J. Q. Mou

Shock analysis of MEMS actuator integrated with HGA for operational and non-operational HDD

In this paper, the effects of shock on MEMS microactuator integrated with Head Gimbal Assembly (HGA) for operational and non-operational HDD are studied. ANSYS/LS-DYNA is used for the finite element modeling and simulation. Shock responses are investigated at the height with the shock amplitude of 1000g and within the shock duration of 1ms. The preloaded state of the suspension is considered for the simulations. The operational HDD model uses linear springs to represent the air bearing stiffness of the head disk interface. The maximum stress is located at the corner of the flexure beam and center portion. A larger maximum stress is found for the nonoperational HDD model compared to the operational HDD model. This is due to the strong air bearing forces limiting slider motion.

Flow-Induced Slider Vibration in a Functional Hard Disk Drive: Influence of Air Shroud

An air shroud is designed and placed within a commercially available hard disk drive operating at 15 000 rpm. Large eddy simulations of the turbulent airflow characteristics resulting from both the models, with and without air shroud, are carried out by assuming the read/write head is at the disk middle diameter. The numerical model consists of about nine million tetrahedral cells with the largest and smallest sizes of the cell volumes being 2.5 mm3 and 0.35 mm3 , respectively. The dynamic Smagorinsky-Lily model is employed to mimic the effect of small-scale eddies in the turbulent airflow. Numerically predicted airflow characteristics are compared against the LDA measurements and found to be in good agreement. The wind blowing on the surfaces of the head gimbals assembly is converted into aerodynamic forces and the resulting slider displacement in the off-track and out-of-plane directions are investigated. It is inferred that the disk drive model with air shroud results in a maximum of 44% and 10% less off-track and out-of-plane slider displacements, respectively.

Analysis of structurally transmitted vibration of HDD in notebook computer

Characteristics of structurally transmitted hard disk drive (HDD) vibrations induced by different built-in vibration sources, including speakers, fans and a CD/DVD drive in a notebook PC, are examined. It is found that at the high frequencies above 1000 Hz, the structurally transmitted HDD out-of-plane vibration is dominated by the vibrations induced by the speakers. The effects of the chassis design and HDD mounting on vibration transmission from speakers to HDD via chassis in the notebook PC are investigated. It is concluded that, in general, softer chassis and softer HDD mounting is helpful in suppressing the structurally transmitted vibrations of HDD at frequencies above 1000 Hz in a notebook PC. Furthermore, the HDD softer mounting modes should be kept away from the low order harmonics of the built-in fans and CD/DVD drive.

Three dimensional finite element model for transient temperature prediction in hard disk drive

Hard disk drive (HDD) is often subjected to transient temperature during frequent seeking or due to the change of environmental conditions that causes HDD reliability problems. This paper presents a three dimensional (3D) finite element modelling technique that can be used to predict the transient temperatures of the HDD when it subjected to transient temperature during frequent seeking or due to the change of environmental conditions.

Analysis of Built-in Speaker-Induced Structural-Acoustic Vibration of Hard Disk Drives in Notebook PCs

This study is to develop a methodology and model to analyze the built-in speakers induced structural acoustic vibration of hard disk drive (HDD) in Notebook PC. First, a structural finite element (FE) model is built for the notebook PC to be analyzed using ANSYS. This FE model is subsequently verified by experiments. Second, the effects of acoustically transmitted and structurally transmitted oscillating forces, induced by the speakers, acting on the HDD, are investigated by acoustic FE model (SYSNOISE) and structural FE model. The acoustic transmission effect on the vibration of HDD is also investigated by experiment, which shows that the simulation results have a good agreement with experimental results. Finally, the effects of stiffness and damping ratio of the HDD supporters on the vibration of HDD are analyzed by the verified FE model.

Reduction of Flow Induced Vibration in Hard Disk Drive

In this paper, system level analysis is carried out for a functional HDD with two disks and four sliders operating at spindle speed of 15000 rpm. Full numerical models both for computational fluid dynamics (CFD) analysis and structural Finite Element Analysis (FEA) are developed. The flow induced vibrations of the sliders in all three directions, namely, off-track (X), down-track (Y) and out-of-plane direction (Z) are examined respectively. The numerical simulation results are compared and validated with the experimental results measured with a 3D laser Doppler vibrometer (LDV). Good agreements are observed for the vibrations in the three directions. The airflow patterns and characteristics of the flow induced vibration in HDD for three critical positions of the head gimbal assembly (HGA) parked at the disks identified as ID, MD and OD are investigated. The results reveal that the first slider from top has the highest flow induced vibrations in all the three directions due to the higher turbulent flow close to the top disk surface. Moreover, the results indicate that the slider vibration is interacted with the disk flutter in the HDD. Optimal designs of the HDD disk and air shroud are carried out to reduce the flow induced vibration of the slider, by suppressing the disk flutter and improving the turbulent flow in the HDD. It is demonstrated that significant reduction of flow induced slider vibration could be achieved with the optimal designs of the HDD.Copyright

Thermal stability modeling and evaluation of piggy-back microactuator for hard disk drives

In this paper, the thermal stability of a piggyback electrostatic microactuator integrated with head gimbal assembly (HGA) for hard disk drives (HDD) is modeled and evaluated. Firstly, the temperature stability of the microactuator in terms of dimensions is analyzed. Different microstructure materials, such as nickel, Invar, and single crystal silicon, fabricated by LIGA and LISA processes separately, are evaluated based on the finite element model. Then, the thermal deformation and thermal stress of the microactuator are simulated for two schemes of die-attach HGA integration. Lastly, the variance in operational characteristics of the microactuator caused by the thermal deformation is analyzed by electrical-mechanical couple analysis. The evaluation results demonstrate that the single crystal silicon microactuator with the four spot die-attach HGA integration has better thermal stability in operational performance.

Modeling and prediction of structure-borne seek noise of HDDs

A numerical approach is presented for predicting the structure-borne seek noise in hard disk drives (HDDs) in time-domain. Rayleigh integral is adopted to relate the transient acceleration of top cover to its radiated sound pressure. A finite element modeling and simulation technique is employed to arrive at the transient vibration response, which is further used as the input for acoustic noise level calculation. The prediction results of a 1.8” HDD reveal the high dependency of structure-borne seek noise level on the current profile applied to VCM.

Investigation of Soft Failure of Small Form Factor HDD under Forced Vibration

As small form factor hard disk drives (HDD) are increasingly used in portable consumer devices, the performance of the HDD in daily activity is highly concerned. In this paper, the soft failure of the hard disk drive under forced vibration is investigated. To investigate the cause of the soft failure, experimental frequency analysis was conducted. Modal analysis of HDD was completed by experiment and verified by FEM simulations and the result was compared to the frequency response result. Studies show that the vibration modes of head suspension assembly (HSA) and disk platter at higher resonant frequencies do not directly related to the soft failure