THE EFFECT OF DISK WARPAGE SKEW ON THE DEFLECTION AND VIBRATION OF A FLEXIBLE DISK SPINNING ABOVE A BASEPLATE AND IN CONTACT WITH A POINT-HEAD/

A flexible disk, with small initial warpage/skew is spinning in close proximity to a stationary baseplate. The partial differential equation for the disk deflection is coupled to the Reynolds equation of the st abilizing air-film. Disk warpage/skew produces a small change in the d eflection,which rotates with the disk. These deflections are obtained by linearizing the coupled equations about the axisymmetric configurat ion corresponding to a perfect disk. Numerical solutions are obtained and compared for different values of rotational speed and air-film thi ckness. The results show that among the three skewed/warped disks mode led, the skewed disk (i.e., the plane of the disk is skewed with respe ct to its axis of rotation) produces the largest deflection change (ax ial runout). With the effect of a point-contact head included, the exi stence of disk warpage/skew causes the head to produce a spatially-fix ed harmonically varying farce. The total disk motion is determined by superposition of the deflection pattern fired on the disk and the spac e-fired head-induced vibration. The disk pitch angle variation at the head is obtained and the results are compared for various values of th e rotational speed and air-film thickness.