Effects of Lift-Off on Microwave NDE Using an Open-Ended Rectangular Waveguide
Some authors have demonstrated recently the capability of microwave imaging of subsurface defects and material characteristics by scanning a suitably excited open-ended rectangular waveguide over a multi-layered composite [1,2]. This near-field approach of microwave NDE is in some aspects similar to the conventional eddy-current based techniques for defect detection and imaging in metals . Of course, in non-metallic materials, it is the discontinuities in the dielectric property, instead of the electrical conductivity, that gives rise to the defect signal. Bahr [4,5] has reported various techniques for the detection, discrimination, and processing of microwave signals, which are also applicable in the lower frequency regime typical of eddy current testing.
KeywordsDefect Detection Nondestructive Test Subsurface Defect Eddy Current Testing Lower Frequency Regime
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