Abstract
Evaluation and non-destructive identification of stress-induced cracks or failures in metals is a vital problem in many sensitive environments, including transportation (steel railway tracks, bridges, car wheels, etc.), power plants (steam generator tubing, etc.) and aerospace transportation (landing gear, aircraft fuselages, etc.). There are many traditional non-destructive detection and evaluation techniques; recently, near-field millimeter waves and microwave methods have shown incredible promise for augmenting currently available non-destructive techniques. This article serves as a review of developments made until now on this topic; it provides an overview of microwave scanning techniques for crack detection. This article summarizes the abilities of these methods to identify and evaluate cracks (including describing their different physical properties). These methods include applying filters based on dual-behavior resonators (DBRs), using complementary split-ring resonators (CSRRs) for the perturbation of electric fields, using waveguide probe-loaded CSRRs and using a substrate-integrated-waveguide (SIW) cavity for the detection of sub-millimeter surface and subsurface cracks.
Highlights
Failure or metal fatigue usually starts at the outside surface of a metallic object
The surface of the metal may be covered with paint or a similar compound, and the crack may still be detected because microwaves penetrate dielectric materials
3-mm-deep and 200-μm-wide cracks showed (i) a significant improvement in the sensitivity when using the first-order dual-behavior resonators (DBRs) arrangement, (ii) a connection between the spatial resolution and the width of the high-frequency stub of the DBR filter and (iii) the likelihood of sensing and imaging the crack for any dimension based on the DBR sensor
Summary
Failure or metal fatigue usually starts at the outside surface of a metallic object. Nuclear plants, aircraft fuselages, steel bridges and steam generators are examples of applications in which metal fatigue or failure is likely to occur. After 1993, near-field microwave crack detection techniques and approaches that use open-ended waveguide probes were introduced [9,10,11,12,13,14,15,16,17]. The surface of the metal may be covered with paint or a similar compound, and the crack may still be detected because microwaves penetrate dielectric materials. A broad depiction of near-field microwave methodologies and techniques using open-ended waveguide probes established in the early 1990s for evaluating and detecting cracks is addressed in [17]. These methodologies were extended and used for detecting V-shaped [18] and tilted [19] cracks. These methods include open-ended rectangular probes, open-ended coaxial probes, filters using dual-behavior resonators (DBRs), a substrate-integrated-waveguide (SIW) cavity and a complementary split-ring resonator (CSRR)
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