Numerical Prediction of Surface Roughness Effect on Slip Flow in Gas-Lubricated Journal Microbearings

Abstract

Development of micro rotating devices in microelectromechanical (MEMS) has introduced a kind of ultrashort self-acting gas-lubricated journal microbearing with small length-to-diameter ratios. A mathematical model for the slip flow in an ultra-thin-film gas-lubricated microbearing is developed with surface roughness effect. The random surface roughness characterized by fractal geometry and described with a Weierstrass-Mandelbrot (W-M) function is applied to represent the roughness of the bearing surface. A modified Reynolds equation considering a velocity slip boundary condition is derived. Numerical simulations are obtained for the microbearing under effects of rarefaction and roughness. The results indicate that roughness has a more significant effect on the properties of the gas-lubricated journal microbearings for MEMS applications.

KEY WORDS:

• MEMS
• Load-Carrying Capacity
• Journal Bearing
• Surface Roughness
• Slip Flow
• Fractal Surface Topography

ACKNOWLEDGEMENTS

This work was supported by the National Science Foundation of China under Grant No. 11072147, the National Outstanding Youth Foundation of China under Grant No.10325209, and the Specialized Research Fund for State Key Laboratory of Mechanical System and Vibration under Grant No. MSVMS201106. This work was sponsored by the Shanghai Rising-Star Program under Grant No. 11QA1403400.

Review led by Michael Khonsari