Practical Implementation of the Impedance Method of Non-Destructive Testing

摘要

Use of the impedance method of nondestructive inspection on carbon fiber reinforced plastic (CFRP) skinned honeycomb structures and on solid aluminum panels was studied. The relationship between the measured impedance and defect size and depth was investigated. It is shown that the sensitivity of the method decreases rapidly with defect depth. For example, a 10mm diameter defect is reliably detected under an 0.5mm thick CFRP skin, but not under a 1mm thick skin. Reliability of the technique is greatly reduced on flexible structures. C-scan maps of the structures were produced using an impedance head and the vibrating rod transducer used in commercial testing instruments. The impedance head works satisfactorily and has the advantage over the vibrating rod transducer in that a direct measure of structural impedance is obtained.