叶片前缘仿形涡流检测仿真与试验设计

仿形涡流检测技术因其耦合性好可有效抑制检测过程晃动而特别适合对大曲率叶片前缘快速检测。针对涡轮叶片前缘仿形涡流检测建立前缘及仿形线圈有限元模型，运用有限元方法分析叶片前缘凹坑、长裂纹、边沿凹坑3种典型缺陷在内外两种激励、不同内径线圈、不同频率等模式下的检测信号特征。仿真结果表明：大曲率前缘实施仿形涡流检测，检测区域可有效覆盖整个前缘区域，检测频率越高，检测灵敏度越高。双线圈检测模式下，外激励内接收比内激励外接收灵敏高，当内检测线圈尺寸大于缺陷的尺度时，内接收线圈内径越小，其相对灵敏度越高。结合仿真结论，制作前缘缺陷试块，采用锁相放大及图形化编程技术，设计前缘仿形涡流检测系统，试验结果表明，仿形线圈可有效检出前缘典型缺陷，检测幅值相位输出结果与仿真结论相似。研究成果可用于指导大曲率叶片前缘的工程实践检测。

Simulation and experimental design of profiling eddy current detection of blade leading edge

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.