Simulation numérique du soudage du TA6V par laser YAG impulsionnel : caractérisation expérimentale et modélisation des aspects thermomécaniques associés à ce procédé

摘要

This work is a part of study which goal is to realize a computer modelling of the thermomechanical phenomena occurring during the YAG pulse laser welding of titanium alloy (TA6V). The filet welding has different heterogeneities (microstructural and mechanical). In fact, the temperature causes microstructural changes (phase transformations, precipitation...) and modifies the mechanical properties. Thermomechanical modelling has thus to be established for the welding of TA6V. In this study, we focus on the identification of the different phase transformations occurring during the welding, during the heating and the cooling. Then we define the conditions for which the mechanical behavior of these different phases has to be characterized in order to obtain the residual stresses and the residual strains of this welded part. A thermometallurgical and mechanical modelling will thus be proposed for the YAG pulse laser welding of TA6V. The behavior of material after laser welding can be described by three fundamental data (field of temperature, metallurgical state and fields of stress/strain). We have identified and modelled the different phenomena and several stages are to be considered : Determination of the metallurgical phase transformations during the deposit of energy and the cooling ; Experimental Characterization of the mechanical behavior of each phase under the purposeful conditions of temperatures and strains ; Modeling of the thermomechanical behavior by a thermo-elasto-viscoplastic law integrating phase transformation, in order to quantify the strains and the residual stresses observed in the assemblies ; Validation of the model with a welding instrumented test