Abstract: The profiling eddy current detection technology is particularly suitable for rapid detection of the leading edge of blades with large curvature because of its good coupling and ability to effectively suppress the shaking in the detection process. The finite element model for the leading edge and the profiling coil is established for profiling eddy current detection of the leading edge of the turbine blade. The finite element method is used to analyze the detection signal characteristics of the blade leading edge with three typical defects (pit, long crack, and edge pit) with internal and external excitation, different inner diameter coils, and different frequencies. The simulation results show that the detection area can effectively cover the entire front edge area by implementing profiling eddy current detection on the front edge with large curvature. The higher the detection frequency, the higher the detection sensitivity. In the dual-coil detection mode, the externally excited internal receiver is more sensitive than the internally excited external receiver. When the size of the inner detecting coil is larger than the size of the defect, the smaller the inner diameter of the inner receiving coil, the higher its relative sensitivity. Based on the simulation results, a leading edge defect test block is made, and a leading edge profiling eddy current detection system is designed using the phase-locked amplification and graphical programming technology. The test results show that the profiling coil can effectively detect the typical leading edge defects. The amplitude and phase output results of the detected voltage are similar to the simulation results. The research findings can be used to guide detection of the leading edge of the blade with large curvature in engineering practice.

Key words: leading edge of blade, eddy current testing, finite element, profiling coil, defect, phase lock technology, LabVIEW