A New Method of Notching in Vibration Control
No Thumbnail Available
Date
2007-10
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
The traditional vibration test methodology of controlling the interface environment only to a
motion based specification is often too conservative, inducing potentially excessive vibration
responses at hardware resonant frequencies. This over testing problem occurs because the
smooth, input acceleration specification used in the test configuration is characteristic of a rigid,
infinite impedance equipment mount; and not characteristic of the compliant, finite impedance
equipment mount more typical of the service configuration. Recently, the so called Force Limited
Vibration (FLV) testing developed at the Jet Propulsion Laboratory offers many opportunities to
decrease the over testing problem associated with traditional vibration testing. FLV testing
methodology, controls the input acceleration and limits the reaction forces between the test item
and the shaker through real-time notching of the input acceleration, is often hard subject to apply
the force gauges. This problem has been recognized in this work and the energy limiting
vibration test methodology has recently emerged as a viable solution which makes use of stress
feedback signal to the vibration control loop using strain gauges that are trouble-free to the
functions they are meant to perform. The underlying theoretical basis of the energy limiting
vibration testing technique is the strain energy value which is the integration of product of vonmises
stress and strain over an element is a parameter prime important since it is related to the
total amount of energy transmitted to the test item during the vibration. To illustrate this
methodology, a case study of a typical satellite presented to prove the effectiveness. A procedure
was proposed to identify the topological location of notch channels or critical locations using
FEM results of the base excitation, so as to enable the vibration control mechanism to adjust the
power input of shaker table. The base excited dynamic response analysis yielded the percentage
reduction of shaker power. The notching of the force limiting and energy limiting vibration
testing methods were compared and founded incomparable even though it is acceptable.
Description
Keywords
Applied Mechanics stream