Novel Microwave Method for Detection of Finite Surface Cracks in Metals


An electromagnetic model for finite surface crack detection is presented. An open-ended waveguide sensor is used to scan a cracked metal surface. The crack is modelled as a large waveguide feeding a smaller one. The characteristics of the standing wave set up in the waveguide is altered when the waveguide is terminated by an imperfect short circuit load (crack surface). This is due to the generation of higher order modes as a result of the presence of the crack. Strategic probing of the standing wave properties is used to indicate the presence of a crack. A Fourier boundary matching technique is used to satisfy the boundary conditions at the waveguide aperture and the crack boundaries. The behavior of crack characteristic signals as a function of crack size and location within the sensor aperture is also studied. A finite fatigue crack is finally detected at 38 GHz to demonstrate the practical feasibility of this technique.

Meeting Name

Advanced Microwave and Millimeter-Wave Detectors (1994: Jul. 25-26, San Diego, CA)


Electrical and Computer Engineering

Keywords and Phrases

Boundary Conditions; Cracks; Fourier Transforms; Metals; Sensors; Surfaces; Waveguides; Electromagnetic Models; Standing Waves; Microwave Devices

International Standard Book Number (ISBN)


International Standard Serial Number (ISSN)


Document Type

Article - Conference proceedings

Document Version


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© 1994 SPIE--The International Society for Optical Engineering, All rights reserved.

Publication Date

01 Jul 1994