Plate damage identification using up-converted chaotic excitations

Lamb waves have been widely used as an efficient means of detecting damage in plate-like structures. Numerous signal-processing techniques are available for evaluating and processing measured Lamb waves for damage identification. In this study, we investigated the use of a novel excitation that is created by frequency up-conversion of a standard Lorenz chaotic signal into the acoustic regime. Recent research has shown that high frequency chaotic excitation and state space reconstruction may be used to identify incipient damage (loss of preload) in a bolted joint. In this study, an experiment is undertaken using an aluminum plate with an array of piezoceramic patches bonded to one side. Damage is initiated through the process of electrolytic corrosion. A novel spatio-temporal prediction error algorithm is used to determine the existence, location, and extent of damage. This paper summarizes considerations needed to design such a damage identification system, experimental procedures and results, and additional issues that can be used as a guideline for future investigation.