Defect identification and evaluation based on three-dimensional magnetic field measurement of pulsed eddy current

摘要

The Pulsed Eddy Current (PEC) testing technique is an effective method of quantifying defects in multi-layer structures. To detect defects in airframe structure, a novel PEC testing probe consisting of a rectangular sensor and three pick-up coils was proposed. In different directions of sensor scanning, the three-dimensional magnetic field of a rectangular sensor was researched. Based on establishing the detecting system, defects can be identified effectively by setting a safety zone on the butterfly-shaped graph in different directions of sensor scanning, which can eliminate the velocity effect of the probe. The depth of defect can be evaluated quantitatively by extracting peak amplitude and zero-crossing time. The length of defect can be evaluated quantitatively by utilising By and Bz waves, which can improve measurement precision and detection dependability. The PEC testing is helpful for imaging inspection of defects in ageing aircraft structure.