There has been a growing need in recent technology of gas turbines in combined cycle to assess the remaining life of high temperature components. It is also required that the nondestructive assessment be more accurate in maintaining combined cycle plants. This paper describes the use of a simulator solving forward and inverse problems under eddy current testing, in parametric studies of inspection parameters for 1100°C-class gas turbine blades in terms of test probe capabilities, frequencies and signal interpretation. The simulator is based on a differential formulation constructed with a magnetic vector potential and a 3-dimensional edge-based finite-element modeling method. Its features are forming coils and defects independent of a whole finite element model, very fast eddy current response predictions, and identifications of electromagnetic properties. Using the simulator, optimal sensor types and test frequencies are determined in terms of assessment of degradation, selectability between surface-breaking and subsurface cracks, reconstruction of crack profiles, and detection of multiple cracks.

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