A comparison of embedded sensor Lamb wave ultrasonic tomography approaches for material loss detection

Computerized tomography (CT) algorithms have been used mainly in the medical field but their powerful capabilities are being exploited more and more in industrial applications. This paper demonstrates that the technology is capable of detecting material loss on real aircraft components using embedded piezoelectric sensors on hidden surfaces. The work is novel in more than one respect. Firstly, it demonstrates that Lamb wave ultrasonic tomography can be used to accurately map material loss on an exposed aircraft surface with sensors embedded on the structure's hidden surface. Hidden, in this case, refers to the surface that is not exposed to the atmosphere—the underneath of an aircraft wing, for example. Secondly, it compares tomographic images generated by fan-beam back projection and the signal difference coefficient methods, showing clearly that the latter are more sensitive to material loss.