On Boundary Integral Equation Method for Field Distribution under Cracked Metal Surface
Two approaches to the problem of the AC magnetic field distribution inside conducting media are currently used. One consists of solving the quasi-stationary Maxwell differential equations subject to certain boundary conditions. Another one is based upon certain boundary integral equations that involve only the field components at the boundary surface [1,2]. Aside from some numerical advantage in treating unknowns of a lower dimension, the second method fits better the common formulation of the eddy current NDE, which aims at determination of the total impedance of a metal part (or its change due to a defect). The impedance is related to the integrated energy flux through the metal surface and as such it can be expressed in terms of the field components at the surface exclusively.