Analytical and Numerical Investigation of Structural Damage Detection and High-Dimensional Dynamic Response of Nonlinear and Time-Varying Systems

Title	Analytical and Numerical Investigation of Structural Damage Detection and High-Dimensional Dynamic Response of Nonlinear and Time-Varying Systems
Author	Xu, Guangyao
Advisors	Zhu, Weidong
Program	Engineering, Mechanical
UMBC Department	Mechanical Engineering
Document Type	dissertation
Sponsors	University of Maryland, Baltimore County (UMBC)
Keywords	Damage Detection; Distributed Structural System; Nonlinear and Time-Varying System; Incremental Harmonic Balance Method; Ill-conditioned System equations; Enrich Measurement Information by Modifying Tested Structure in a Controlled Manner; Engineering, Mechanical (0548); Engineering, Civil (0543); Engineering, Industrial (0546)
Date Issued	2007-11-26; *
Abstract	This dissertation is concerned with two challenging areas of vibrations research: 1) inverse modeling for vibration-based structural damage detection, and 2) high-dimensional dynamic response of nonlinear and time-varying distributed structures. In the first area, we address structural damage detection using changes of natural frequencies, treatment of non-uniqueness of solutions, and treatment of ill-conditioned systems. A robust iterative algorithm is developed and applied to identify the locations and extent of damage in slender structures using only the changes in their first several natural frequencies. The algorithm, which combines a first-order, multiple-parameter perturbation method and the generalized inverse method, is tested extensively through experimental and numerical means on cantilever beams with different damage scenarios. A new method is developed to enrich the measurement information by modifying the structure in a controlled manner. A new method using singular value decomposition is developed to handle the ill-conditioned system equations when they occur. In the second area, we consider the high-dimensional, nonlinear and time-varying dynamic response of distributed systems with small bending stiffness, such as elevator cables and memory tapes. The effects of bending stiffness, different trial functions, number of trial functions used, and boundary conditions on the dynamics characteristics of cables with small bending stiffness are investigated. Furthermore, a nonlinear model of a friction-guided translating beam with a stationary load system, a boundary excitation, and a periodically varying transport speed is developed. The Incremental Harmonic Balance (IHB) method is extended for the first time on high-dimensional models of a distributed structural system. It is demonstrated that this method can successfully handle a variety of problems, including linear and nonlinear frequency response analyses, system optimization, determination of parametric instability region boundaries, determination of periodic responses for parametrically-excited nonlinear systems, and determination of periodic responses of linear and nonlinear systems under combined parametric and forced excitations. For the distributed system considered here, results show that a large number of trial functions in the spatial discretization are often required to yield the converged solutions; in addition to quantitative inaccuracy, low-dimensional models of the distributed system can lead to qualitatively misleading predictions.
Identifier	1097
Format	application:pdf
Language	en
Collection	UMBC Theses and Dissertations
Rights Statement	This item may be protected under Title 17 of the U.S. Copyright Law. It is made available by UMBC for non-commercial research and education. For permission to publish or reproduce, please see http://aok.lib.umbc.edu/specoll/repro.php or contact Special Collections at speccoll(at)umbc.edu.

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Analytical and Numerical Investigation of Structural Damage Detection and High-Dimensional Dynamic Response of Nonlinear and Time-Varying Systems

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