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Millimeter Wave Detection of Surface-Breaking Cracks in Steel and Aluminum under Severe Corrosion and Paint

Many components of critical and heavily utilized infrastructure, such as ships, planes, bridges, and so on, are operating at or beyond their designed lifetime. Replacement is no longer an option, and “retirement for cause” is the current approach to maintenance and replacement. Consequently, there is an ever-increasing demand for efficient and robust nondestructive testing (NDT) methods and techniques that can determine the physical health of these structures. Large structures, which are primarily made of metals, either steel or aluminum, are susceptible to in-service corrosion and stress-induced cracking. Stress-induced cracks, particularly in heavily corroded steel members used in bridges, railroads, storage tanks, and similar structures, are difficult to detect using many of the standard NDT methods, increasing the risk of not being able to detect an existing crack. Microwave signals readily penetrate through dielectric materials such as paint and corrosion byproducts (such as rust) and can interact with the underlying metal, rendering cracks detectable. In this paper, the implementation of a microwave imaging system that utilizes the synthetic aperture radar (SAR) approach to detect surface-breaking cracks (in the form of manufactured narrow notches) in steel and aluminum samples under heavy corrosion and corrosion-preventive paints is investigated. In addition, the influence of signal polarization direction relative to crack direction and the cyclical severity of corrosion inducement are investigated. The resulting SAR images are analyzed and compared to numerical simulations to identify the real-world capabilities and theoretical limitations of the technique.


Davis, J.R. ed., 1999, Corrosion of Aluminum and Aluminum Alloys, ASM International, Materials Park, OH.

Bao, Y., M.T. Ghasr, K. Ying, G. Chen and R. Zoughi, 2017, “Microwave Synthetic Aperture Radar Imaging for Nondestructive Evaluation of Mechanically Stabilized Earth Walls,” Materials Evaluation, Vol. 75, No. 2, pp. 177–184.

Bushberg, Jerrold T., J. Anthony Seibert, Edwin M. Leidholdt, Jr., and John M. Boone, 2011, The Essential Physics of Medical Imaging, third edition, Lippincott Williams & Wilkins, Baltimore, MD.

Case, J.T., and S. Kenderian, 2017, “Microwave NDT: An Inspection Method,” Materials Evaluation, Vol. 75, No. 3, pp. 338–346.

Case, J.T., M.T. Ghasr, and R. Zoughi, 2011, “Optimum 2D Uniform Spatial Sampling for Microwave SAR-Based NDE Imaging Systems,” IEEE Transactions on Instrumentation and Measurement, Vol. 60, No. 12, pp. 3806–3815.

Fallahpour, M., J.T. Case, M.T. Ghasr, and R. Zoughi, 2014, “Piecewise and Wiener Filter-Based SAR Techniques for Monostatic Microwave Imaging of Layered Structures,” IEEE Transactions on Antennas and Propagation, Vol. 62, No. 1, pp. 282–294.

Gallion, J., 2019, “Microwave Detection of Surface Breaking Cracks in Metallic Structures under Heavy Corrosion and Paint,” M.S. Thesis, Electrical and Computer Engineering Department, Missouri University of Science and Technology (S&T),

Gallion, J., and R. Zoughi, 2017, “Millimeter Wave Imaging of Surface-Breaking Cracks in Steel with Severe Surface Corrosion,” IEEE Transactions on Instrumentation and Measurement, Vol. 66, No. 10, pp. 2789–2791.

Ghasr, M.T., M.A. Abou-Khousa, S. Kharkovsky, R. Zoughi, and D. Pommerenke, 2012, “Portable Real-Time Microwave Camera at 24 GHz,” IEEE Transactions on Antennas and Propagation, Vol. 60, No. 2, pp. 1114–1125.

Ghasr, M.T., M.J. Horst, M.R. Dvorsky, and R. Zoughi, 2017, “Wideband Microwave Camera for Real-Time 3D Imaging,” IEEE Transactions on Antennas and Propagation, Vol. 65, No. 1, pp. 258–268.

Herzberg, Eric, 2012, “DoD Estimates the Annual Cost of Corrosion for Navy Ships: Latest Report Employs Data from Fiscal Years 2008–2010,” CorrDefense, accessed at on 31 July 2019.

Huber, C., H. Abiri, S. Ganchev, and R. Zoughi, 1997, “Modeling of Surface Hairline Crack Detection in Metals Under Coatings Using Open-Ended Rectangular Waveguides,” IEEE Transactions on Microwave Theory and Techniques, Vol. 45, No. 11, pp. 2049–2057.

Hughes, D., N. Wang, T. Case, K. Donnell, R. Zoughi, R. Austin, and M. Novack, 2001, “Microwave Nondestructive Detection of Corrosion Under Thin Paint and Primer in Aluminum Panels,” Subsurface Sensing Technologies and Applications, Vol. 2, No. 4, pp. 435–451.

Kharkovsky, S., and R. Zoughi, 2007, “Microwave and Millimeter Wave Nondestructive Testing and Evaluation – Overview and Recent Advances,” IEEE Instrumentation & Measurement Magazine, Vol. 10, No. 2, pp. 26–38.

Kharkovsky, S., M.T. Ghasr, and R. Zoughi, 2009, “Near-field Millimeter Wave Imaging of Exposed and Covered Fatigue Cracks,” IEEE Transactions on Instrumentation and Measurement, Vol. 58, No. 7, pp. 2367–2370.

Laviada, J., M.T. Ghasr, M.L. Portugués, F. Las-Heras, and R. Zoughi, 2018, “Real-Time Multi-View SAR Imaging Using a Portable Microwave Camera with Arbitrary Movement,” IEEE Transactions on Antennas and Propagation, Vol. 66, No. 12, pp. 7305–7314.

McClanahan, A., S. Kharkovsky, A. Maxon, R. Zoughi, and D.D. Palmer, 2010, “Depth Evaluation of Shallow Surface Cracks in Metals Using Rectangular Waveguides at Millimeter-Wave Frequencies,” IEEE Transactions on Instrumentation and Measurement, Vol. 59, No. 6, pp. 1693–1704.

NACE, 2002, “Corrosion Costs and Preventative Strategies in the United States,”, August 2018.

Qaddoumi, Nasser, and Reza Zoughi, 1996, “Microwave Detection of Corrosion Under Paint and Composite Laminate Coatings,” Proceedings SPIE Volume 2945, Nondestructive Evaluation of Aging Aircraft, Airports, and Aerospace Hardware, 14 November 1996, Scottsdale, AZ, doi: 10.1117/12.259109.

Qaddoumi, N., E. Ranu, J.D. McColskey, R. Mirshahi, and R. Zoughi, 2000a, “Microwave Detection of Stress Induced Fatigue Cracks in Steel and Potential for Crack Opening Determination,” Research in Nondestructive Evaluation, Vol. 12, No. 2, pp. 87–103.

Qaddoumi, N., L. Handjojo, T. Bigelow, J. Easter, A. Bray, and R. Zoughi, 2000b, “Microwave Corrosion Detection Using Open Ended Rectangular Waveguide Sensors,” Materials Evaluation, Vol. 58, No. 2, pp. 178–184.

Rajab, K.Z., M. Naftaly, E.H. Linfield, J.C. Nino, D. Arenas, D. Tanner, R. Mittra, and M. Lanagan, 2008. “Broadband Dielectric Characterization of Aluminum Oxide (Al2O3),” Journal of Microelectronics and Electronic Packaging, Vol. 5, No. 1, pp. 2–7.

RF Cafe, 2019, “Dielectric Constant, Strength, & Loss Tangent,” RF Cafe: Tech News, Resources, & Entertainment, accessed at on 31 July 2019.

Yeh, C., and R. Zoughi, 1994, “A Novel Microwave Method for Detection of Long Surface Cracks in Metals,” IEEE Transactions on Instrumentation and Measurement, Vol. 43, No. 5, pp. 719–725.

Zoughi, R., 2018, “Microwave and Millimeter Wave Nondestructive Testing Principles,” Materials Evaluation, Vol. 76, No. 8, pp. 1063–1069.

Zoughi, R., and S. Kharkovsky, 2008, “Microwave and Millimetre Wave Sensors for Crack Detection,” Fatigue & Fracture of Engineering Materials & Structures, Vol. 31, No. 8, pp. 695–713.

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