Collaborative Research: Three-dimensional Continuously Scanning Laser Vibrometry with Application to Structural Damage Detection

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The laser vibrometer is a state-of-art-art instrument used to characterize vibration of a structure. This information is important to evaluate the correctness of design of structures that routinely experience vibration; to identify areas of concern for maintenance and repairs of those structures before failure occurs; and to pinpoint the location and mode of failure of the structures, if pre-failure remediation is not undertaken or is insufficient. This technique, however, is very tedious and time-consuming for measurement of structures with complex configurations. These may include large structures subject, for example, to ongoing loading from wind, or flowing water, or the steady flow of traffic. This project aims to develop a continuously scanning laser vibrometry method for accurate and rapid characterization of vibrations of structures with complex configurations. The ultimate application of this research will advance the national prosperity and defense by providing early warnings of the need for maintenance and repair of structures, or of the onset of failures of critical structures. This can reduce potential economic and human losses, in addition to advancing knowledge in the field of measurement science. Outcomes of this project will also be demonstrated to underserved high school students in a summer educational program to spark their interest in science and engineering.Overarching objectives of this project are to investigate full-field three-dimensional continuously scanning laser vibrometry and apply it to non-model-based structural damage detection. Laser vibrometry can measure three-dimensional vibrations of structures with curved surfaces and time-varying positions and orientations, and estimate their vibration shapes that can be used for damage detection when structures are under ambient excitation. Scan trajectories of three laser spots need to be synchronized, which requires derivation of kinematic relations between a prescribed scan trajectory and each laser spot. Non-image-based and image-based methods will be developed to obtain them. New output-only vibration shape measurement methods will be developed for structures under ambient excitation. A robust and efficient non-model-based damage detection method that uses different types of vibration shapes measured by laser vibrometry will be developed. The damage detection method is robust, practical and versatile, and does not require any baseline information of structures, such as their dimensions and boundary conditions, and vibration shapes of corresponding undamaged structures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.