Research On Directional Coils Of Nondestructive Pulsed Eddy Current Testing

Because of the briefness and practicability of Pulsed eddy current (PEC) testingtechnique, it developed quickly in recent years. There are certain restrictions on the detectionof anisotropy metal materials using the traditional cylindrical coil，which detects the averageregional magnetic field signal values. However, the rectangular probe has obvious advantageon the conductivity detection of anisotropy metal materials and can eliminate the edge effectso it has high research value. The paper mainly researches on the theory of PEC rectangularprobe using FEM and experiments, the following aspects included:1) The directional properties of PEC rectangular probe. Using the electromagneticsimulation software COMSOL, we compared two different placements of rectangular probeand the sensitivity of the three-dimensional direction. The results show that directionalcharacteristic of rectangular probe relates with the placement and the testing detection. Thedetection sensitivity of different directions will change as the probe size changes;2) Size parameters optimization of PEC rectangular probe. Based on the directionalproperties of rectangular probe, we analyzed the best size parameters of the two placed waysof the probe. Keeping two parameters constant and changing one parameter, we optimized thebest size parameters of the rectangular probe according to sensitivity and linearity;3) PEC testing system design and probe optimization experiment. We designed PECtesting system of rectangular probe which contains signal generating module, power amplifiermodule, signal amplification module, data acquisition module and so on. The simulationresults were verified by the experiment. It demonstrated that the effectiveness of PECrectangular probe optimization method.4) Experiment of stress measurement using PEC rectangular probe. Based on the probeoptimization experiment results, the tensile experiments were carried out using the optimalprobe, testing results show that: there is a linear relationship between the pulsed eddy currenttesting signal and the material stress signal, we can evaluate the material stress state using theeddy current testing signal.