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Surface plastic deformation due to contact (lubricated or dry) widely exists in many mechanical components, as subsuiface stress caused by high-pressure concentrated in the contact zone often exceeds the material yielding limit, and the plastic strain accumulates when the load is increased and/or repeatedly applied to the swface in a rolling contact. However, previous plasto-elastohydrodynamic lubrication (PEHL) studies were mainly for the preliminary case of having a rigid ball (or roller) rotating on a stationary elastic-plastic flat with a fixed contact center, for which the numerical simulation is relatively simple. This paper presents an efficient method for simulating PEHL in a rolling contact. The von Mises yield criteria are used for determining the plastic zone, and the total computation domain is discretized into a number of cuboidal elements underneath the contacting swface, each one is considered as a cuboid with uniform plastic strain inside. The residual stress and sutface plastic deformation resulted from the plastic strain can be solved as a half-space eigenstrain-eigenstress problem. A combination of threedimensional (3D) and two-dimensional (2D) discrete convolution and fast Fourier transform (DC-FFT) techniques is used for accelerating the computation. It is observed that if a rigid ball rolls on an elastic-plastic swface. the characteristics of PEHL lubricant film thickness and pressure distribution are different from those of PEHL in the preliminary cases previously investigated. It is also found that with the increase of rolling cycles, the increment of plastic strain accumulation gradually approaches a stable value or drops down to zero, determined by the applied load and the material hardening properties, eventually causing a groove along the rolling direction. Simulation results for different material hardening properties are also compared to reveal the effect of body materials on the PEHL behaviors. [ABSTRACT FROM AUTHOR]

Benefits of suiface textures for improving the peifornutnce behaviors of tribo-contacts are being explored and established by the investigators across the globe. But the consolidated information of findings of such explorations are spread. Therefore, the objective of this paper is to summarize the information available related to the preparation of surface textures and performance outcomes in the presence of suiface textures at the concentrated contacts. Mainly, recent research findings and practices followed for the study oj friction, wear, lubrication, contact fatigue, vibration, and noise at the generic concentrated contacts in presence of suiface textures are reviewed for current status of research in the area and outlining the future prospects. [ABSTRACT FROM AUTHOR]

This paper concludes a series of papers outlining a new rolling-element bearing heat transfer model. Part I provided the mode! framework. Part II presented the partial differential equation (PDE) solutions, and Part III. this paper, presents full-scale test results for ball, cylindrical, spherical, and tapered rolling-element bearings. The results validate the heat partitioning equation and the predicted solid temperatures for circulating oil lubrication. In addition, sump lubrication was studied using an acrylic assembly. The results quantify what fraction of the bearing periphery is cooled by oil, as well as the flow of oil through a bearing. Finally, substantiation of the modeling assumptions is discussed. [ABSTRACT FROM AUTHOR]

Part I of this three-part series presented a heat transfer rolling-element bearing model. The model is composed of solid conduction partial differential equations (PDEs), control volume formulation for lubricant temperatures, and heat partitioning. The model applies to systems with a shaft, housing, numerous bearings, gears, and various methods of lubrication. Part II, this work, presents a solution to the thermal conduction equations. The raceways are three-dimensional (3D), the shaft and housing models are two-dimensional (2D) and lumped in the third direction. This generalized method applies to ball, cylindrical. spherical, and tapered rolling-element bearings. Semi-analytic solutions are obtained by imposing integral transforms. This approach accounts for the axial and circumferential variations in the bearing load zone and rib heating, as well as the ability to link many bearings and gears within an assembly. The housing and shaft equations are radially lumped. The lumped fluxes account for internal and external convection and radiation, as well as conduction fluxes from contiguous bearings and gears. These equations are solved using a Fourier transform. The 3D bearing raceway solution uses a Fourier transform and a modified Hankel transform. Part 111 of this series presents additional results and experimental validation. [ABSTRACT FROM AUTHOR]

Lubricating grease is commonly used for lubricating "sealed and greased for life" rolling element bearings. This grease also provides an additional sealing function to protect the bearing against ingress of contaminants. In this work the sealing function of lubricating grease in the vicinity of the seal lip contact has been studied experimentally by measuring the migration of spherical fluorescent contaminant particles in the vicinity of the contact, as a function of shaft speed and lubricant type. The experimental results reveal that in some greases contaminant particles migrate towards the sealing contact where the shear rate reaches its highest value. However, for other greases, Newtonian base oils, and elastic fluids, this is not necessarily the case and contaminant particles consistently migrate away from the sealing contact. Various physical phenomena have been investigated to explain the difference in migration behavior. It is concluded that migration towards the sealing contact is driven by the viscosity gradient and migration away from the sealing contact is related to the Weissenherg number. The sealing function of grease in the vicinity of the sealing contact is due to the migration of contaminant particles. The migration reduces the probability of particles to reach the sealing and hearing contacts. [ABSTRACT FROM AUTHOR]

A baseline theory is developed in this paper for the design of oil-lubricated centrally pivoted plane-pad thrust bearings. By focusing on the hydrodynamics generated by the viscosity-temperature effects of the lubricating oil, a mathematical model is derived with a single dimensionless parameter Wth. The nominal value of Wth is 0.1 for typical pad bearings in current industrial practice. The theory suggests two important design calculations for centrally pivoted plane-pad bearings: (1) The minimum oil film thickness in the bearing is about 0.65 of the film thickness determined using the classical isothermal lubrication theory with the pad pivoted at the maximum-load optimum location. Thus, by setting the film thickness to 1.54 times the design requirement, one may carry out design selections and calculations using the classical theory (2) The friction in the bearing is about 1.7 times the value determined using the classical theory at the maximum-load optimum condition and with the film thickness equal to the design requirement. Thus, one may also use the classical theory to meaningfully calculate the friction and power loss in the centrally pivoted plane-pad bearing systems. The theory is developed based on fundamental lubrication science, order of magnitude analyses of the assumptions, and supporting evidence from numerical literature case studies. It would be a conservative baseline theory for the bearing design as other complicated and/or incidental mechanisms would help provide a design factor of safety. [ABSTRACT FROM AUTHOR]

A running torque analysis was performed on axially loaded deep groove ball bearings lubricated with a polymer lubricant. The analysis included a Type I and a Type II bearing. The Type I bearing has a stamped steel riveted cage with its cavity packed with the polymer lubricant. The ball surface, except for the contact points of the ball and the raceways, was covered with the polymer lubricant. The Type II bearing had the polymer lubricant packed only on the riveted parts of the cage; the balls were not covered with the polymer lubricant. The analysis was applied to a 6206 deep groove ball bearing axially loaded in a range typical of preloads applied in actual application to this size bearing to establish bearing tare torque. The results were compared to an available database. The running torque formulas for deep groove ball bearings with polymer lubricant under axial load were proposed as the sums of the running torque caused by the shearing resistance of the mineral oil between the bearing rings and the polymer lubricant, the elastic hysteresis, the differential slip, the spinning friction of the balls, the elastohydrodynamic lubrication (EHL) viscous rolling resistance, and the friction between the balls and the polymer lubricant (or the cage). The effects of the sources of the running torque were investigated. In the case of the Type I bearing, the running, torque caused by the friction between the balls and the polymer lubricant, the EHL viscous rolling resistance, and the shearing resistance of the mineral oil between the bearing rings and the polymer lubricant significantly affect the running torque. In the case of the Type II Bearing, the running torque caused by the EHL viscous rolling resistance and the shearing resistance of the mineral oil between the bearing rings and the polymer lubricant significantly affect the running torque. A reasonable correlation exists between the analysis and the database. However, the analysis needs to be further validated with bearing data from different size deep groove ball bearings run under varying loads and speeds. [ABSTRACT FROM AUTHOR]

The influence of the transversely and/or longitudinally oriented surface waviness on the lubricating behavior in the rolling/sliding elliptic contact composed of two steel bodies and lubricated with a non-Newtonian lubricant was investigated theoretically with full numerical solution of the thermal elastohydrodynamic lubrication. The entrainment velocity was assumed to be along the minor axis of the Hertzian contact ellipse. The waviness of each surface was given by a sinusoidal function. The non-Newtonian flow of the lubricant was described by the Eyring model with a constant Eyring shear stress at the ambient pressure and temperature. The velocity of the faster surface was assumed to be four times as that of the slower surface in order not only to highlight the thermal and non-Newtonian effects, but also to ensure a cyclic solution when both surfaces were with transversely oriented waviness. Starting from a quasisteady solution, the cyclic time-dependent solution was achieved numerically time step by time step. The results show that the thermal and non-Newtonian effects can be enlarged significantly by the surface waviness, and the worst configuration of the surface topography is that both surfaces are with longitudinal waviness. [ABSTRACT FROM AUTHOR]

Many elastohydrodynamically lubricated contacts in practical applications, e.g., in bearings, operate in the starved lubrication regime. As a result their performance is sensitive to variations of the lubricant layers present on the surfaces, which form the supply to the contact. Their shape is often determined by previous overrollings of the track and also by replenishment mechanisms and various migration effects. Variations of the layers induced in the direction Of rolling lead to a time-varying lubricant supply to the contact. In this paper, by means of numerical simulations using a starved lubrication model, the film thickness modulations in the center of the contact induced by a harmonically varying inlet supply have been investigated. First, for a given load condition and layer wavelength, the effect of the nominal layer thickness (degree of starvation) and the layer variation amplitude is illustrated. Subsequently, using results for different load conditions, wavelengths, and degrees of starvation, it is shown that the response of the contact to such variations is determined by a nondimensional parameter, which represents the ratio of the entrainment length of the contact to the wavelength of the induced variation, and by the degree of starvation. A simple formula is presented for use in engineering predicting the ratio of the amplitude of the film modulations in the center of the contact to the amplitude of the layer variations in the inlet. [ABSTRACT FROM AUTHOR]

Indents perturb the pressure and stress distribution and increase the failure risk of rolling element bearings. A numerical study of the pressure perturbation is proposed. An existing dry contact model is extended to account for the indent shoulder influence and the pressure collapse in deeper indents. Moreover, results for pure rolling lubricated contacts are presented. Finally, the ellipticity influence is studied for both dry and lubricated contacts. [ABSTRACT FROM AUTHOR]

Rolling element bearings find widespread domestic and industrial application. Defects in bearing unless detected in time may lead to malfunctioning of the machinery. Different methods are used for detection and diagnosis of the bearing defects. This paper is intended as a tutorial overview of bearing vibration signature analysis as a medium for fault detection. An explanation for the causes for the defects is discussed. Vibration measurement in both time domain and frequency domain is presented. Recent trends in research on the detection of the defects in bearings have been included. [ABSTRACT FROM AUTHOR]