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Time-frequency analysis of systems with changing dynamic properties

Citation

Bradford, Samuel Case (2007) Time-frequency analysis of systems with changing dynamic properties. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-11292006-214839

Abstract

The Wigner-Ville Distribution, and related refinements, represent a class of advanced time-frequency analysis tools that are distinguished from Fourier and wavelet methods by an increase in resolution in the time frequency plane. Time-frequency analysis provides a set of exploratory tools for analyzing changing frequency content in a signal, which can then be correlated with damage patterns in a structure.

For systems of interest to engineers, investigating the changing properties of a system is typically performed by analyzing vibration data from the system, rather than direct inspection of each component. Nonlinear elastic behavior in the force-displacement relationship can decrease the apparent natural frequencies of the system - these changes typically occur over fractions of a second in moderate to strong excitation and the system gradually recovers to pre-event levels. Structures can also suffer permanent damage (e.g., plastic deformation or fracture), permanently decreasing the observed natural frequencies as the system loses stiffness. Advanced time-frequency representations provide a set of exploratory tools for analyzing changing frequency content in a signal, which can then be correlated with damage patterns in a structure. Modern building instrumentation allows for an unprecedented investigation into the changing dynamic properties of structures: a framework for using time-frequency analysis methods for instantaneous system identification is discussed.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:damage detection; Millikan Library; spectrogram; structural health monitoring; wavelets; Wigner-Ville Distribution
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Civil Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Heaton, Thomas H.
Thesis Committee:
  • Hall, John F. (chair)
  • Beck, James L.
  • Kohler, Monica D.
  • Clayton, Robert W.
  • Heaton, Thomas H.
Defense Date:19 July 2006
Record Number:CaltechETD:etd-11292006-214839
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-11292006-214839
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4689
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:01 Dec 2006
Last Modified:26 Dec 2012 03:11

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