COMSOL Multiphysics Modeling for Design Optimization of Eddy Current Crack Detectors

E. Weststrate, M. Steinback, N. Rensing, and T. Tiernan
Radiation Monitoring Devices Inc., Watertown, MA, USA

Passing alternating current through a wire placed just above a conducting surface induces eddy currents in that surface. Any cracks present in the conductor modify the eddy current distribution, creating a magnetic field signature unique to the crack. This magnetic signature can be detected by placing magnetic field sensors such as magnetoresistive sensors or inductive loop pickups in close proximity to the cracks. Design optimization for the wire/sensor probe must also take into account the heat generated in the wire, and the geometry of the probe must allow both the wire and the sensor to be as close to the surface and the crack as possible. For use with curved surfaces the multi-turn conducting coil may be tapered, with many of the turns both further from the surface and further from the probe, thus providing diminishing benefit. We have developed COMSOL models to optimize the design of eddy current probes for crack detection for a variety of test object geometries.