The airflow of a 10,000 rpm hard disk drive is simulated using the LES turbulent model. The critical parameters for using LES model to get the correct/reliable result are discussed. The flow induced vibration of the head gimbal assembly is calculated with the obtained fluid force acting on the head gimbal assembly (HGA) and compared with measured results. Good agreement is observed between the measured and simulated results. The optimization of the airflow is further carried out to reduce the flow induced vibration of the HGA. It is found that almost 50% reduction of flow induced vibration of the HGA can be achieved with the proposed modifications for airflow optimization.

Flow-induced vibration (FIV) of a head gimbals assembly (HGA) in hard disk drives (HDDs) limits the positioning accuracy of magnetic head in the HGA for higher HDD magnetic recording density. The pressure fluctuations characterize turbulent fluctuations exciting the HGA off-track vibration (HGA-OTV). In this paper, experimental studies have been carried out to investigate the spectrum characteristics correspondence between pressure fluctuations around an HGA and the simultaneous HGA-OTV under different HDD rotation speeds. A practical and effective experimental setup has been implemented to enable the simultaneous measurements on both the pressure fluctuation and HGA-OTV signals, where pressure fluctuations are measured with a pressure transducer through a small hole on the HDD top cover and the direct HGA-OTV signals are detected through a laser Doppler vibrometer. Results under conditions of three different HDD rotation speeds of 7200, 9000, 10800 rpm have been investigated and compared. It is shown that the HGA off-track vibration spectra are highly associated with those of the pressure fluctuations in terms of principal peaks in four frequency bands around 1.8 kHz, 2.5-3.5 kHz, 7-7.5 kHz and 11.5-12.5 kHz. With increasing HDD rotation speed, it is shown that the spectrum magnitudes of both the pressure fluctuation and the HGA off-track vibration increase correspondingly, while the principal peak positions in spectra of either pressure fluctuation or the HGA off-track vibration always hold the line. This study demonstrates a causal nexus from the pressure fluctuation to the HGA off-track vibration and suggests the feasibility of controlling the HGA-OTV through suppression of pressure fluctuations around the HGA.

A high-speed ferro-fluid bearing spindle motor for hard disk drive is introduced. Some design challenges and considerations on electrical motor, bearing system and spindle structure are addressed. The testing results of the prototypes are presented and discussed. The shown testing results of the prototypes indicate that the objective of developing a high-speed, high-performance, fluid-bearing spindle motor is fulfilled. It is a prospective spindle motor to be used in future hard disk drives.Index Terms-Design, ferro-fluid, fluid bearing, spindle motor.

The modeling for investigating the thermal effect on slider in heat assisted magnetic recording is built and its verification is conducted by comparing the simulation results and experiment results. The temperature distribution on the slider induced by locally heated media in 1Tb/in 2 is simulated and the results show that the effect is within a very small zone on the bottom surface. The temperature changes on other surfaces are less than 0.1 o C, which can be negligible.

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