Effets du défaut caniveau sur la concentration de contrainte au sein de joints soudés par laser en alliage d’aluminium AA6005-T6

Abstract

Given to their mechanical properties, the aluminium alloys are more and more used for building train cars body. Furthermore, laser welding is a process which offers very interesting results combined with high production frequencies. As a result, using both would be a very powerful mean to decrease the production costs in railway construction industry. Bombardier Transport, now acquired by Alstom, has become a leader in using this promising combination. A large field of standards regulates the defects in the laser welded joints. Nevertheless, these standards has a detrimental impact on the productivity of this method and the need of developping a new internal standard has emerged, which could improve the effectiveness without being nefast to the security. The study has been done on the defect named « undercut » in the DIN EN ISO 13919-2. Numerical simulations has been done around the critical values given in the standard. This would higlight the impact on the stress concentration factor that could have some variations in the shape of the undercut. Furthermore, a method for measuring the depth, the width and the radius of curvature of the defects, as fast and precise as possible has been worked out to improve the simulations and simulate more shapes regarding to the ones of the defects on real laser welded joints. A computed theoretical model of the Kt has been proposed. Finally, several fatigue tests has been done to validate the hypothesis concerning the location of the fracture initiation at the maximum stress concentration zones and search the linked between the shape of the defect and the fatigue life, also by analysing the fracture surfaces.

Date	17 Aug 2021
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Philippe Bocher (Supervisor) & Vincent Demers (Co-supervisor)