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Author: search.filters.author.Hashimoto, HiromuSubject: search.filters.subject.Tribology

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    Theoretical Prediction of Journal Center Motion Trajectory in Two-Lobe Hydrodynamic Journal Bearings23
    (1995-01-01)
    Mongkolwongrojn, Mongkol
    ;
    Prabkaew, Chamlong
    ;
    Hashimoto, Hiromu
    In this study, the theoretical prediction of a journal center motion trajectory for high-speed rotors supported by two-lobe hydrodynamic oil film journal bearings is presented for three different values of the noncircular ratios, 7 = 0, 0.5 and 1.0. In order to obtain values for the oil film forces used in the equations of motion for rotor-bearing systems, the Reynolds equation governing the oil film pressure generated in the bearing gap was solved using the semianalytical finite-element method for each time step. Furthermore, for each time step, the nonlinear equations of motion for a rigid rotor supported by two identical aligned bearings were solved using the improved Euler integration method. From the numerical results, the relations between the journal center motion trajectory and the corresponding pressure distribution were examined theoretically, and the effect of the noncircular ratio on the stability of rotor bearing systems was clarified for the cases of both balanced and unbalanced rotors. © 1995, The Japan Society of Mechanical Engineers. All rights reserved.
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    Static Characteristics of High-Speed Slider Bearings Lubricated with Non-Newtonian Fluids (In the Case of Infinitely Long Bearings)
    (1995-01-01)
    Hashimoto, Hiromu
    ;
    Mongkolwongrojn, Mongkol
    In this paper, the static characteristics of infinitely long slider bearings lubricated with non-Newtonian fluids are examined theoretically by considering the fluid inertia effects. In the derivation of the modified Reynolds equation, the fluid inertia terms in the momentum equation for the lubricant film are averaged over the film thickness, and the Rabinowitsch empirical model is used as a constitutive equation of non-Newtonian fluids. Applying the modified Reynolds equation to the infinitely long slider bearings, the film pressure, load carrying capacity, friction force and inlet flow rate are obtained under various values of the dimensionless nonlinear factor and film thickness ratio, and the effects of fluid inertia on these static characteristics are discussed. © 1995, The Japan Society of Mechanical Engineers. All rights reserved.
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