Defect identification method for capacitive-inductive dual-mode sensors with lift-off interference

Abstract

The capacitive-inductive dual-mode probe provides a defect detection solution that allows simultaneous or sequential eddy current detection and capacitive imaging detection, known as capacitive-inductive dual-mode detection. The dual-mode detection combines the advantages of the two detection techniques and can be used to detect multiple types of defects in “insulator-conductor” multilayer hybrid structures. However, its high sensitivity poses a challenge as the probe's responses a susceptible to interference from lift-off variations, leading to non-relevant indications in the results that is not indicative of defects or anomalies. In this study, the Lift-off Characteristics (LoC) of the hybrid structures are studied, and an effective method for identifying relevant indications such as defect and anomaly for dual-mode sensor response signals with lift-off interference by combining the testing data of both detection modes and the LoC curve is proposed. A series of validation experiments were conducted to demonstrate the effectiveness of the proposed method in defect identification and classification. The results confirmed that the method effectively identified defect from lift-off interference and significantly reduced the occurrence of false judgments, thereby enhancing the reliability of the dual mode detection. Furthermore, the feasibility of utilizing the method to identify relevant indication when the sensor is tilted was also demonstrated.