NEW METHODS IN MODAL ANALYSIS AND STRUCTURAL DAMAGE IDENTIFICATION
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Date
2017-01-01
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Mechanical Engineering
Program
Engineering, Mechanical
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Distribution Rights granted to UMBC by the author.
Distribution Rights granted to UMBC by the author.
Abstract
Modal analysis is a subject of structural dynamics, as it describes properties of a linear structure in the modal space with modal properties, including natural frequencies, modal damping ratios, and mode shapes. With the development of transducer and computer technologies, accuracy and efficiency of modal property evaluation have been drastically boosted in the past few decays. As modal properties of a structure are directly related to its structural properties, such as mass, damping, and stiffness, measured modal properties can be processed to identify structural damage. In this dissertations, new methods in modal analysis and structural damage identification are developed and investigated. In the area of modal analysis, two modal testing methods and two digital signal processing methods for modal analysis are proposed for accurate and efficient modal property evaluation. Specifically, an operational modal analysis method that uses non-contact excitation and measurement to measure out-of-plane and in-plane vibration modes of a plate and a vibro-acoustic modal test method that uses sound pressure transducers at fixed locations and an impact hammer roving over a test structure are studied; a digital signal processing method for calculating correlation functions and power spectra and one for calculating impulse response functions and frequency response functions are studied. In the area of structural damage identification, two methods for beam structures and two methods for plate structures are proposed without use of models of associated undamaged structures. Specifically, a method using curvature mode shapes of beams and a method using continuous wavelet transforms of mode shapes are studied; a method using mode shapes of plates and one using various curvature mode shapes are studied. In addition, a structural damage identification method that uses free response shapes of beam structures by use of a continuously scanning laser Doppler vibrometer system is proposed. The above mentioned methods are numerically verified and experimentally validated.