Study on Optimum Frequency for Eddy Current Testing of Tubes by Numerical Modeling and Experimental Verification

The characteristic frequency and experimental methods are widely used at present for selection of exciting frequencies with which eddy current NDT of tubes are conducted. The methods are not accurate enough for finding the optimum frequency. The frequencies selected by the methods are always a little far from the optimum. A new method based on numerical modeling of flaw signals with ANSYS was developed. In this way the optimum exciting frequency was found. The optimum means that both the signals from ID and OD artificial defects were higher and the difference between the phases of the two signals reached nearly the maximum. The experiments of eddy current NDT on tubes with the ID and OD artificial defects were conducted. The results of the experiments agreeed with those of numerical modeling very well. It was concluded that the new method was accurate enough for finding the optimum exciting frequency.