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To date few experimental studies of EHL film are at speed above 5 m/s, and most optical EHL experiment is based on classical ball-on-disc contact. This paper presents a newly developed optical EHL test rig in ball-on-ring contact for the investigation of film thickness at high speed. Tests are conducted under tractive rolling condition up to 52 m/s. Results show that, film thickness follows classical prediction at low speed, deviates but still increases at medium speed and finally decreases at very high speed; severe sliding occurs at high speed; the film thickness profile along motion direction changes from flat to wedge.

This paper presents a semi-analytical method (SAM) to solve sliding finite-length space contact problem with consideration of the effect of free end surface. The equation set based on the overlapping concept is analytically solved with tangential load considered and the explicit expressions for equivalent mirrored loads are obtained. Conjugate gradient method (CGM) is adopted to solve the pressure distribution and Fast Fourier transform (FFT) is used to speed up stress related calculation. The model is verified by FEM and shows a high conformity. Different line contact situations are discussed to explore the effect of free end surfaces.

This paper aims to investigate the effect of the hardness distribution by carburizing on the contact behaviors. A developed elastic–plastic contact model based on a semi-analytical method is used. The effect of hardness on elastic–plastic contact behaviors is considered by means of the linear hardness-yielding strength relationship. Different hardness distributions are considered to simulate the possible results obtained in heat treatment. The results show that the hardness distribution and carburizing time/case depth have different influence on the plastic strain under different loads and roughness, while its influence on the maximum contact pressure and contact area ratio is very limited.

This paper proposes a dynamic model to investigate skidding in angular contact ball-bearings with considering the interaction between balls and raceways, cage and lubricant. The differential equations governing the motions of bearing elements are established and solved using a fourth-order Runge–Kutta algorithm; traction forces between balls and raceways are evaluated based on elastohydrodynamic lubrication theory. The results show that the applied axial load significantly influences the behavior of skidding due to the changes of internal load, orbital and rotation speeds of ball under different operating conditions; appropriate axial load can be determined to avoid severe skidding.

Modeling study of angular contact ball bearing, which is subjected to a combined action of radial, axial and moment loads, is performed in this paper. The centrifugal force and the gyroscopic moment are especially considered. To analyze the spin-to-roll ratios at both ball-outer and ball-inner raceway contacts simultaneously, the model discards the hypothesis of “raceway control” by introducing a controlling equation of ball pitch angle. The method simplifies the solution procedure involved in determining ball equilibrium equations. Numerical examples verify the model and show its capabilities in predicting the bearing characteristic parameters such as contact angle, contact force and spin-to-roll ratio under various operating conditions. It is also shown that the effect of the centrifugal force is of significant importance that should not be neglected in the design and analysis of rolling bearings, especially at high-speed conditions.

Rough surface elastic–plastic contact performance is investigated in this paper. First, a computer program is developed to generate rough surfaces with given parameters; Then, the elastic–plastic contact model is developed based on minimization of complementary energy and semi-analytical method; finally, contact analysis for rough surfaces are conducted. The results show that kurtosis and skewness have significant effects on the contact performance under light-medium load; for heavy load condition and small skewness, the contact characteristic parameters change slightly along with kurtosis. Comparing with elastic contact, the low contact pressure and large contact area are predicted in elastic–plastic contacts.

Elastohydrodynamic lubrication (EHL) analysis in finite line contacts is usually modeled by a finite-length roller contacting with a half-space, which ignores effect of the two free boundaries existing in many applications such as gears or roller bearings. This paper presents a semi-analytical method, involving the overlapping method and matrix formation, for EHL analysis in the finite line contact problem to consider the effect of two free end surfaces. Three half-spaces with mirrored loads to be solved are overlapped to cancel out the stresses at expected surfaces, and three matrices can be obtained and reused for the same finite-length space. The isothermal Reynolds equation is solved to obtain the pressure distribution and the fast Fourier transform (FFT) is used to speed up the elastic deformation and stress related calculation. Different line contact situations, including straight rollers, tapered rollers, and Lundberg profile rollers, are discussed to explore the effect of free end surfaces.

Oil–air lubrication is widely used in the high-speed rotary machines; the oil is usually in the form of discrete droplets. The lubrication behavior of the oil droplet is rarely investigated. This paper investigates the effect of the oil droplet on lubrication performance based on the developed transient lubrication model with consideration of starvation conditions. The oil droplet is modeled as spherical segment with different heights, base radius, and positions, which will change the inlet oil supply conditions. The results show that the oil droplet with large size can generate thick oil film which is close to the one in fully flooded condition and can remain long time; the position of the oil droplet entering the contact region also has significant effect on the lubrication performance.

Finite-length line contact conditions, existing in applications such as gears or roller bearings, lead to subsurface stress distribution influenced by the free boundaries. This paper presents a semi-analytical method (SAM) for the finite-length line contact problem, based on the overlapping concept and matrix formation, to consider the effect of two free-end surfaces. In order to obtain two free surfaces, three half-spaces with mirrored loads to be solved are overlapped to cancel out the stresses at expected surfaces. The error introduced by this method is analyzed and proven to be negligible. The conjugate gradient method (CGM) is used to solve the pressure distribution, and the fast Fourier transform (FFT) is used to speed up the elastic deformation and stress-related calculation. The model is verified by finite element method (FEM) and shows a high conformity and efficiency. Besides, the line contact situations are discussed to explore the effect of free surfaces.