It is always a difficult problem for the non-destructive testing of tubular specimen with multi-layer composite structure. Light pulsed thermography was applied on this kind of specimen, but only near surface defects can be detected because of low stimulation power and thermal diffusion. In this paper, a new thermography method for tubular specimen testing is proposed, which the hot and cold water is applied to circulate inside the tubular specimen as a periodic heat stimulation, infrared reflector is also designed to inspect 360 degree of tubular specimen at one thermography. Typical composite tubular specimen with embedded defects are detected by this method and device. The results of the thermal images show that it is an effective method for the testing of composite tubular specimen. Furthermore, data processing is discussed because of the periodic stimulation, time-frequency transformation can be applied to the thermal image sequence to get the phase image and improve the detection signal-to-noise ratio.
The infrared radiation intensity of object is directly determined by emissivity, we design a new method regarding to self-regulated infrared radiation applied to different background by using electroluminescent material. The application of electroluminescent material to the target surface can further realize the variable even autonomous regulation of the infrared characteristics of the target. By controlling the emissivity of the material, the radiation intensity of the target is as close to the background as possible, therefore the discrimination of the target and the background are reduced. The target radiation intensity can be changed dynamically with the environment, especially the process is reversible, and thus this application becomes an effective control method of the optical parameters of the target characteristics.