3D theoretical modelling for directional eddy current inspection with rectangular coils

Rectangular coils have caught increasingly attention in the field of eddy current inspection due to its directional capability to the material variation within the conductors, compared with circular coils. In this paper, the magnetic-field-based modelling has been realised to simulate magnetic field signals from solid-state magnetic field sensors. The analytical model, i.e. Extended Truncated Region Eigenfunction Expansion (ETREE) has been modified from 2D cylindrical coordinate system to 3D Cartesian coordinate system whilst the dimension of the sensor in the 3D model is still taken into account. Based on the analytical and Finite Element Modelling (FEM), rectangular sensor design and evaluation has been realised with the help of experimental study. Particularly, directional eddy current inspection using rectangular coils used for 3D defect characterisation and stress measurement has been studied.