Thermographic techniques for the detection of cracks in metallic components

Work on three thermographic NDE techniques that have been developed to locate and image cracks in metallic components is reviewed. These techniques are: thermosonics (sonic IR, ultrasonically stimulated thermography); laser spot thermographic imaging; and pulsed eddy current stimulated thermography. The three techniques are explained and examples are given of their performance in imaging well-characterised cracks. Factors concerning the practical and reliable implementation of the techniques are discussed.