Résultats exploitables
A technique has been developed for the rapid inspection of engineering ceramic, metallic and organic coatings. The technique uses the beam from a small laser to create a surface thermal transient, which is recorded with a single infrared detection. The laser beam and the field of view of the detector are raster scanned across the surface at high speed, having the advantages of being fast, noncontacting and capable of inspecting components of complicated shape and geometry as well as large, plane areas. A pre-prototype has demonstrated successfully the detection of coating thickness variations, disbands and thermal properties variations in a wide range of coatings, and spray parameter variations in plasma sprayed coatings. The optical resolution can be down to 50 um. The choice of laser can be compatible with optical fibre transmission (such as the neodymium yttrium aluminium garnet (Nd:YAC) laser), ensuring minimal inspection head dimensions. The technique is particularly suitable to automated on line inspection of coated products at an early stage in the manufacturing process, and to inspection of components during maintenance or overhaul.
A new approach to modelling of the processes in thermodynamically non-equilibrium systems with particular application to carbon dioxide lasers was developed. This includes the calculation of vibrational temperatures based on Landau-Teller equations, solution of the Boltzmann equation, the equation for the electron diffusion in turbulent plasma and magnetohydrodynamic equations.
Numerical results were validated against experimental measurements. The developed code can be generalized for modelling of other plasma related processes such as welding, chemical vapour deposition, radio-frequency discharges and others.
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