I have been reading of some success that some people have had using thermography for crack detection. From what I could gather the best methods for crack detection in ferrous metals was eddy current or MFL. Are any of you aware of thermography being used instead of eddy current or MFL and what kind of success can one expect? I know thermography can be used for large cracks, but I did not know that it was sensitive enough to use on really small cracks like hair line fractures.
I think very often that it all depend on the inspection parameters. It doesn't matter which NDT method your are talking about, they all have their limitations. Personnally from my experience with Eddy Current, I don't think it is good to for crack detection in ferrous materials austenitic stainless steel exculded, simply because of the permeability variation throughout the material. Now MFL, is another story.
From what I know of thermography your result will be dependent on the size of the defect in relation to the size (thickness). The other factor you have to consider is the limitation of the equipment you have. Thermography may be good for thin materials, but like everything else, it also has its limits. This is why no one NDT method can ever replace all the others.