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Etude spectroscopique des plasmas de soudage laser: application au transfert d'énergie

Abstract : The work presented here gives the characteristics of the laser induced-plasma plume created during laser welding. First, in the experimental part of the study, we have used the emission spectroscopy to determinate the electron temperature and the density of the plasma. Several tests have been achieved. We have estimated the influence of welding parameters such as : the laser power, the nature of the shielding gas, the pulse duration. These measurements have been achieved on stainless steel, but also on pure metals (Fe, Cr, Ni, Mo, Nb). The emission spectroscopy is used to analyse the welding defects, in order to achieve real time control of the process. Experiments have shown that geometrical and chemical (grease) defectiveness can be detected. The second part of this work is devoted to the numerical model used to describe the laser-plasma interaction. Several models are presented. The calculation of the partition function of each element of the plasma plume allows the theoretical determination of the densities. Then we can estimate the optical properties of the plume (absorption coefficient and refractive index). Electron microscopy measurements of the plasma plume deposits show the presence of sma1l particles. Consequently, we apply the Mie's theory in arder to study the laser beam scattering in the plume. Finally, we model the radiative transfer in the plasma using a discrete ordinate scheme. The numerical results point out the major effect of the scattering on the temperature field in the plume. This model can be used in complement of those calculating the geometry of the weld seam.
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  • HAL Id : tel-01747113, version 1

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David Lacroix. Etude spectroscopique des plasmas de soudage laser: application au transfert d'énergie. Autre [cond-mat.other]. Université Henri Poincaré - Nancy 1, 1997. Français. ⟨NNT : 1997NAN10210⟩. ⟨tel-01747113⟩

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