Inverse problems in structural dynamics
Abstract
Inverse problems in structural dynamics--where information about the structure is inferred from experimentally measured responses--are quite common but usually very difficult to solve. The frequency domain spectral element method is applied to a number of inverse problems in frame structures. Taking a wave propagation approach, the complicated multi-dimensional wave behavior in such structures is modeled using a collection of connected waveguides; emphasis is placed on the need for proper higher order waveguides and appropriate joint modeling. This approach is used to construct a dynamic model of the structure, from which the transfer functions relating input force and system response are obtained. These frequency-dependent transfer functions are first used to obtain force reconstructions by deconvolving the propagation behavior from experimentally measured acceleration responses. Consideration is given to aspects such as the use of multiple sensors and their location. By combining this technique with a search routine based on a stochastic genetic algorithm, an iterative method to determine the location of an unknown impacting force is also demonstrated. Finally, these techniques are used to identify the size and location of damage (due to a crack) in a frame structure. The essence of the approach is that force reconstructions obtained from the measured responses and various guessed structural models are used in an iterative search to determine the crack parameters which best represent the actual damage. In each of the crack problems considered, a number of practical issues associated with the modeling of cracks are also addressed.
Degree
Ph.D.
Advisors
Doyle, Purdue University.
Subject Area
Aerospace materials|Mechanical engineering
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