Perpendicular Magnetic Recording Media on Various Hard-Disk Substrates
Co-Cr perpendicular media on rigid substrates were studied. We used untextured glass substrates for perpendicular magnetic hard disks, but the reproduced output at short wavelengths was influenced by the surface roughness of the magnetic recording media. We therefore fabricated Co-Cr perpendicular hard disk media deposited onto different substrates: untextured glass, silicon single crystal, chemically textured alumite, and Mn-Zn ferrite. We compared these substrates with respect to their crystallographic properties, head-to-medium spacing, and record/playback characteristics.
MAGNETIC AND TRIBOLOGICAL PROPERTIES OF CO-PT MAGNETIC FILMS ON CHEMICALLY TEXTURED AL RIGID DISC SUBSTRATES
-For high density recording, it is very important to reduce the spacing between the magnetic head and the disc, avoiding the higher risk of the head stiction and crash with the reduced spacing. This report summarizes the new DOUBLE CTX (Chemical Texturing) system for low temperature magnetic layer production. The DOUBLE CTX was found to provide excellent texture for sputtered Co-Pt of 1400 Oe at 500 C, due to no projection of the head hit at a flying height of 0.1 J.!m and 30000 CSS materialized with no increase in friction coefficient. The magnetic measurement showed that Hc.increased with the increasing depth of texturing (etching depth). Although the chemical texturing was isotropic on the disc surface, output modulation caused by the inline sputtering was not observed. It is confirmed that the chemical texturing is effective in achieving reliable sputtered rigid discs with low flyability and excellent recording characteristics.
Numerical analysis of surface crack propagation in flexible pavements using XFEM and cohesive zone model
Surface initiated (top-down) cracking in the longitudinal direction of pavements has become a predominant mode of failure in thick asphalt pavements. Most previous researchers studied crack propagation using the traditional Linear Elastic Fracture Mechanics (LEFM) method by calculating the stress intensity factor around the crack tip. In this paper, Extended Finite Element Method (XFEM) was used to study the key factors causing surface initiated crack propagation under surface tension and/or shear. A two-dimensional (2-D) finite element (FE) model for a two-lane flexible pavement was built to predict pavement responses and crack propagation potential under various scenarios. It was found that surface tension is the major driving force for crack propagation when the crack is at some distance away from tire loading. The results show that the distance from the location of crack to tire loading, the depth and direction of the crack, and the modulus ratio between the hot-mix asphalt (HMA) layer and the base layer have significant influences on crack propagation under surface tension. On the other hand, this study shows that shear stress can induce surface initiated crack propagation near the loading area as the shear resistance of material becomes low at the high temperature.