DETECTION OF MICRO‐CRACKS ON METAL SURFACES USING NEAR‐FIELD MICROWAVE RESONATORS

This paper demonstrates how micro‐cracks at the surface of metals can be detected and imaged by using near‐field microwave resonators. It deals with two novel sensors: a first‐order dual‐behavior resonator (DBR) band‐pass filter probe and a first‐order DBR filter with an opening in the ground plane. Measurements results carried out on a stainless steel mock‐up with several 200 μm wide EDM rectangular surface notches are presented showing the high sensitivity of the DBR probes and their ability to differentiate between notches of different depths.