| It is widely recognized that the detection of small and deep defect in metal materials such as corrosion,cracks and other complex defects still pose an important research subject to NDE community in a number of fields ranging from the aerospace,navigation to nuclear energy field.Nowadays the development of non-destructive testing technology has been quite mature,but the method for small and deep defect detection in the metal materials is very scarce.Originated from eddy current detection,the pulsed eddy current detection provides the possibility to detect small defects and deep defects in these materials,whose response signals contain richer defects information for the advantages of wide spectrum,fast scanning and no-contact inspecting.For these reasons,this paper highlights firstly the research background and the related research of pulsed eddy current testing technology both inland and overseas.In the following chapter,the principle of pulsed eddy current testing is introduced,the skin depth is analyzed and the typical signals are described.In chapter 3,the finite element theory and numerical simulation are applied for pulsed eddy current detection technology.The 2D finite element model is established to study the impact of the excitation signal parameters and the electromagnetic properties of materials on the detection of pulsed eddy current defects.In chapter 4,for studying the influence of different types of defects on the pulse signal,the three-dimensional modeling is built and calculated,and the results are analyzed.In chapter 5,based on the pulsed eddy current nondestructive testing system,the experiments are carried out to study the impact of the existing of defects on the signals of pulsed eddy current detection in different lengths,width and different shapes in aluminum-manganese alloy specimen.The extraction,effective processing of collected signals and three-dimensional imaging of pulsed eddy current defect detection are completed. |
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