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Microwave NDT: An Inspection Method

Until recently, ASNT classified microwave testing (MW) as a technique under electromagnetic testing (ET) (ASNT, 2004). In fact, the ET method comprised a number of techniques that have little in common, such as eddy current, microwave, and magnetic fluxleakage (ASNT, 2004). Furthermore, the term electromagnetic applies to a wide spectrum of NDT methods including radiography, infrared, laser, aforementioned techniques, and many others. The Microwave Testing Committee was established in 2014 and the method was included in the 2016 editions of ANSI/ASNT CP-105: ASNT Standard Topical Outlines for Qualification of Nondestructive Testing Personnel and ASNT Recommended Practice No. SNT-TC-1A: Personnel Qualification and Certification in Nondestructive Testing. This is justified since there are an increasing number of MW applications and techniques, more research, and more industrial applications than ever before. Within ASNT committee work, efforts are underway to develop MW certifications for Level I and Level II inspectors. The purpose of this paper is to provide a broad and introductory perspec-tive to MW and provide the technical justification as to why MW should be its own method in support of ASNT’s recognition of MW. There is not enough room in this paper to give justice to all of the formidable techniques, example applications, and noteworthy contributors since the 1950s, when MW began. Moreover, there is insufficient room to even simply list the references. For additional details, the reader is referred to these particularly comprehensive references that contain many additional references (Kharkovsky and Zoughi, 2007; Zoughi, 2000). Additionally, the bibliography at the end of this paper lists related citations for each subsection as evidence of the activity within MW. The goals of this paper are to introduce MW, describe materials charac-terization and imaging techniques with example applications, and a final discussion. Materials characterization describes trans-mission line, open-ended waveguide, and free-space techniques. Imaging describes near-field, lens-focused, synthetic-focused, and real-time techniques.


ASNT, “Introduction to Nondestructive Testing,” <>, American Society for Nondestructive Testing, Columbus, Ohio, accessed 20 February 2016.

ASNT, Nondestructive Testing Handbook, third edition: Vol. 5: Electromagnetic Testing, American Society for Nondestructive Testing, Columbus, Ohio, 2004.

Kharkovsky, S., and R. Zoughi, “Microwave and Millimeter Wave Nondestructive Testing and Evaluation – Overview and Recent Advances,” IEEE Instrumentation & Measurement Magazine, Vol. 10, No. 2, 2007.

Pozar, D.M., Microwave Engineering, third edition, John Wiley & Sons, Inc., Hoboken, New Jersey, 2005.

Zoughi, R., Microwave Non-Destructive Testing and Evaluation, Kluwer, Dordrecht, Nether-lands, 2000.

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