engleski

An application of a coil impedance model in eddy-current nondestructive testing

The usage of eddy-currents is a well-established technique of nondestructive testing, which takes important place in applications such as testing of multi-layer structures in the aircraft industry, pipes in the oil industry and heat exchangers. The method is based on monitoring changes of the impedance of a coil due to changes of eddy-current flow within a material. The impedance is usually shown in an impedance plane. It is possible to infer potential defects in the object by automated processing of patterns in the plane or, more often, from interpretation of an experienced operator. The method can be improved with inverse procedures based on analytical models of the coil impedance.In this paper, we present a model-based, single-coil method for simultaneous measurement of inner diameter and electromagnetic properties of seamless, metallic tubes from impedance of a single coil measured at a single frequency. The single-coil method is based on an impedance model of an axially centralized coil inside a tube made of conductive, permeable material. We describe the model, optimization procedure and provide experimental results that confirm applicability of the proposed approach for measurement of the tube properties.

eddy-current method; coil impedance; model; inverse procedure; tubes; inner diameter; electromagnetic properties

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