Effect of sensor shape on the equivalent impedance signature for the detection of defects using eddy current testing

Abstract

Eddy current testing is widely used for non-destructive evaluation of electrically conductive materials. This technique was recognized to be quite sensitive to defects affecting the geometry of a part or its electromagnetic properties, such as inclusions, cracks or corrosion. It is easy to implement, sturdy in the context of industrial applications and relatively inexpensive. Due to the growing need for reliability, the development of new eddy current systems is required. This work was dedicated to the design of new shapes of probes with the aim to increase detection capability. The objective is to assess how probe design can improve imperfection presence signature in a tested specimen. The methodology used is based on finite element simulation of B-scan process and calculation of the equivalent impedance seen across the terminals of the probe. Monitoring variations of this impedance for both the flawless control case and that with the presence of a defect was performed. Seven different shapes of probes were studied. It was found that the signature associated to the variation undergone by the impedance depends hugely on the probe geometry.