Ultrasonic tomographic reconstruction for damage detection in aluminium and glare plate-like structures

With the development of new technology, structural health monitoring offers the prospect of a quantum gain in performance and efficiency for the structural integrity management of expensive assets such as aircraft and infrastructure. For plate-like structural components, Lamb waves have been shown to provide an attractive alternative to conventional ultrasonic testing using bulk waves, particularly from the viewpoint of automated wide-area scanning, namely, tomographic reconstruction. The technique is a well-established imaging tool in the Medical and Geological field, used for scanning purposes to detect fractures, tumours or general health monitoring of health patients in the former, and to image subsurface structures for development of oil and mineral deposits in the latter. To this end, several researchers in structural mechanics have attempted to implement tomographic reconstruction techniques for in-situ detection of manufacturing defects or service-induced damage, which can provide a practical basis for structural health monitoring. These studies have resulted in correspondingly varying levels of success. The proposed work builds on these studies concentrating on the use of Lamb waves tomographic reconstruction to detect damage in plate-like structures. In this regard, three damage types are studied, namely, delamination in hybrid materials such as Glare, corrosion and through-hole damage in aluminium plate-like structures. The reconstructed images are produced using Simultaneous Iterative Reconstructive Technique (SIRT). The results of the study demonstrate how the change in the time-of-travel properties of Lamb waves can be used to detect various damage types and geometries, and how these changes affect the image quality and definition.