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Use of Periodically Layered Composites As a Mechanical Notch Filter to Isolate Selected High Frequency Vibrations in Data Recording Disk Files

IP.com Disclosure Number: IPCOM000061810D
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Javid, AE: AUTHOR

Abstract

In order to improve the track misregistration values of data recording disk files, it is necessary to effectively isolate sources of vibration, such as those which occur between the actuator assembly for moving the read/write transducers and the base plate for the drive motor for rotating the recording disks. A periodically layered stack of alternating materials which have wide differences in density and stiffness are located between the actuator mount and the base plate. Such periodic layers create a large impedance mismatch. Large differences in impedance result in rapid attenuation of an input wave for certain frequency ranges. This results in a mechanical filter which acts only in a specific frequency band to reduce the vibratory energy of the narrow band excitation.

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Use of Periodically Layered Composites As a Mechanical Notch Filter to Isolate Selected High Frequency Vibrations in Data Recording Disk Files

In order to improve the track misregistration values of data recording disk files, it is necessary to effectively isolate sources of vibration, such as those which occur between the actuator assembly for moving the read/write transducers and the base plate for the drive motor for rotating the recording disks. A periodically layered stack of alternating materials which have wide differences in density and stiffness are located between the actuator mount and the base plate. Such periodic layers create a large impedance mismatch. Large differences in impedance result in rapid attenuation of an input wave for certain frequency ranges. This results in a mechanical filter which acts only in a specific frequency band to reduce the vibratory energy of the narrow band excitation. At other frequencies, the composite structure will transmit the vibratory energy unmodified, thus acting as a mechanical notch filter. The theoretical development of the mechanical notch filter is based on the theory of waves in periodically layered media. The Floquet theory is used to solve the equations for the propagation of plane waves through a laminated system of parallel plates of different materials when the direction of propagation is normal to the plates.

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