Abstract: Traditional alternating current field measurement (ACFM) technique has advantages of quantitative defect detection and noncontact, but poor detective performances on deep-layer defects. Pulsed eddy current testing (PECT) has a better detectability in deep-layer defect, but poorer quantitative performances than ACFM, and moreover, it is easily interfered by lift-off due to using transient response signal analysis method so it is difficult to be applied practically. A method of alternating current filed measurement with pulsed signal excitation is proposed, which implements defect detection and quantitative evaluation by approach of transient signal analysis combined with 3D magnetic filed measurement based on pulsed response signal. Characteristics in the transient response signal which can reflect the variation law of magnetic field are extracted. Through the study it is found that the pulsed alternating current field measurement has not only the same detectability of surface defects as ACFM, but also an excellent capability of deep defect identification and quantitative evaluation.

Key words: Deep flaw quantitative evaluation, Defect identification, Pulsed ACFM, Solid butterfly-shaped graph