Eddy Current Microsensor Dedicated to the Nondestructive Testing of Conductive Plates

Abstract

To ensure the safety of transportation and prevent accidents, nondestructive testing by Eddy current (EC) is proposed to check the conditions of industrial parts. EC sensors are used for the inspection of defects in conductive parts using coil fed by alternative current. These sensors are sensitive to defects, easy to implement, and robust for industrial applications. In order to satisfy the requirement for both reliability and speed during inspection operations, innovative EC sensors that can provide higher sensitivity, better spatial resolution, and more information about the defect characteristics, such as microsensors, are developed. The miniaturization of these sensors’ coils conforms the sensor for micro-defects in critical parts and in complex materials. In this paper, a microsensor dedicated to EC application is studied and characterized to identify the coil parameters and to optimize the geometry of the probe. An approach for the modeling of microsensor dedicated to EC nondestructive applications is proposed. The moving band finite element method is implemented for this purpose to take into account the movement of the sensor and to simplify the modeling of EC testing configurations that use this kind ofsensor. Experimental validations were conducted on a nickel-based alloy specimen. The real and imaginary parts of the impedance at every position of the sensor computed by experiments and simulations were consistent with each other. Simulation results proved that the sensor was capable of detecting micro-defects with a size starting from 0.1 mm under the optimal excitation frequency of 0.8 MHz. It is not only sensitive to micro-cracks, but also it distinguishes the different crack sizes (length, width, anddepth).