We call them inner cracks which are open under coil, and outer cracks exist at the opposite side. I summarizes the important dimensions, material properties, and test conditions. By symmetry, a half-model of the problem was constructed using the finite elements shown in Fig. 5. Table II summarizes the discrete data and the information about the ICCG method. The admissible parameters are taken as 0.1 mm 1.15 mm.
Excellent agreement demonstrates the effectiveness of numerical modeling for the forward problem.
Giving the length, opening, location, and breaking side of each crack is mere assumption for simplification of the modeling. However the location is presumed from the distribution on the impedance map in Fig. 7, and the side is predicted in the phases of the signals. Output least square errors are shown in Fig. 8 until convergent parameters are obtained from initial conditions. It can be seen that they decrease at every iteration in each case.