This paper presents a mathematical model for rolling/sliding line contacts operating in boundary and near boundary lubrication. The model is developed with first-principle formulations and incorporates key mechanical, thermal and tribochemical aspects of the problem including mode of deformation of the contact, friction, flash temperature, boundary film characterization and fluid-solid load sharing. For given load, speeds, bulk temperature and proportion of solid loadsharing, the model outputs a number of variables that are useful for the assessment of the state and severity of the problem. They include contact pressure, temperature, degree of plastic deformation, friction coefficient, friction power intensity, degree of friction-induced junction growth and integrity of the boundary film. The model may be implemented into a gear contact model to study gear systems under loss of lubrication. It may also be integrated with the light mixedlubrication model of the authors to develop a more complete mixed-lubrication model covering the entire regime of the mixed lubrication. The model is evaluated with a limited scope and more extensive evaluations are needed in time of its validity and applicability through various means and in various settings.
This paper developed a point-contact mixed lubrication (ML) model, incorporating thermal effect, the asperity elasto-plastic deformation and the boundary film properties, to evaluate the relative severity of contact condition. Then, based on the integrity of boundary films and the sharp increase of the friction coefficient, the possibility of the occurrence of scuffing was evaluated. The model was verified with published experimental data. A systematic parametric analysis was made to investigate the influences of surface roughness, contact geometry, and the lubricant properties on contact performance. The results suggest that low surface roughness and high-quality boundary film can effectively improve the scuffing resistance under current operating conditions, while high-viscosity oil and large-radius curvature are not as much effective especially when the components work under high-sliding and high–temperature conditions.
To improve the endurance and reliability of cylindrical roller bearings under complex operating conditions, a dynamic model of cylindrical roller bearing (CRB) is developed. The model incorporates roller-raceway contact model to optimize roller profile and is further verified with published data. Systematic parametric analyses are conducted to investigate the influence of flange angle, roller-end sphere radius and roller profile on load distribution, roller tilt, roller skew and contact performance. The results suggest that high flange-roller contact location and contact stiffness can effectively extend fatigue life of the bearing, while low flange-roller contact location can reduce the heat generation. In addition, roller profile has negligible effect on load distribution, but an optimized roller profile can improve the anti-tilt capacity. The developed model provides a tool for the internal design and frictional loss optimization of CRB under combined loads.
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