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An analysis of the dynamic behavior of hybrid journal bearings is presented. The analysis accounts for the compressibility of the lubricant in the bearing recesses and supply line. Results show that when the journal is subjected to high frequency excitation the bearing stiffness and damping can change drastically. The behavior is characterized by a “break frequency” beyond which the bearing stiffness increases sharply. This is accompanied by a rapid decrease in bearing damping. It is also shown that the cross-coupling stiffness coefficients are reduced at high excitation frequencies. The asymptotic behavior of the stiffness and damping coefficients is examined at both ends of the frequency spectrum.

The thermoelastohydrodynamic (TEHD) behavior of a finite inclined-plane slider bearing is studied. The fluid film momentum, continuity, and energy equations are coupled to the heat conduction equations and the elasticity equations of the solid, and solved numerically. The elastic and thermal distortions of the solid as well as the variation of fluid properties with temperature are considered in the analysis. Several models for the bearing solids are treated.

The thermohydrodynamic (THD) performance of finite slider bearings is studied under nonsteady-state conditions. The fluid film energy, momentum and continuity equations are coupled to the heat conduction equation for the bearing solids and the mathematical system is solved numerically to yield the fluid film temperature-time and load capacity-time histories. The effect of isothermal and adiabatic conditions at the fluid-solid interface is presented. The bearing transient response to constant and time-dependent runner speeds is also discussed.

A new rheological model for lubricants containing additives having long molecules is presented. The viscosity of the fluid is assumed to depend on the angle between the viscous forces and the velocity vector at each point in the lubricating film. The characteristics and consequences of this model are discussed qualitatively and quantitatively. Results far a finite slider bearing lubricated with such a lubricant are presented.

This paper presents an analysis of the thermohydrodynamic performance of squeeze films. The mathematical model consists of a 3-dimensional Reynolds equation, a 3-dimensional time dependent energy equation, and a 3-dimensional time dependent heat conduction equation. The system of equations is solved numerically. Fluid film pressure and temperature distributions and the temperature distribution in the solids are presented. Fluid film velocity profiles as a function of time are also shown. The load-time characteristics for different operative conditions are studied. It is shown that a thermohydrodynamic squeeze-film parameter can give rise to a phenomenon which radically changes the fluid film performance.

An analysis of the steady state and dynamic characteristics of floating ring journal bearings has been performed. The stability characteristics of the bearing, based on linear theory, are given. The transient problem, in which the equations of motion for the bearing system are integrated in real time was studied. The effect of using finite bearing theory rather than the short bearing assumption was examined. Among the significant findings of this study is the existence of limit cycles in the regions of instability predicted by linear theory. Such results explain the superior stability characteristics of the floating ring bearing in high speed applications. An understanding of this nonlinear behavior, serves as the basis for new and rational criteria for the design of floating ring bearings.

This paper discusses new approximate solutions to Reynolds equation. A generalized short bearing approximation is developed which is applicable to a large class of hydrodynamic bearings. Several examples are presented and comparisons between approximate results and the exact solutions for finite bearings are made.

The dynamic responses of squeeze films to fluctuating loads are compared for the cases of rigid, elastic, and viscoelastic bounding surfaces. Unexpected and interesting differences are observed. These include the oscillatory response of indenter position to a non-negative fluctuating load and the decaying load versus time response to a prescribed indenter trajectory which remains constant over a period of time. Practical implications of these responses are noted. The transient analysis procedure, while general, is applied to a simple geometrical and physical model: an isoviscous Newtonian fluid squeezed between circular, initially flat, three-element viscoelastic Winkler solids. Surface deformation rate and film rupture are incorporated. The fully implicit numerical method utilizes a generalized Newton scheme together with finite element spatial discretization.

The quest to improve the fuel economy of General Motors passenger cars has led to the investigation of an engine-flywheel hybrid powertrain at the GM Research Laboratories (GMR). An engine-flywheel system was designed for a compact car and its performance was predicted analytically. The sytem was estimated to achieve an improvement in EPA composite fuel economy of 13 per cent ooer a 1984 production compact car. This margin of improvement was judged insuficient to justify the complex drivetrain, and, therefore, a prototype system was not built. However, the current potential of engine-flywheel hybrids for GM passenger car applications has been defined, and the technology areas requiring additional research attention have been identified.

The finite-element method is used to solve the compressible Reynolds equation which governs the fluid flow between the journal surface and the leaves in a multileaf journal bearing. The solution obtained is then coupled with the load-deflection equations of the leaves to obtain such information as liftoff speed and minimum film thickness. In addition, the load-deflection equations yield the initial preload on the journal, the startup torque, the stiffness coefficients, and the equivalent damping coefficients. Such details as leaf curvature, friction between leaves, and between leaves and journal surface are considered in the load-deflection equations. Results are obtained for a wide range of operating parameters.

This paper contains an analysis of a class of elastohydrodynamic squeeze film problems. A true transient analysis is presented. Thick films bounded by a finite rigid plate and a compliant half-space are considered. The effect of different approach constraints is explored, among these being constant and time varying load and constant and time varying center point pressure. The effect of different material models is also considered.

The thermohydrodynamic (THD) performance of finite inclined-plane slider bearings is studied. The fluid film momentum, continuity, and energy equations are coupled to the heat-conduction equations for the bearing solids, and solved numerically. The effect of bearing geometry, oil type, and inlet temperature on bearing performance is shown. The manner in which environmental temperature and heat transfer considerations influence the fluid film behavior is studied.

By the use of a new variational technique, the bearing profile which maximizes the load carrying capacity of an infinite length journal bearing is obtained. The lubricant is assumed to be incompressible and of constant viscosity. The flow is assumed to be laminar and the optimization is based upon a minimum film thickness. The solution obtained is a concentric step bearing with a film thickness ratio of 1.812 and a ridge to pad ratio of 0.328. It is mathematically shown by the use of the “nonlocal” formulation that this step profile does yield a maximum among all profiles sufficiently “close.”

The film profile which minimizes the coefficient of friction and the film profile which minimizes the total friction force for a given load for a one-dimensional slider bearing are determined using a variational method. The lubricant is assumed to be incompressible and of constant viscosity. The flow is assumed to be laminar, and the optimization in the first case is based upon an assumed minimum film thickness. It is shown by the use of the nonlocal variational formulation that these profiles do yield a minimum among all admissible profiles.