In the IR thermography non-destructive testing, image blurring introduced by noises and heat diffusion in the sample is an important problem. In this paper, a serial of image processing methods are proposed to eliminate the influence caused by noises and heat diffusion. By use of these methods, image averaging, median-value, binarization and gradient alternation have been done. The processed images' characteristics are clear, and the error of detection is smaller than 5 percent. It is showed that the technique can effectively remove the blurring in images, improve image resolution and give us distinct images that meet the need of IR thermography non-destructive testing technology.
The principles and methods are introduced to quantitatively detect the subsurface defect depth and size by pulse-heating IR thermography. The subsurface defects in different metal and insulating materials were quantitatively measured by using our home-made pulse-heating IR thermography non- destructive testing system. From our experimental results, it is shown that accurate information can be obtained during a shortly time after the surface of a target is heated by a thermal pulse. Especially for metals a fast recording of the images is required.
The theoretical and experimental studies of pulse-heating infrared thermography non-destructive testing technique are presented in this paper. Our home-made pulse-heating infrared thermography non-destructive testing system is introduced. The system mainly consists of an infrared thermal imager and pulse-heating sources. The infrared thermal imager can acquire images continuously at the speed of 25 frames per second. The imaging and analyzing processes are controlled by a computer. The special software was designed for this system. In order to get a high inspection resolution, the heating source must be an adequately fast pulse. In our system, two flash-tubes are used as pulse- heating sources to launch thermal waves on the target. About 7kj energy is discharged through two xenon tubes each time. Steel, aluminum and plastics testing samples are inspected by using this system. The inspection results are given. The advantages of this technique are no physical contact, large area, fast and quantitative non-destructive testing.
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