Guided wave mode selection for health monitoring of sub-surface hidden defects on fuel weep holes

Abstract

The in situ health monitoring of defects on the blind side of open holes using ultrasonic plate waves is a challenging problem. Scattering phenomena in this hard-to-inspect region can be used indicate the presence of the defect. This is especially advantageous if these phenomena give rise to the scattering of a wave mode that is unique to the interaction between the incident wave mode and defect. When the defect in question is located within an inaccessible structure, an understanding of how the incident ultrasonic elastic wave field can be scattered from this hidden defect propagates to the accessible surface is important. This paper presents a series of computational investigations to highlight the essential physics that explains the scattering phenomena by a defect located on the blind side of an open hole. The work presented is relevant to the monitoring of defects located in hard-to-inspect regions of future unitized metallic and composite structures. The outcomes advance the knowledge base of inspection of hard-to-access regions with actuators and sensors placed in easily accessible locations.

Scattering Phenomena of Edge Guided Waves at and around Notches

“…On further investigation Doherty and Chiu [9] found a clear generation of an SH0 mode at the tip of the notch using a scatter plot. As shown in Fig.…”

“…On progress this SH0 wave travels as an edge guided wave. This wave scatters into the medium and finally surfaces as a Rayleigh-type wave [9]. This paper will present a computational study aimed at better understanding the interaction of edge guided waves with crack tips, with a view to developing a quantitative inspection methodology suitable for crack sizing in hard-to-inspect locations.…”

Computational Study of the A0 Scattered Field Due to an Edge Delamination

“…The drawback with this traditional application of ultrasonic waves for damage detection is that it is often restricted to detecting damages in the immediate vicinity of the acoustic source and hence requires time-consuming scanning for wide-area inspection [5]. The use of Lamb waves is a widely studied alternative, which has the potential to scan entire plates and detect damage that is not in direct line of sight of the source [6]. Studies have shown great promise in the diagnostic ability of Lamb waves in detecting several types of defect: cracks, corrosion and delamination damage [7].…”