Research On Thickness Dynamic Testing Technology And System Of Multi-layered Plates Using Eddy Current Method

Thickness is one of the key factors of the plate quality. The thickness measurement of plate becomes more and more important, especially the thickness measurement of multi-layered plate, so researching an effective method to control the thickness of plate is very important.Supported by a National Natural Science Foundation and a multi-layered plate's thickness testing system project of a company, this paper researched the multi-layered plate's thickness testing method and on-line testing system based on the Eddy Current Testing (ECT) method and Multi-frequency ECT technology. The detailed content and chapter arrangement of this paper are as follows:Chapter one: The practice and research meaning of multi-layered thickness testing is expatiated, and current research situation of ECT technology is summarized. At last, combining with the researching projects, the main content and frame of this paper is presented.Chapter two: The basic theories of ECT are introduced; deep thickness ECT technology and Multi-frequency ECT technology are researched. The effective magnetism conductibility and characteristic frequency of the placed eddy-current probe coil is also researched, and a method of their calculation and selection is presentedChapter three: The theory and application of Giant Magnetoresistance (GMR) effect is introduced. Combining with deep ECT technology, a new ECT method is presented and the multi-layered plates ECT set based GMR sensors are designed.Chapter four: A four-layered thickness ECT model based on ECT method is constructed by introducing the magnetism vector, the probe coil impedance mathematical model is investigated, and this model is validated by experiment.Chapter five: System's scheme based on the requirement of the multi-layered plate's thickness testing system is presented. Virtual Instrument (VI) and PC flat are selected, and the main frame of this system is designed.Chapter six: Graphic programming language LabVIEW and COM components mixed programming technology are used, the multi-layered thickness testing prototype system is developed based on VI flat.In the end, all of the work in this dissertation is summed up, and the future researches on multi-layered ECT technology are prospected.