PhD defence of Ahmed Mehdi Roula

– Prof. Pascale Balland, Université Savoie Mont Blanc

– Prof. Carl Labergere, UTT

– Prof. Régis Bigot, ENSAM Metz

– Prof. Katia Mocellin, Mines Paris

– Prof. Pierre-Olivier Bouchard, Mines Paris

 

 

Abstract:

 

The present Ph.D. thesis deals with the sheet flow forming process. This forming process enables to reach large plastic strains due to the compressive and incremental action of the roller. Nevertheless, the lack of geometric accuracy of the produced parts represents a major issue of the process and the main motivation of the present work. The first step was to set up a numerical model of the flow forming process using the finite element software FORGE®. Multiple appropriate mechanical characterization tests associated with constitutive models adapted to the process conditions enabled to enhance the material behavior description during the process modeling. In a second step, a finite element analysis using the numerical model allowed understanding the complex material flow during the forming operation. This led to the explanation of defects presence. Finally, practical developments were established in order to control the flow formed geometries within a wide range of reduction ratios. A finite element analysis was also conducted to predict the fracture limit of the studied material for the flow forming process.

 

Keywords: Sheet flow forming, necking, mechanical characterization, finite element modeling, incremental processes