| Budget Amount *help |
¥15,800,000 (Direct Cost: ¥15,800,000)
Fiscal Year 2004: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2003: ¥15,100,000 (Direct Cost: ¥15,100,000)
|
|---|
| Research Abstract |
1)Experimental measurement and analysis of the unstable bouncing vibration
We experimentally clarified the details of the contact bouncing vibration of two kinds of currently used flying head slider in near-contact regime by decreasing its flying height by reducing the ambient pressure. As a result, we found that the critical flying height (take-off height) can be decreased by increasing static pitch angle. This is because the adhesion force can be decreased by a decrease in contact area in which the meniscus can form. The unstable bouncing vibration is induced in such a way that the trailing edge is first attracted to the disk and thereby the friction force acting on the slider excites the bouncing vibration. The unstable vibration mode is likely to be the lower pitch mode, but theoretically is close to the anti-resonance mode of the slider-air bearing system. Unstable vibration mode is a coupled vibration between translation and pitch motion with a small phase shift and does not conta
… More
in the rolling motion.
2)Theoretical study of the bouncing vibration of a 2-DOF slider model considering the nonlinearity of air bearing stiffness
Contact characteristics between slider pad and disk with a small asperity height is first studied, including meniscus force and bulk deformation. Then we found that the contact characteristics can be modeled by the contact stiffness in bulk deformation, meniscus adhesion force, and pull-in and pull-off separations for smooth disks to be used for a high-density recording. Next, by using these contact characteristics, we analyzed the bouncing vibration of a 2-DOF slider model considering a shearing friction force of lubricant in addition to the ordinary dry friction force. The, we found that the hysteresis phenomena of the bouncing vibration, the mode of the bouncing vibration, its destabilizing process can well be estimated by this theory. From parametric study, we found that the critical flying height (take-off height) can be decreased by decreasing adhesion force, friction force, and shearing friction force of the lubricant, and increasing air bearing stiffness, particularly trailing air bearing stiffness.
3)Identification of contact force, adhesion force and damping force by means of collision motion of a spherical slider on stationary magnetic disks.
By using glass hemispherical sliders of 1 and 2 mm in radius, and magnetic disks of 0,1,2,3 nm lubricant thickness with/without UV treatment, we experimentally measured the displacement, velocity and acceleration of the slider motion by means of digital laser Doppler vibrometer, and identified the contact reacting force and adhesion force acting on the slider at the instant of separation. As a result, we found that the contact reacting force can well be predicted by Hertzian contact theory and that the dynamic adhesion force is almost equal to the static meniscus force. The adhesion force tends to decrease from the theoretical value of the meniscus force when the radius of contact increases, the separation velocity increase, and the bonded ratio increases due to UV irradiation treatment. This indicates that a meniscus bridge can hardly form in these conditions. These results can justify the fact that the adhesion force between a flying head slider and magnetic disk is caused not by Van del Waals force but by meniscus force. Less
|
