Development And Test Of The Ac Field Detection Instruments

The Alternating Current Field Measurement (ACFM) technology is a new type ofelectromagnetic nondestructive testing technique rised in recent years,the method isnot subject to the lift-off effect, material properties,the influence of edge effectthe,canestablish a precise mathematical model,can be achieved quantitative measurements ofthe structure of the surface crack length and depth.In this paper, first described in detail the research status and development trendsof the alternating current field measurement technology,With alternating current fielddefect detection theory and ACFM works,establish a finite element model of the ACelectromagnetic field of defect detection,modeling and finite element analysis usingANSYS software on the alternating current field measurement technique.According tothe alternating current field measurement probe (the incentive probe,receiving probe)design theory,and experimental validation of the combination,to explore the optimalcombination of probes for this topic,and gives them specific parameters.Designedaccording to the characteristics of the detected signal alternating current fieldmeasurement technique,based on the principle of cross-correlation of the orthogonalvector-lock amplifier circuit,the successful realization of the separation of the usefulsignal and interference signals,which greatly facilitates the subsequent acquisition andanalysis.Also designed based on DDS technology quadrature signal source,and afterthe final selection of the appropriate DDS chip analysis,not only to achieve theexcitation signal in the excitation coil,two orthogonal vector-locked amplifier circuitis cross-reference signal,and all the way to a square wave signal behind the signalprocessing module to maximize use of resources,with a high cost.Designed aLabview-based defects in the visual detection software,hardware circuit design withthe front of the final constitute a complete ACFM detection system to complete theassembly of the apparatus,and in the case of consideration of electromagneticcompatibility.Instruments Finally,through the processing of the specimen tested andthe data were analyzed.