Simulation and Implementation of a High Sensitive Differential Eddy Current Giant Magnetoresistance Probe for Non-Destructive Testing

This paper presents the design and implementation of a high-sensitivity eddy current (EC) sensor based on giant magnetoresistance (GMR) to assess cracks in conductive materials. This approach's originality uses two symmetrical giant magnetoresistance sensors in a differential configuration using commercial GMR elements inserted on a coil in a ferrite pot. The background signal measured by the sensor is infinitesimal if there is no crack in the sample. Therefore, the designed sensor demonstrates a high sensitivity to the presence of cracks where the GMRs mounted in differential allow to reduce the background voltage's impact. On the other hand, The GMR-based EC probe with a ferrite pot core is more sensitive to the presence of cracks than the conventional EC sensor without a ferrite pot core. This work introduces the notion of the GMR sensor's effective area (EA) after being calculated and optimized using the inverse problem (particle swarm optimization method). The operation of the differential GMR sensor is validated using a 3D finite element model based on the (A, V-A) formulation and experimental measurements. The prototype of the differential GMR sensor is developed and tested. Experimental results are obtained to evaluate cracks machined on an aluminum standard.