Research On Electromagnetic Excitation Parameters For Active Electromagnetic-thermal NDT

In the method of active electromagnetic-thermal NDT, the exciting effect ofmaterial affects the accuracy of results directly. However， the selection ofelectromagnetic excitation parameter is one of the important factors that determineNDT effect. At present, the relevant researches mainly focus on the influence onsingle excitation parameters and single exciting effect indexes, however, impact onother parameters and the comprehensive relationship between multiple parameters andmultiple exciting effect indexes remains further research.In this paper, parameters that influence the exciting effect are taken as the object.Two kinds of electromagnetic exciting mode (namely transverse flux electromagneticexcitation and longitudinal flux electromagnetic excitation) are considered in thispaper. Parameters that influence the exciting effect are studied using the method oftheory, simulation and experiment.In the part of transverse flux electromagnetic excitation, parameters are studiedby theory and theoretical formula firstly, then the relation between electromagneticexcitation parameters (power consumption, coil length, coil equivalent diameter,lift-off distance, exciting period, etc) and excitation thermal effect was analyzedthrough orthogonal test. The mathematical model between parameters and excitationthermal effect was built based on the partial least-squares regression. The modelingerror of nine experiment samples is9.24%. Lastly, the model was verified by fifteenexperiment samples. The result shows that the average error of mathematical model is9.78%; exciting period affects most among the exciting parameters, followed bylift-off distance, coil equivalent diameter, coil length and power consumption.In the part of longitudinal flux electromagnetic excitation, parameters are studiedby theory and theoretical formula, then ANSYS finite element software are used to thesimulation analysis of parameters, and then the parameters are studied by experiment.Firstly, orthogonal experiments are used to analyze the relationship between excitingparameters (namely coil turns, coil lift-off, exciting period, exciting current and power consumption) and exciting effect indexes (namely surface temperature difference andheating rate).Secondly, the model of lognitudinal flux electromagnetic excitationbetween multiple parameters and multiple exciting effect indexes is established basedon partial least squares regression. For the nine orthogonal experiments, the modelingerrors of two exciting effect indexes samples are6.29%and5.03%. Finally,verification experiments are used to verify the established model, and the averageerrors of two exciting effect indexes are6.99%and5.80%respectively, the influenceof coil turns and exciting period on two exciting effect indexes is largest.