Contribution au développement d’une méthode de prédiction de la géométrie multi-échelle des pièces polies par tribofinition

Abstract

This thesis is based on the context of roughness reduction of Inconel718 parts produced by additive manufacturing (SLM) using the drag finishing technique. The objective was to understand the mechanisms of action of the abrasive media on the surfaces to polish. In addition, the complexity and high added value of the parts produced by additive manufacturing, combined with the small-scale production context, implies a major need for modelling to predict the optimal processing conditions. As the high roughness levels of SLM parts lead to long processing times to reach the specified roughness, the challenge of applying the drag finishing process to polish parts is actually to predict the evolution of the shape of the parts. Thus, this thesis focused on the development of a modelling tool (at the macroscopic scale) of the action of abrasive media flow (considered as a continuum) around a part to be treated. ALE and CEL models of this fluid-structure interaction have been developed. To feed these simulations, a method for characterising the rheological properties of the media was proposed, inspired by the techniques used with geomaterials in civil engineering. This method, known as “triaxial test”, showed the importance of the geometry of an elementary media on the rheological behaviour of the bulk media. In fact, the numerical model allowed to quantify the effect of the media type on the mechanical action induced around the part (normal and tangential stresses, sliding velocity). These local physical parameters allowed us to set up a method for predicting the evolution of the geometry of the part (i.e. the wear of the part). At the mesoscopic scale, these physical parameters also provided a better understanding of the mechanisms of media reagarding the angle of incident on the surface, and in particular whether material removal or plastic deformation was dominant.