Diffusion-wave laser radiometric diagnostic quality-control technologies for materials NDE/NDT

The development of diffusion-wave diagnostic methodologies and their implem entation as laser infrared photothermal radiometric diagnostics for industr ial materials NDT, has resulted in two emerging NDE/NDT technologies. The s olution of the ill-posed thermal-wave inverse problem has achieved reconstr uctions of thermal-diffusivity depth profiles in engineering materials such as heat-treated steels and thermal-barrier coatings. A novel approach for surface roughness elimination was introduced, modeling roughness as white ( Gaussian) noise in the spatial coordinate. Furthermore, a novel semiconduct or radiometric NDE metrology capable of measuring the primary photoinjected free carrier parameters (recombination lifetime, electronic and thermal-di ffusivities, and surface recombination velocities) is also being developed. These emerging diffusion-wave technologies are described, and examples/cas e studies involving manufactured and thermally processed steels, thermal-ba rrier coatings and industrial Si wafers are discussed. (C) 2001 Elsevier Sc ience Ltd. All rights reserved.