Eddy current method for detecting sub-surface defects in metallic substrates, e.g. for detecting corrosion defects in aircraft, based on inspection of components using Eddy current probes of different frequencies

摘要

Method in which Eddy currents of upper and lower frequencies are induced in a component under test. The current amplitude at the substrate surface is measured and the current field of the upper frequency Eddy current probe is subtracted from the field of the lower frequency probe, which enable a defect to be detected. Independent claims are made for a method for quantifying the volume of a sub-surface defect and a system for generating an outline of a sub-surface defect using Eddy current testing.