The thermographic images of laser-heated spots or lines are perturbed by nearby cracks, providing NDE techniques for crack detection. Scanning with a laser line, rather than a laser spot, results in a substantial reduction in inspection time. 3D finite difference modelling results are presented that show the sensitivity of the laser-line thermography technique to cracks of varying lengths, depths and openings. A novel crack imaging technique is presented that is based on assembling the second spatial derivative thermal images of a scanned laser line. Experimental results show the new technique to image cracks with openings as small as a few micrometres. The scanning time of the laser-line thermography technique is shown to be over an order of magnitude smaller than that of the laser-spot thermography technique whilst producing crack images of similar quality.
- nondestructive evaluation
Li, T., Almond, D. P., & Rees, D. A. S. (2011). Crack imaging by scanning laser-line thermography and laser-spot thermography. Measurement Science and Technology, 22(3), . https://doi.org/10.1088/0957-0233/22/3/035701