Mesh and Boundary Considerations in the Numerical Modeling of Large 3-D Electromagnetic NDT Geometries

Numerical modeling is particularly useful for simulating the energy/defect interactions associated with electromagnetic methods of nondestructive testing, because of the relative ease with which the awkward boundary conditions and shapes can be handled. With the increasing availablity of commercial code it is worthwhile reminding the potential NDT user of the old computer adage “garbage in, garbage out”, as many modeling situations, particularly those associated with large pipeline structures, can present formidable discretization problems in 3D to even the most sophisticated of today’s computers, and one must take care in the choice of mesh used for any given problem. This paper describes some situations where mesh choice plays a significant role in the accuracy of numerical code predictions. Two examples considered here, for illustrating these difficulties are (i) the remote field eddy current method and (ii) the flux leakage method, for inspecting ferromagnetic pipelines.