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Multitilting-pad journal bearings (MTPJBs) used in large-scale hydraulic turbines often suffer from complex operating conditions, which greatly influence the overall performance of the rotating machine. The purpose of this study is to establish a thermal-elastic-hydrodynamic lubrication model for MTPJBs that can predict the static and dynamic characteristics of high-speed and heavy-load MTPJBs under different operating conditions.

A thermo-elasto-hydrodynamic lubrication model considering the turbulence effect is proposed for high-speed and heavy-load TPJBs, which is solved using the coupled finite difference method and finite element method. The model considered the turbulence effect, thermal energy diffusion, viscosity–temperature–pressure relationship and elastic deformation of the pads. The influences of the operating conditions on static and dynamic characteristics of tilting pad journal bearings were analyzed in depth.

The operating conditions have a strong effect on the static properties of the bearings. The dynamic characteristics of the TPJB were the most influenced by the shaft speed. The effects of the load direction on the dynamic properties of the TPJB were much stronger than those of the static characteristics.

This study used analytical methods and models to provide theoretical guidance for evaluating lubricating characteristics, assembling conditions and overall health.

The purpose of this study is to investigate the hydrodynamic characteristics of journal bearings in a high-speed and heavy-load press system by considering thermal influence and cavitation.

A proper and effectual computational method is presented for steady-state analysis of fluid interaction in a rotor-bearing press system by combining computational fluid dynamics techniques.

The influences of eccentricity ratio, rotational speed and oil-film thickness on the hydrodynamic behavior of the journal bearing are studied.

The computational method can be used for creating a precise lubrication design for a journal bearing of a lubrication system.

Hydrostatic thrust bearing is a key component of the vertical CNC machining equipment, and often results in friction failure under the working condition of high speed and heavy load. The lubricating oil film becomes thin or breaks because of high speed and heavy load and it affects the high precision and stable operation of the vertical CNC machining equipment; hence, it is an effective way of avoiding friction failure for achieving the oil film shape prediction

For the hydrostatic thrust bearing with double rectangular cavities, researchers solve the deformation of the friction pairs in hydrostatic bearing by using the computation of hydrodynamics, elasticity theory, finite element method and fluid-thermal-mechanical coupled method. The deformation includes heat deformation and elasticity deformation, the shape of gap oil film is got according to the deformation of the friction pairs in hydrostatic bearing, and gets the shape of gap oil film, and determines the influencing factors and laws of the oil film shape, and achieves the prediction of oil film shape, and ascertains the mechanism of friction failure. An experimental verification is carried out.

Results show that the deformation of the rotational workbench is upturned along its radial direction under the working condition of high speed and heavy load. However, the deformation of the base is downturned along its radial direction and the deformation law of the gap oil film along the radius direction is estimated; the outer diameter is close but the inner diameter is divergent wedge.

The conclusion can provide a theoretical basis for the oil film control of hydrostatic thrust bearing and improve the stability of vertical CNC machining equipment.

Previous studies were mainly focused on profile designation of bearing rollers and lubrication performance without considering roller-races skidding. However, the width of round corner, load, rotational speed and some other parameters have significant effects on the roller-races sliding speed. This paper aims to investigate the effect of round corner on lubricating characteristics between the heavily loaded roller and inner race considering skidding and roughness.

A mixed elastohydrodynamic lubrication (EHL) model which is capable of handling practical cases with 3D machined roughness is combined with the skidding model to investigate the effect of round corner on lubricating characteristics between the heavily loaded roller and inner race.

The width of round corner and round corner radius have a desirable range under certain operating condition, within which the maximum pressure, stress and maximum flash temperature remain low. The optimized range is sensitive to the operating condition. Roughness and skidding narrow the optimized range of round corner radius. Roughness increases the pressure peak, Mises stress and friction coefficient. At the same time, skidding and roughness have obvious effects on film thickness at the contact center area if the round radius is small.

This paper uses the Harris skidding model that has a relatively bigger error, which is not accurate if the bearing load is less.

This paper unifies the skidding model and mixed EHL model which can be used as a tool for optimization design and lubricating performance analysis of cylindrical roller bearing.

Lubrication analyses for roller bearing are assumed to be pure rolling contact between roller and races in a previous study, which could not reflect the real contact characteristics. The skidding model is merged into a mixed EHL model which can be used as a dynamic tool to analyze the lubricating performance considering the round corner, skidding and roughness.

The purpose of this paper is to prepare a novel nano magnetic grease with favorable lubricating performance; to contrast the tribology performance of the magnetic grease with the original grease, and to find the lubricating mechanism of the magnetic grease.

The nano Fe₃O₄ magnetic fluids are added into the general urea grease to synthesize the nano magnetic grease. Tribology performance tests of the magnetic grease and the original grease are contrasted on a MMW‐1 four‐ball tester. Based on three kinds of effects caused by the nano magnetic fluids, the lubricating mechanism of the magnetic grease is discussed.

Nano magnetic grease with favorable lubricating performance can be synthesized by adding the nano Fe₃O₄ magnetic fluids into the general urea grease. The nano magnetic grease has better lubricating performance and more steady bearing capability than the original grease, and is especially available for the lubricating of equipment with high speed and heavy load. The performance improvement of the magnetic grease is owing to the interactions of three kinds of effects as follows: the viscosity increasing effect, the micro‐rolling effect, and the friction weakening effect, which are all caused by the nano magnetic fluids added into the grease.

The paper documents that the nano Fe₃O₄ magnetic fluids added into the urea grease to synthesize a novel nano magnetic grease has been proved to have quite favorable lubricating performance by the tribology experiments, and the lubricating mechanism of the magnetic grease is also discussed.

This paper aims to describe a theoretical and experimental research concerning influence of recess shape on comprehensive lubrication performance of high speed and heavy load hydrostatic thrust bearing with a constant flow.

The lubrication performance of a hydrostatic thrust bearing with different recess shape under the working conditions of high speed and heavy load has been simulated by using computational fluid dynamics and finite volume method.

It is found that the comprehensive lubrication performance of a hydrostatic thrust bearing with circular recess is optimal. The results demonstrate that recess shape has a great influence on the lubrication performance of the hydrostatic thrust bearing.

The simulation results indicate that to get an improved performance from a hydrostatic thrust bearing with constant flow, a proper selection of the recess shape is essential.

This study aims to evaluate the rheological properties of aviation lubricating oil under conditions of heavy load, high speed and high temperature and the applicability of the classical rheological model under severe conditions.

A Chinese aviation lubricating oil was used and its traction curves were obtained using a new two-disk tribotester. Its rheological parameters were calculated based on empirical formulae. Moreover, the traction force was calculated based on the classical Eyring rheological model.

The traction curves are obtained with respect to contact pressure, temperature and rolling speed. The rheological parameters are significantly influenced by environmental factors, especially viscosity. The traction force calculated using the Eyring model is consistent with the experimental results.

A novel two-disk tribotester was designed using a gas bearing and speed–force closed-loop control to ensure measurement accuracy. The mechanism of rheological properties was analyzed and the applicability of the classical rheological model under severe conditions was verified. It provided an experimental and theoretical basis for expanding the application of classical rheological models under extreme conditions.

The traction behaviours of lubricating oil significantly affect the stability and lubrication regime of aviation high-speed ball bearings. Rolling elements will slide at a low traction force (TF). Therefore, traction behaviours need to be studied, and a fitting expression for traction curves to rapidly calculate the traction coefficient (TC) should be developed.

The traction behaviours of an aviation lubricating oil were studied in severe operating conditions with a self-designed two-disc testing rig. Based on the least squares method and the Levenberg–Marquardt theory, a rapid calculation expression was developed by fitting the obtained traction curves. The correction of this expression was experimentally verified by comparing the TCs under different operating conditions. This expression was also used to modify the commonly accepted quasi-dynamic model of rolling bearings.

An increase of the load led to an increase in the TC. In comparison, the temperature and entrainment speed showed inverse effects. The proposed expression exactly predicted the trend of the experimentally acquired traction curve. The calculation with the modified dynamic model showed that the action of the TF on a single rolling element varied and that the temperature increase of the outer raceway is higher than the inner raceway, which is caused by the TF and relative sliding speed between the elements and raceways.

The proposed fitting expression is able to simplify the TC calculation of synthetic aviation lubricating oil in practical engineering applications. This paper can provide an important reference for the traction behaviour of synthetic aviation lubricating oil under severe conditions and assist with its rapid calculation and practical application in engineering.

The breakdown of laminar flow in the clearance space of a journal is considered, and the point of transition is considered in relation to experiments carried out with ‘bearings’ of large clearance. Experiments involving flow visualization with very large clearance ratios of 0.05 to 0.3 show that the laminar regime gives way to cellular or ring vertices at the critical Reynolds number predicted by G. I. Taylor for concentric cylinders even in the presence of an axial flow and at a rather higher Reynolds number in the case of eccentric cylinders. The effect of the transition on the axial flow between the cylinders is small. The critical speed for transition as deduced by Taylor, is little affected by moderate axial flows and is increased by eccentricity. The effect of critical condition on the axial‐flow characteristics of the bearing system appears to be negligible, again for moderate axial flows. Assuming that the results can be extrapolated to clearances applicable to bearing operation, the main conclusion of this paper is that the breakdown of laminar flow, which is a practical possibility in very high‐speed bearings, is delayed by eccentric operation.

AT THE INTERNATIONAL CONFERENCE ON GEARING arranged by the Institution of Mechanical Engineers in London from the 23rd to 25th September, a special session was set aside for the Discussion of Lubrication and the following papers were presented :—