Experimental Research Based On Pulsed Eddy Current Testing Technology

As an important branch of eddy current testing which is one of the five major conventional non-destructive testing technologies, pulsed eddy current (PEC) non-destructive testing(NDT) becomes gradually a research focus in the field of non-destructive testing, due to its advantages, such as rich frequency, simple operation and low cost. However, now, the research is still in the development stage in our country, and the key technology is also in a few companies and research units. To understand the effect of PEC NDT on defects in the sample, and provides the theoretical foundation for its practical application. In this paper, by analyzing the experimental methods for pulsed eddy current sensor working parameters on the effect of pulsed eddy current detection sensitivity, and using the graphical representation to show the corresponding relationship between surface defect and the peak voltage surface defect detection signal. Specific research contents are as follows:(1) In this paper, I designed an experiment platform on the basis of studying the principle of pulsed eddy current detection. Including excitation signal source-, pulsed eddy current sensor signal acquisition and other laboratory equipment, and processed the aluminum plate into specimen with defects on it.(2) Analyzing the experiment of pulsed eddy current sensor working parameters just as:coil height、 lift-off height、 numbers of excitation t and detect turns、 excitation voltage、 excitation frequency、 duty ratio、 working environment temperature, and optimize the sensor capability combining with the experimental results and the actual situation.(3) Using the grid position measurement to characterizing the relationship between the specimen testing voltage peak and shape of the defect size, and find out the relationship between the depth and width of defect and the specimen testing voltage peak.The experimental results show these:(1) In theories, the coil and lift-off height gets lower, the numbers of excitation turns get less, the numbers of detect turns get more, the excitation voltage gets bigger, the excitation frequency gets lower, the better the performance of sensor will be. But, in the reality, the choose of pulsed eddy current sensor working parameters should connect with the practical situation.(2) There are some connections between the specimen testing voltage peak and shape of the defect size, and we can extract the rough shape of surface defect while eliminate the influence of lift-off effect.(3) When the width of defect unchanged, the deeper the defect the bigger the peak of specimen testing voltage, when the depth of defect unchanged, the wider the defect the bigger the peak of specimen testing voltage. And with the graphical representation of the connections between the specimen testing voltage peak and shape of the defect size, it can provide basis for the quantitative evaluation of defect.