Research On The Experiments Of Non-Destructive Testing Based On Pulsed Eddy Currents Technology

Pulsed Eddy Currents (PEC) technology is a novel Non-Destructive Testing method developed in recent years. The rich frequency components in pulsed exciting are also included in the feedback response from the test sample. So comparing with the traditional eddy currents testing technology, PEC technology can reach a much deeper penetration and get information from various depth of the test sample in one measurement. By using appropriate signal processing method, PEC technology is able to measure the thickness or defects of the test sample precisely. PEC technology is being widely used in the measurements of ferromagnetic and non-ferromagnetic material nowadays.Based on the research and development in PEC technology of the world, theory and advantages of PEC technology are introduced. A kind of PEC experiment equipment design is discussed in detail. An exciting source based on Direct Digital Synthesis (DDS) and integrated power amplifier is designed. Comparing the differential probe with absolute probe, some effective factors e.g. temperature drift, diameter of enamel wire and turns of coil in probe size and resolution are presented. The signal-gating (trigger) circuit based on SCM (Single Chip Micyoco) and the signal processing circuit based on instrumental amplifier are designed. A series of experiments are taken on ferromagnetic pipes with different artificial defects and natural defects after the equipment is completed. The experiment results verify that the experiment equipment is able to detect wall loss of the ferromagnetic pipe in the area of the probe's footprint. The equipment is also able to detect the different thickness of Aluminum plates. But it can't detect the local defects of the ferromagnetic plate. So optimization of probe structure is needed to enhance the effect of magnetic focusing to improve the maximum lift-off distance of the probe. Also the theoretical modeling is needed to design a proper probe to detect the local defects of the ferromagnetic plate.The success of the experiment equipment is a promising step of PEC-based instrument design. PEC-based instrument have bright prospects with the increasing demands from the pipe building and testing projects in China.