Browsing by Author "Javorova J."

Now showing 1 - 7 of 7
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    A comparative study on tribological behavior between metal and polymeric composites used to repair bronze made parts in dry reciprocating sliding tests
    (2017-03-01) Iliuţǎ V.; Ripǎ M.; Javorova J.; Andrei G.
    The paper presents the researches on tribological behaviour of two materials used for parts subjected to friction, under dry sliding conditions. The composite material is a product of the company Diamant Metallplastic GmbH, Germany and the manufacturer recommend it for repairing or reconditioning worn or damaged bronze made parts. The material belongs to Multimetall category, which is a highly resistant 2-component repair system. This polymer composite material was tribologically tested in dry friction reciprocating conditions, in ball-on-flat configuration, using the tribometer UMT-2 (Bruker, former CETR). The counterpiece was a steel ball. Typical test conditions were as follows: normal loads of 20, 30, 40 and 50 N, sliding distance of 100 m, stroke length of 5mm, average sliding speed of 3,5 mm/s, room temperature and relative humidity of 50-60%. After testing, wear tracks were examined by electronic microscopy (SEM), laser profilometry and the profilometric module of the tribometer CETR-UMT-2. The results of the composite material analysis were compared with the similar ones obtained under similar test conditions for the bronze (metal material).
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    Ball-on-flat reciprocating test to evaluate dry sliding wear behaviour of reinforced polymer composites
    (2020-01-11) Iliuta V.; Ripa M.; Javorova J.; Andrei G.
    This paper presents the results of the tribological investigations on polymeric composite materials reinforced with Cu, Zn, Sn, SiO2 and MoS2 microparticles, used for repairing metal parts made of brass and bronze. The tested material were: Three composite materials (products of the company Diamant Metallplastic GmbH, Germany): Multimetall Messing (used for repair of brass parts), Multimetall Bronze (used for repair of bronze parts) and Moglice (for brass and bronze parts). The testing was conducted in dry conditions, in ball on flat configuration, by reciprocating method, on the CETR UMT-2 tribometer (Bruker Corporation) at normal loads 20, 30, 40 and 50N, over a sliding distance of 100m. The paper presents studies of the variations of the friction coefficient, linear wear, volumetric wear parameters, profilometric studies with SEM surface morphologies of the wear tracks. The researches allowed the classification of materials according to their tribological behaviour and the results recommend the tested reinforced composite materials as good candidates for repairing metal parts made of brass or bronzes.
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    Effects of fluid inertia and bearing flexibility on the performance of finite length journal bearing
    (2017-03-01) Javorova J.; Alexandrov V.
    The paper describes the theoretical study concerning the effect of lubricant inertia forces and deformability of the bearing elastic layer on the performance of a plane journal bearing. The problem is investigated for a Newtonian lubricant under isothermal and isoviscous conditions. The analysis considers the generalized Reynolds equation governing the flow of lubricant in the clearance space and the linear elasticity equation governing the displacement field in the bearing shell. An iterative numerical procedure with successive over relaxation is used to pressure distribution within the lubricated conjunction. Bearing performance characteristics have been presented for typically selected values of generalized Reynolds number Re∗ and elasticity parameters of the elastic liner. It has been observed that the combined effect of fluid inertia forces and bearing flexibility affects the performance characteristics of dynamically loaded journal bearing.
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    ELASTOHYDRODYNAMIC EFFECTS IN LUBRICATION OF JOURNAL BEARINGS UNDER TURBULENT CONDITIONS
    (2024-01-01) Javorova J.; Andonov I.; Severin T.; Irimescu L.; Rakanov Y.
    The current paper is aimed to investigate the deformability effects of the bearing surface on the lubrication performance of cylindrical journal bearing with finite length under turbulent conditions. The bush is coated with a thin resilient layer with a smooth surface, the radial distortions of which are of the same order of magnitude as the film thickness. The elastohydrodynamic problem is studied under elasticity conditions in accordance with the plain strain hypothesis (Winkler model). The modified Reynolds equation is carried out on the base of the turbulent lubrication model of Hirs (bulk flow model). The partial differential equation is solved numerically by successive over-relaxation technique on a finite difference grid, considering different values of coating materials, lubricant viscosity, and journal speed. Results for the performance characteristics of the bearing are given for several selected values of Reynolds number and elasticity parameters of the soft liner on the bush.
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    On the modified Reynolds equation for journal bearings in a case of non-Newtonian Rabinowitsch fluid model
    (2018-01-09) Javorova J.; Angelova J.
    In this paper, a theoretical analysis of hydrodynamic plain journal bearings with finite length at taking into account the effect of non-Newtonian lubricants is presented. Based upon the Rabinowitsch fluid model (cubic stress constitutive equation) and by integrating the continuity equation across the film, the nonlinear modified 2D Reynolds type equation is derived in details so that to study the dilatant and pseudoplastic nature of the lubricant in comparison with Newtonian fluid. A dimensionless equation of hydrodynamic pressure distribution in a form appropriate for numerical modeling is also presented. Some particular cases of 1D applications can be recovered from the present derivation.
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    Particularities of the pseudo-plastic lubrication, with application to the sinovial liquid
    (2016-02-25) Radulescu I.; Radulescu A.V.; Javorova J.
    The present paper proposes a new model for lubrication of the hip joint with hyaluronan solutions, considering the squeeze film process of non-Newtonian fluid between rigid spherical surfaces. The rheological model that approximately describes the behaviour of the synovial fluid is the power law model. For the considered case, the pressure distribution, the load capacity, the film thickness and the friction coefficient have been determinated. The conclusions of the paper offer an explication to the development of the osteoarthritis and to the problems of the arthritic patients.
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    Study of soccer ball flight trajectory
    (2018-01-09) Javorova J.; Ivanov A.
    In this paper the trajectories of a soccer ball for the most important kicks in the football game - a corner kick and a direct free kick are studied. The soccer ball is modelled as an ideal rigid hollow spherical body with six degrees of freedom, which performs a general motion in an immovable air environment with constant parameters. The ball 3D orientation is determined by the three Cardan angles. The aerodynamic forces and moments with which the air environment acts to the ball are taken into account. Two of the most dangerous areas of the football goal are defined. Differential equations which describe the motion of the soccer ball are solved numerically by MatLab-Simulink.