Analysis Of Static Characteristics Of Hard Disk Lubrication System And Experimental Study Of Head Taking Off/Touching Down

Hard disk drives (HDDs) are the main storage component of the computer. They become smaller in size, higher in capacity with the development of science. In order to improve the capacity of the HDDS, the distance between the slider and the disk is called flying height which has been reduced to several nanometers. The conventional lubrication theory cannot be applied to these kind of bearing in this case. We must take consider the impact of rarefaction effects.To ensure the simulation accuracy of the static characteristics of gas film lubrication, based on the continuous fluid, this paper modifies the Reynolds equation of compressible gas considering the rarefaction. Select the new modified model — LFR model to established mathematical model. Numerical results show that LFR model has higher accuracy and higher computational efficiency.LSFD method and FV method are used to solve to the modified gas film lubrication equation. Compared the simulation accuracy and the calculation efficiency of LSFD method with FV method, we obtain that the FV method not only has higher accuracy and calculation efficiency. We use the FV method to solve the changes of head flight parameters and the pressure center. The results show that the minimum flying height and pitch angle decrease with the increase of the air bearing carrying capacities and the two parameters have obvious effects on the carrying capacities. The variation of the minimum flying height has different effects on the pressure center along X and Y direction, that is, effects on the pressure center along X direction are more obvious. The increase of pitch angle result in the pressure center increase along X direction, and the pressure center increase along Y direction decrease first and then increase. In addition, the variation range along X direction is more obvious.Based on the modified two-dimensional Reynolds equation, we introduced pressure flow factor and shear flow factor in consideration of the effects of rarefied coefficient and roughness by LFR model. It is solved by finite volume method. Effects of two-dimensional roughness mode on static characteristics of hard disk of gas film lubrication system are investigated. Numerical results show that:when the direction of roughness is along the length direction, the effect of the roughness on pressure distribution is also along the length direction in the slider; when the direction of roughness is along the width direction, the effect of he roughness on pressure distribution is also along the length direction in the slider. when the direction of roughness is along the length direction, the load carrying capacity increases with increases of the roughness, when the direction of roughness is along the width direction, the load carrying capacity decreases with increases of the roughness. The more obvious the roughness mode presents, the greater influence will emerge to pressure center. But the effect on X direction pressure center is greater than on Y direction pressure center. With the increase of the disk’s rotating speed, load carrying capacities will increase, while, slider contact will happen when the rotating speed of the disk is too low.Environmental pressure and the rotational speed of the disk influence the taking off process of the head. Analysis of the two factors are executed by HDF—TESTER (Hard disk fly—tester). Firstly, effects of the different of the disk’s speed on the slider’s taking off/touching down with different are environmental pressure analyzed. The experimental results show that, the minimum touching down speed of the head doesn’t change with the variation of the environmental pressure. The minimum taking off speed of the head increases with the decrease of the environmental pressure. Then, effects of different environmental pressure on the taking off/touching down of the head with different disk’s speed are analyzed. The experimental results show that, with the increase of rotating speed of the disk, the pressure increase first and then decrease when the head touches down and the pressure decrease continually when the head takes off. In addition, when the rotating speed is too low, rowing plate time of the head will increase, and in turn, lead to the damage of the head.