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

The development of diffusion-wave diagnostic methodologies and their implementation as laser infrared photothermal radiometric diagnostics for industrial materials NDT, has resulted in two emerging NDE/NDT technologies. The solution of the ill-posed thermal-wave inverse problem has achieved reconstructions 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 semiconductor radiometric NDE metrology capable of measuring the primary photoinjected free carrier parameters (recombination lifetime, electronic and thermal-diffusivities, and surface recombination velocities) is also being developed. These emerging diffusion-wave technologies are described, and examples/case studies involving manufactured and thermally processed steels, thermal-barrier coatings and industrial Si wafers are discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.