The continuous reduction of head–disk spacing has made the use of supersmooth media a necessity in gaining ultrahigh magnetic recording areal density. To overcome the stiction barrier associated with supersmooth disks without compromising the head flyability requirement, texture features can be transferred from the disk surface to the slider surface, creating a new type of head–disk interface, the padded slider interface. The tribology of a padded slider interface is in many ways different from that of the traditional head–disk interface with texture on the disk only. In this article, various unique tribological aspects of the padded slider interface are discussed in detail. Both theoretical modeling results and experimental data are presented to elucidate the stiction, friction, and wear behaviors of this novel head–disk interface. It is shown that the padded slider technology offers a viable alternative to the ramp load technology as a head–disk interface solution for the ultrahigh areal density.
The dynamic response of flexible beams, plates, and solids undergoing arbitrary spatial motions are systematically derived via a proposed approach. This formulation is capable of incorporating arbitrary representation of the kinematics of deformation, phenomenon of dynamic stiffening, and complete nonlinear interaction between elastic and rigid-body dynamics encountered in constrained multibody systems. It is shown that the present theory captures the phenomenon of dynamic stiffening due to the transfer of the axial and membrane forces to the bending equations of beams and plates, respectively. Examples are presented to illustrate the proposed formulations.
An ultra sensitive drive level acoustic characterization system has been developed for in-situ Head Disc Interface defectoscopy. Multimode acoustic emission (AE) sensor installed on the drive cover is designed for tracking air bearing (AB) and slider modes. Monitored modal changes at the AB and slider bandwidth correlate to the weak head disc interface (HDI) interactions such as lubricant modulation and particles induced defects. Two or three orders of magnitude increase in sensitivity can be achieved by a combination of advanced sensors, data acquisition hardware and digital signal processing algorithms. Continuous and Discrete Wavelet Transform and Joint Time-Frequency analyses are implemented for the AB modal data mining process. Performance of the newly developed technology is demonstrated on a normally operating hard disc drive (HDD).
A hard disc drive (HDD) recording head thermal protrusion is monitored by the passive acoustic characterization technique where adaptive discrete wavelet (ADW) filtering has been introduced to declare the contact. A phenomenological model is built to demonstrate detectability of the passive acoustic monitoring. The model is based on the mechanical impedance approach where impedances of head disc interface (HDI) and acoustic emission (AE) sensor are compared for matching over air bearing/head gimble assembly frequency bandwidth. A synthesized HDI response signal derived from the HDI mechanical impedance function is compared to the real AE signal obtained during the thermal protrusion based contact detection. A methodology of HDD level AE signal characterization presented in this work consists of the ADW filtering technique where the fifth order DB7 wavelet base function is used in AE signal decomposition. The signal decomposition order is selected by the AE signal entropy minimization.
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