Discoveries in using open ended rectangular waveguides for microwave surface crack detection and sizing have generated interest. The foundation, potential, advantages and disadvantages of this methodology, developed at the Applied Microwave Nondestructive Testing Laboratory in the Electrical Engineering Department at Colorado State University, are discussed. Microwave techniques in general and this particular approach offer certain unique advantages that can advance the state of the art of fatigue/surface crack detection. The basic features and capabilities of this technique have been theoretically and experimentally investigated these past few years. However, more developmental work is needed to bring this technique from the laboratory to the real testing environment. The microwave method described has proven to be very effective in detecting and characterizing surface cracks in metals. It is inexpensive and can readily be applied in various environments. This approach applies to exposed, empty, filled and covered cracks. Cracks may also be detected remotely (i.e. the use on a liftoff in between the waveguide aperture and the surface under examination).


Electrical and Computer Engineering


United States. Federal Highway Administration

Keywords and Phrases

Applied Microwave Nondestructive Testing Laboratory; Colorado State University; NDT; Covered Cracks; Crack Detection; Crazing; Empty Cracks; Exposed Cracks; Fatigue Crack Detection; Fatigue/Surface Crack Detection; Filled Cracks; Metals; Microwave Measurement; Microwave Method; Microwave Surface Crack Detection; Microwave Surface Crack Sizing; Microwave Techniques; Nondestructive Testing; Open Ended Rectangular Waveguides; Rectangular Waveguides; Stress Analysis; Stress Crack Detection; Testing Environment; Waveguide Aperture

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





© 1996 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Oct 1996