A novel microwave technique for detecting long surface cracks in metals is described. This technique utilizes an open-ended waveguide to probe the surface of a metal. In the absence of a crack the metal surface is seen as a relatively good short-circuit load. However, in the presence of a crack higher order modes are generated which in turn change the reflection properties at the waveguide aperture. This change brings about a perturbation in the standing wave characteristics which is then probed by a diode detector. The experimental and theoretical foundations of this technique are given, along with several examples. It is shown that cracks a fraction of a millimeter in width are easily detected at around 20 GHz or lower. Smaller cracks can be detected at higher microwave frequencies.


Electrical and Computer Engineering

Keywords and Phrases

20 GHz; Crack Detection; Fatigue Cracks; Fatigue Testing; Long Surface Cracks; Metal Fatigue; Metals; Microwave Measurement; Open-Ended Waveguide; Perturbation; Rectangular Waveguides; Reflection Properties; Standing Wave Characteristics; Electromagnetic Formulation-Probe Development and Antennas; Surface Crack Detection and Evaluation

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





© 1994 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Oct 1994