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Abstract
Sources of excitation for head and lens suspension spring vibration in direct access storage devices (DASD) include disk vibration and air flow induced by disk rotation. Disk vibration is observed experimentally using laser Doppler vibrometry (LDV) to be coupled with the flow induced by disk rotation. The effect of changing design parameters on the tangential flow profile between a pair of corotating disks is studied. Mean and (rms) velocity measurements are taken using a hot-wire probe at the tip of an obstruction, in order to investigate the flow prevalent at the location of the head/arm assembly in DASD.
The maximum damping capacity for an objective lens suspension partially covered on one side with a constrained layer damper (CLD) is determined numerically as a function of coverage amount, placement location, and damping layer modulus. An inverse relationship between optimum viscoelastic modulus and associated maximum damping factor is observed and discussed. Two lens suspension designs are compared on the basis of frequency response.
It is shown that an advantageous compromise is possible between the shear surface damping behavior of a CLD and its behavior as a tuned damper. Specifically, a damping patch is shown to behave as a CLD for the bending modes of a tapered cantilevered plate, while behaving as a tuned damper for the sway modes. This dual nature leads to higher damping capacity for the sway modes than would be otherwise possible using a similar coverage of conventional CLD, at the expense of optimum CLD performance in bending. Frequency dependence of loss factors, determined using modal analysis of measured mobility frequency response functions, is compared with predictions from CLD theory and tuned damper theory. Plate response is measured using LDV for out-of-plane motion, and laser Doppler anemometry (LDA) for in-plane motion, while force excitation is measured with a piezoelectric transducer. A p-type finite element code, in conjunction with the modal strain energy method, is used to perform a normal modes and damping analysis for comparison with experimental results.
