Effective probe response calculation using impedance boundary condition in eddy current NDE problems with massive conducting regions present

A 3-D finite element scheme is described for calculating probe responses in eddy current nondestructive evaluation (NDE) problems if massive conducting regions with small penetration depth are in the vicinity of the host specimen. These problems are related to the eddy current inspection of the tube support plate or tube sheet zones in PWR steam generator tubing. Recently, an efficient finite element scheme has been introduced to calculate the probe responses outside these zones. As a sequel to that work, the authors extend the technique for the tube support plate and the tube sheet zones. They use impedance boundary conditions (IBC) on the surface of the massive conductors and evaluate the probe responses due to these components by performing an integral over these IBC surfaces, thereby ensuring the same accuracy as in the previous work for the flaw signals. Benchmark problems-models of tube support plate zones with defects-have been measured and analyzed. The calculated probe responses show good agreement with the experimental data.