Influence of Disk Surface Bulge and Hard Disk Operating Conditions on Hard Disk Gas Film Heat Transfer

When the hard disk is running,the cantilever of the magnetic head imposes a certain preload on the slider of the magnetic head to form a wedge space with the disk.When the disk rotates,the viscous gas enters the convergence gap so that the hydrodynamic pressure generates balance with the force acting on the cantilever,ensuring that the magnetic head flies above the disk in a stable altitude and forms a stable air film between the magnetic head and the disk called air bearing.When the flight altitude is low,the bulge on the disk surface will affect the pressure distribution of air bearing.Furthermore,the pressure affects the heat flux of air bearing by influencing the heat transfer parameters,such as thermal conductivity,dynamic viscosity,gas density,and the molecular free path of the gas.In this paper,heat transfer parameters influence on gas film heat transfer were explored.Based on this,flathead slider and Tri-pad barotropic magnetic head slider were compared,and the effects of disk operating conditions at the average temperature of air bearing were also studied,such as pitch and roll angle of the magnetic head slider,the disk s speed,and the bulge on disk surface.

Study on Lubricant Materials Transfer between Head and Disk

With the increase of hard disk storage density,the flying height of magnetic head sliders has become lower in recent years,which makes it easier for lubricant materials to transfer between the magnetic head and disk.The ability for lubricant materials to transfer is not only related to the operating conditions of disk but also related to the types of lubricant materials(Perfluoropolyether,PFPE)and diamond⁃like carbon(DLC)coating applied to the disk.Based on the principle of molecular dynamics,this study established the adsorption models on disks with different carbon content and the diffusion models of several common PFPE molecules in air.Besides,the adsorption energy and the diffusion coefficients of different models were calculated.Furthermore,the molecular weight,the molecular structure,the lubricant material􀆳s end functional groups,and the disk􀆳s carbon content were found to have influence on the transfer ability of lubricant materials.In particular,the latter two factors have further influence.