Detecting stress and fatigue cracks

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).