Detection and Sizing of Surface Cracks in Metals Using UHF Probe

Abstract

Crack formation on metal surfaces is a common industry problem that has catastrophic consequences if left undetected. While a variety of microwave and millimeter wave probes have been employed for crack detection, the utility of a ultra-high frequency (UHF) probe that operates at a much lower frequency when compared to other probes and provides enhanced resolution is explored in this paper. To benchmark the performance of the probe towards crack sizing, the response is compared qualitatively and quantitatively to a standard Ka-band open-ended rectangular waveguide and a V-band reflectometer. It is elucidated through line scans over a metal sample with cracks of various widths ranging from 0.25 mm to 1.75 mm. It is shown that the probe provides comparable indications of the cracks and has better signal to noise ratio (SNR) than the Ka-band waveguide. Furthermore, a magnitude image of the sample is also included to highlight the effectiveness of the probe towards providing a high-resolution image of the sample at a much lower frequency.