Champs thermiques et mécaniques induits par le mouvement des dislocations

Abstract : In the context of the modelling of materials behaviors, it is difficult to ignore the irreversible processes. These processes are inseparably connected with inelastic or anelastic deformations and therefore with intrinsic dissipation which leads to an overheating of the solid. In practice, these deformations are associated with the propagation of the lattice defects. A thermodynamical analysis of this phenomena shows that the heat source may be represented by the motion of defects causing an important thermal gradient. In this work, we treated the dissipative effects and the thermoelastic coupling mechanisms associated with the moving dislocations. This is done in a general framework but is used to study the thermomechanical effects of the steady-state quasi-static motion of a straight edge dislocations in an elastic medium. To analyse the thermomechanical effects associated with the moving dislocations, we used the irreversible thermodynamic process. We shown that the existence of a moving dislocation in a medium behaves likes a moving and dissipative straight heat source. This source generates a thermal variations which in turn generate thermal strains and stresses. The analysis of these fields shows that the thermomechanical coupling caused by the moving dislocation remains negligible. Nevertheless, the extension of this study to a situation of a large number of dislocations like a shear band allowed to obtain an important thermal effect. Morever, the thermodynamical study permitted to introduce a thermodynamical force associated with the moving dislocation. The calcul of this force from the different thermomechanical fields introduced by the presence and movement of the dislocation allowed to establish that whatever the speed of the dislocation and the radius of her core, this force is exactly the Peach and Koehler one and it's never due to the proper thermomechanical fields of the straight edge dislocation
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Abderrahim Sqalli Houssaini. Champs thermiques et mécaniques induits par le mouvement des dislocations. Autre. Université Paul Verlaine - Metz, 1996. Français. ⟨NNT : 1996METZ005S⟩. ⟨tel-01777107⟩

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