Abstract: It is difficult to detect flaws in multi-layered structures of aircraft fuselage lap splices. Pulsed eddy current (PEC) is the effective method that has been demonstrated to be capable of quantifying this defect. Time frequency analysis techniques are used to quantify cracks appearing in aircraft structure. With the purpose of overcoming the problem of low accuracy of PEC in the cracks classification, a new feature, termed as frequency spectrum separating point, is proposed to enhance the accuracy in classification of defects. The agreement between theory and experiment shows that the present method is correct.

Key words: Crack, Aircraft structure, Defect classification, Quantification, Scanned pulsed eddy current, asymmetric pump, excavator arm, single rod cylinder, pump controlled cylinder