Large Area Inspection of Aircraft Structures Using Vibrational Nondestructive Evaluation Methods

摘要

The research work performed on the development of vibrational nondestructive evaluation methods to infer damage over a large area of aircraft structures using laser Doppler Velocimeter accompanied with data fusion techniques is documented. The Vibrational methods rely on the response characteristics before and after damage. Damage is reflected in changes in the vibrational characteristics which are used to quantify modal strain energy differences between the structure in the damaged and healthy states. These differences provide features that can be used to localize an quantify the damage. The collection set of modal strain energy differences for the available modes are combined using averaging and data fusion techniques to provide damage indicators. The Vibrational and fusion methodologies were developed and refined considering as series of controlled damage experiments on simple beams, a stiffened plate panel, a vertical stabilizer assembly, and a stiffened shell specimen. Modal vibration tests were conducted on these test objects using conventional accelerometers and/or a laser Doppler Velocimeter to obtain their dynamic characteristics before and after inflicted on controlled damage. Damage evaluation results are documented for each case in this report. The methods developed seem to have a major potential to detect defects that cause a stiffness change in hidden members or members deep inside aircraft structures without disassembly.