A Numerical Analysis On Performance Of Hybrid Bearings Considering Surface Roughness

Hybrid bearings, as critical support units, are widely applied in various high-speed, highprecision and large-load CNC due to their great stiffness, load-capacity and low friction. So far, many papers studying the structural design and dynamic mechanisms of hybrid bearings have been published. However, effects of several unnoticeable factors, like surface roughness, on the performances of hybrid bearings do not receive enough attentions. Therefore, considering the effects of Gaussian and Non-Gaussian distributed rough surface, this article has investigated the hybrid bearings’ working performancesThis article has presented the source of project, analyzed the research background and significance, reviewed the domestic and overseas current situations about studying orificecompensated hybrid bearings and rough surface and finally pointed out several existing problems, like the unavailability of roughness analysis in commercial software.The method to study the rough surface has been introduced, including the Christensen model and a more widely-used model, average flow model. After that, the finite element method has been explained how to solve the model numerically. A comparison between results from this article and these from international paper has been presented to show accuracy.Based on the methods introduced previously, this article analyzes the influence of Gaussian distributed rough surface on the minimum film height, flow, stiffness, damping and threshold speeding of orifice-compensated hybrid bearings. Results shows that different rough surface has different effects and effects will be more significant with larger asperity heights.Since the physical surfaces after processing show pronounced Non-Gaussian distribution, the Edgeworth-series including skewness and kurtosis has been introduced to describe the characteristics. The model has been modified and relevant analysis has been conducted.Finally, a case has been presented to show how to design a hybrid bearing for a highspeed grinding machine tool considering the surface roughness. It also explains how to apply the widely-used parameter, average roughness(Ra), into the theoretical model. Then three design suggestions have been provided.