Yunxing Shi

Approach for removing ghost-images in remote field eddy current testing of ferromagnetic pipes

In the non-destructive testing of ferromagnetic pipes based on remote field eddy currents, an array of sensing coils is often used to detect local defects. While testing, the image that is obtained by sensing coils exhibits a ghost-image, which originates from both the transmitter and sensing coils passing over the same defects in pipes. Ghost-images are caused by transmitters and lead to undesirable assessments of defects. In order to remove ghost-images, two pickup coils are coaxially set to each other in remote field. Due to the time delay between differential signals tested by the two pickup coils, a Wiener deconvolution filter is used to identify the artificial peaks that lead to ghost-images. Because the sensing coils and two pickup coils all receive the same signal from one transmitter, they all contain the same artificial peaks. By subtracting the artificial peak values obtained by the two pickup coils from the imaging data, the ghost-image caused by the transmitter is eliminated. Finally, a relatively highly accurate image of local defects is obtained by these sensing coils. With proposed method, there is no need to subtract the average value of the sensing coils, and it is sensitive to ringed defects.

Development of a continuous testing apparatus for temperature reduction performance of cool coatings.

The working principle of a continuous testing apparatus for the temperature reduction performance of cool coatings is presented in this work. The apparatus consists of infrared reflector type lamps, an adiabatic box, and a data acquisition system. It was calibrated with the different conventional reference panels. The tests for dynamic and steady state temperature reduction performances were illustrated with two cool coatings. Results obtained directly from the simultaneous measurement are in good agreement with those calculated from separate measurements, thus confirming this apparatus as a valuable experimental tool for research and development of cool coatings.