Research Of Infrared Nondestructive Testing For The Common Defects Of Metal Pipes

Infrared nondestructive testing (IRT) is an abnormal detection means which combines the emission spectrum measurement and photoelectric conversion technique. This technology has an advantage of fast detection speed, safe, wide applicable range, straightforward results, etc. Now IRT have been widely used in the electronics industry, aviation, electrical, mechanical, the roof of humidity, air valve and pipe and other areas of testing work.At present there is a development trend from nondestructive testing to nondestructive evaluation. The production safety makes us no longer be satisfied with qualitative analysis, but requests for a quantitative analysis. Due to the large amount of transportation, continuous, high efficiency, low cost characteristics, pipeline transportation is becoming as one of the main mode of transportation. Pipe is easy to form Layered defects in casting and rolling process. As a result of the erosion of the internal corrosion medium and external stress corrosion environment, pipe is also easy to form wall thinning and surface crack in the using process. What’s more, pipeline is very long usually. So it’s of great importance to make an efficient nondestructive evaluation for the pipeline at regular intervals. This paper has made an infrared nondestructive testing for the Common defects of pipe from the aspects of simulation and experiment.Numerical modeling of pipes including delaminations and corrosion holes were constructed using ANSYS. For layered defects, the influence of pulse excitation parameters, depth of defects, thickness of defects, length of defects, thermal conductivity on maximum thermal contrast and time for maximum thermal contrast are analysised. Full width at half maximum was used to make an quantitative analysis of the lenth of layered defects. Basised on the front disscusion, this paper also discussed the effect law, which is arised from different depth and lenth, on the FWHM. As to the corrosion holes, a reflection and a transmission algorithms is used to calculate the depth of holes that’s of different diameters. The calculation results had achieved the expected goal. The results of the study show that a shallower, thickner, longger layered defect and higher thermal conductivity can bring about a bigger temperature difference; with a shallower, thinner, shortter layered defect and higher thermal conductivity, the time for maximum thermal contrast will be much more shortter.For the experiments, hot steam was used to heat tube containing through holes and surface cracks, and then temperature change was record by the thermgraphic system. Through the comparison of the thermograph in defferent time, the best time for the through holes’s detection is gotten. As to the surface crack, penetration treatment was carried out on the pipe which contains surface crack of different width before thermal excitation, the experimental result shows that this kind of method can greatly improve the crack detection sensitivity.