Impact of crack geometry on transmission frequency characteristics in eddy-current non-destructive evaluation

Swept frequency eddy-current non-destructive evaluation of defects is investigated in this paper. Influence of crack geometry on transmission frequency characteristics is experimentally studied. Plate specimens having electro-discharge machined (EDM) slits of various lengths and depths are inspected using an eddy-current probe. The probe is fixed at certain positions during the inspection. Frequency of the exciting signal is changed in a defined range and frequency transfer functions are studied. The presented results clearly show that the frequency transfer functions depend on the slit's dimensions. These unique results bring new insight into possible employment of fixed eddy current sensors driven with swept frequency signal for crack's evaluation.