EddyCentre advanced modelling

The EddyCentre Advanced Modelling is used to model the eddy-current probe signal when a volumetric defect has been introduced into the work-piece or ferrite has been placed in the probes windings; or both. The presence of this defect alters the flow of the eddy-currents in the work-piece, which changes the magnetic field induced by this current.

Ferrite changes the incident field generated by the windings and also interacts with the magnetic field created by the induced eddy-currents. These changes alter the magnetic field in the probe and cause a change in its impedance.

EddyCentre defect modelling

The EddyCentre defect model works by:

Modelling the defect volume using a number of equal rectangular cells or elements, each with a constant conductivity value. For cylindrical geometries, each element is actually a sector.
Modelling how an electrical source in each cell contributes to the field in all the remaining cells and stores the resulting matrix.
At each scan position, modelling the incident field in the centre of each of the cells.
At each scan position, solving the matrix equation, with the incident field as the forcing function, for the unknown scattered field in the defect volume. The sum of the dot product of incident and scattered field in each cell is then proportional to the impedance change for absolute probes or difference in potential for differential probes.

If a scattered field is being modelled an extra step is added to model the field in the desired region with the probe and the scattered field in each cell as contributing sources.

EddyCentre ferrite probe modelling

The EddyCentre ferrite probe model is a numerical model which solves the forward problem of predicting the ferrite-cored probe response to a volumetric defect in any multi-layered planar work-piece. The EddyCentre ferrite probe also models the incident and scattered electric and magnetic fields created by ferrite-cored probes in any region of the planar work-piece. The defect can be in any conducting region, but the region must be non-ferrous..

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