Theory And Applications Of Nano Scale Thin Gas Film Lubrication

Thin gas film lubrication theory and technology at nano scale , which is atthe frontier of nanotribology, has prosperous potential to be applied in theinterface technology of head/disk systems in computer hard disk drives andnano/microelectromechanical systems. To explore the thin gas film lubrication theory, this dissertation studiedfirstly the differences of gas molecules micro behavior and gas transportphenomena between nanoscale and microscale. The nanoscale effect function,which describes mathematically the influences on gas flow due to scalechanging from micro to nano, was proposed in present dissertation. Thefamous Bhatnagar-Gross –Krook(BGK) collision model in nonequilibriumstatistical mechanics was modified by adopting this function and nano gaskinetic theory was well developed. Based on the above modified theory, two types of thin gas film lubricationmodels were studied. One is fully started from Boltzmann theory: the flowvelocity profile in film thickness direction, the flow rate, the shear stress andother flow coefficients in the Poiseuille flow and Couette flow at nanoclearance was calculated exactly, and then the F-K lubrication model based onBoltzmann equation was proposed. On the other part, the slip flow problem atnano scale was comprehensively investigated by using the modified BGKcollision model, a more exact formula for calculating the slip length includingthe case of surface accommodation coefficient was given, and the newlubrication model, which is relatively easy-computing, was proposed based onboundary velocity slip theory. Another work of this dissertation is on the simulation technique of theflying head in hard disk drives. The simulation for slider with complex rail onthe air bearing surface in hard disk drives was achieved by adopting thepresent lubrication model in this dissertation and using modern numerical ? II ?文摘,目录methods. The numerical result shows that the lubrication characters given bypresent model were superior to the ones of other former models. It indicatesthat the fruit of the theory and application research in this dissertation could bewidely used in future interface technology in hard disk drives and N/MEMS.