Abstract
Koch curve exciting coil of an eddy current probe can adjust the eddy current distributing in more directions at a small domain to enhance the sensitivity of eddy current probe for short defect detection. In this study, a relative entropy and a cross entropy of tangential intersection angle spectrum are proposed to evaluate the eddy current distributions in the different directions when the eddy current probe is positioned at different lift-off distances and excited by different exciting frequency alternative currents. The eddy current distributions induced by a circular and a fractal Koch curve exciting coils are analyzed by the two entropy indices. With the increasing of the lift-off distance or the decreasing of the exciting frequency, the eddy current distributions induced by the Koch curve exciting coil are close to those induced by the circular exciting coil.
Highlights
Eddy current testing is a non-contact, rapid, and high efficient nondestructive testing method to evaluate the quality of the conductive materials and their parts.[1]
The primary magnetic field created by the exciting coils can be considered as a carrier wave, and the defect signal can be considered as a modulating signal
The three entropies are calculated by tangential intersection angle spectrum (TIAS) which is proposed by the literature,[19] so the TIAS is introduced as follows
Summary
Eddy current testing is a non-contact, rapid, and high efficient nondestructive testing method to evaluate the quality of the conductive materials and their parts.[1]. The principle of the EC testing is the fundamental knowledge for all aspects of the EC testing. In order to deeply recognize the mechanism of the EC testing, many models are created, such as equivalent circuit model, electromagnetic field model,[2] electromagnetic wave model, energy model,[3] EC disturbance model,[4] and so on. The principle of EC testing can be considered to be a communication model. An exciting coil and a pick-up element can be likened to a transmitting antenna and a receiving antenna, respectively. The primary magnetic field created by the exciting coils can be considered as a carrier wave, and the defect signal can be considered as a modulating signal. All of the models mentioned above can be unified to Maxwell’s equations
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