Design and study of SPD processes; HPT and MF

Abstract

This master thesis aims to model the severe plastic deformation through the HPT (High Pressure Torsion) and MDF (Multi Directional Forging) methods in order to determine the necessary external loads. These external loads, see torque and pressure or exerted load, have been calculated through a finite element method and CAE software, and they will be used in a future project to develop a hydraulic torsion press in order to be able to develop the HPT SPD processes in the PROCOMAME (Procesos de Conformado de Materiales Metálicos) group laboratories in the EEBE (Escola d’Enginyeria de Barcelona Est) faculty of the Technical University of Catalonia (UPC). The results show the relation between the numbers of turns, torque, load and the effect of those over the material, illustrating the effective strain and stress accumulated along the process. The accumulated torque data is very promising, and shows a saturation in few turns, giving a reliable constant torque with which a hydraulic and torsion machine would be effectively designed, giving, of course, a safe margin of security. On the other hand, in cooperation with a research group from Autonomous National University of Mexico (UNAM), new state-of-the-art studies have been simulated in terms of a modified HPT processes. The process has the particularity that torsion and compression are applied at the same time, whereas normally pressure is first applied before torsion. The established relationship in México’s machine is 1 turn per 5 mm, and the main objective is to obtain the external loads and if the accumulated effective strain would be enough to process an ultra-fine grain material with the expected material properties. As a previous essay, a mechanical buckling effect is analytically performed beforehand in order to avoid this effect due to the small section as a function of sample length. The obtained results show a new possible method to obtain severe plastic deformation materials with a bigger size than other processes avoiding the plausible buckling effect, which is estimated around 40 and 70 mm for Aluminium 1100 depending on the set-up chosen. Finally, a thermal analysis simulation is performed for the MDF method in order to study the heat flux and its evolution generated along the process and after that, the heat flux dispersion evacuated out of the system. The results show a great concordance with empirical data obtained in a different master thesis developed in parallel inside the same department, reaching to temperatures of 1ºC in the external face of the dies.