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Eddy Current Testing (ECT) plays a key role in detecting cracks and defects in conductors. The present study examines for the first time how the subregion method as an effective mathematical and computational technique can be admixed with Finite Element Method (FEM) to study multiple defects parameters for ECT issues. Separating a defect region from the entire domain in any computational technique will save both time and storage space. Examples of different types of defects are presented in this article. A tangible result of processing time reduction by 90% has been achieved which has led us to consider the subregion FEM method as an effective method in solving different Nondestructive Evaluation (NDE) problems. An agreement between our results and others using classical FEM has been achieved which could lead to using this technique in online and field testing problems. The presented subregion FEM algorithm was verified experimentally with good agreement by testing Aluminum (T6061-T6) samples with defects. A Tunneling Magnetoresistive (TMR) sensor was used to measure the component of the magnetic field from normal to the sample top surface. A major component of minimizing processing time was achieved, which could lead to using this technique in online and field testing problems. [ABSTRACT FROM AUTHOR]

This paper presents an eddy current (EC) probe with orthogonal excitation coils that can change the exciting current direction electrically and tunnel magnetoresistive (TMR) sensor for inspection of stacked CFRP. As CFRP is electrically anisotropic, eddy current excited along the fiber direction is stronger than in other directions. A high sensitivity TMR sensor located at the center of the two orthogonal coils measures the z component of induced magnetic field (Bz) which constitutes the probe signal. The output of the sensor is 0 if the induced currents are symmetric about the sensor. Signals of defects in different orientations depend on the direction of the exciting current. The operation of the probe is validated using a finite element model. A prototype was built and experimental results from CFRP sample with defects in different orientations are presented and analyzed. [ABSTRACT FROM AUTHOR]

Eddy current methods are commonly used in the inspection of riveted multilayer structures. In a practical scenario, steel rivets may be magnetized to varying levels which can distort the magnetic field and pose a major challenge since the distortion can result in false positives and negatives. This paper presents an invariance transformation procedure that renders the signal insensitive to changes in magnetization while retaining the sensitivity to defect information. The approach is first implemented on simulated data, where the signals from magnetized steel rivets can be generated under controlled variation of relative permeability. The algorithm is then validated on experimental data acquired using steel rivets with different residual magnetization levels. [ABSTRACT FROM AUTHOR]