Flash duration and timing effects in thermographic NDT

摘要

In conventional flash thermography a brief pulse of light with a full width half maximum duration of 2-4 ms is applied to the surface of a solid sample and the surface temperature response is recorded with an infrared camera. In practice, the flash duration is typically fixed, and the amplitude is the only adjustable flash parameter. Flash amplitude is normally adjusted to provide maximum illumination of the sample surface without causing saturation of the camera detector array. However, more precise interrogation of the subsurface structure is obtained if the timing parameters of the flash excitation and the detector are carefully determined and controlled. In particular, limiting the pulse duration and the offset between the pulse and the detector integration time significantly increases correlation between modeled and experimental results during the early post-flash frames. Additionally, a new method is described to precisely detect the initiation and duration of the pulse for common high performance infrared cameras.