миколаївна; Ляшенко, Зинаида Николаевна; Liashenko, Zinaida Mykolaivna; Ляшенко, Яків Олександрович; Ляшенко, Яков Александрович; Liashenko, Yakiv OleksandrovychThe Lorentz system of equations, in which gradient terms are taken into account, has beensolved numerically. Three fundamentally different modes of evolution are considered. In thefirst mode, the spatial distribution of the order parameter permanently changes in time, anddomains of two types with positive and negative order parameter values are formed. In thesecond mode, the order parameter distribution is close to the stationary one. Finally, in thethird mode, the order parameter is identical over the whole space. The dependences of theaverage area of domains, their number, and their total area on the time are calculated in thefirst two cases. In the third case, the contribution of gradient terms completely vanishes, anda classical Lorenz attractor is realized.Item Influence of Tangential Displacement on the Adhesion Force Between Gradient Materials(Bogolyubov Institute for Theoretical Physics, 2020) Ляшенко, Яків Олександрович; Ляшенко, Яков Александрович; Liashenko, Yakiv Oleksandrovych; Ляшенко, Зінаїда Миколаївна; Ляшенко, Зинаида Николаевна; Liashenko, Zinaida MykolaivnaThe influence of a tangential displacement on the strength of the adhesive contacts betweengradient materials with different gradings of their properties has been studied. Variants witha controlled force (fixed load) and a controlled displacement (fixed grips) are considered. Arelationship between the normal and tangential critical force components at which the contact isdestroyed is obtained. It is valid within the whole interval of the gradient parameters, where thedetachment criterium is obeyed. The optimal parameters at which the adhesive contact strengthis maximum are determined. A case of detachment under the action of only the tangentialforce, i.e. when the normal force equals zero, is analyzed separately.Item Dynamical model of the asymmetric actuator of directional motion based on power-law graded materials(University of Niš (Republic of Serbia), 2020) Ляшенко, Яків Олександрович; Ляшенко, Яков Александрович; Liashenko, Yakiv Oleksandrovych; Борисюк, Вадим Миколайович; Борисюк, Вадим Николаевич; Borysiuk, Vadym Mykolaiovych; Popov, V.L.We consider an actuator whose driving bodies are made of Power-Law graded materials. The directional motion is generated by an asymmetric mechanism producing simultaneously vertical and horizontal oscillations of the indenter. The dynamic contact of gradient materials is described and the equation of motion for the drive is written down and analyzed. It is shown that the exponent of the elastic inhomogeneity significantly affects the average velocity of motion of the cargo, which can be dragged by the drive.Item Моделирование соударения упругой сферы с упругим полупространством с постоянным коэффициентом трения(Сумский государственный университет, 2017) Ляшенко, Яків Олександрович; Ляшенко, Яков Александрович; Liashenko, Yakiv Oleksandrovych; Литовка, С.С.В работе рассматривается столкновение упругой сферы с упругим полупространством с постоянным коэффициентом трения в зоне контакта. Также проанализирована упрощенная модель процесса столкновения, в которой контакт рассматривается как линейная пружина. В этом случае найдено аналитическое решение, которое дает представление об основных свойствах полной нелинейной модели.Item Экспериментальная проверка результатов модели соударения упругих тел(Сумский государственный университет, 2016) Ляшенко, Яків Олександрович; Ляшенко, Яков Александрович; Liashenko, Yakiv Oleksandrovych; Литовка, С.С.На основе анализа литературных источников выбран набор экспериментально измеренных зависимостей нормального и тангенциального коэффициентов восстановления от скорости падения сферического тела под разными углами к отражающей поверхности.Item Влияние упругих свойств контактирующих материалов на прерывистый режим граничного трения(Сумский государственный университет, 2016) Ляшенко, Яків Олександрович; Ляшенко, Яков Александрович; Liashenko, Yakiv Oleksandrovych; Манько, Наталія Миколаївна; Манько, Наталья Николаевна; Manko, Nataliia Mykolaivna; Карчов, В.В.В работе предложена теория граничного трения, основанная на теории фазовых переходов Ландау между структурными состояниями смазочного материала.Item Автоколивальний режим руху індентора в моделі наноструктуруючого вигладжування із урахуванням сухого тертя(Cумський державний університет, 2016) Ляшенко, Яків Олександрович; Ляшенко, Яков Александрович; Liashenko, Yakiv Oleksandrovych; Феденко, М.О.Наноструктуруюче вигладжування – один із перспективних сучас- них методів модифікації поверхонь деталей, що дозволяє покращити їх міцністіні характеристики [1, 2]. Причому ця методика дозволяє модифікувати поверхні готових деталей, що також обумовлює її під- вищену актуальність.