Johan Merzouki, a doctoral student at LaBoMaP, will defend his dissertation on Tuesday, June 19, 2018, on "thestudy thermomechanical loads induced by the tightening of the borehole during drilling of Ti6Al4V under cryogenic assistance".
Members of the jury
- Nathalie TRANNOY-ORBAN, University Professor, UFR SEN, University of Reims Champagne-Ardenne, rapporteur
- Yann LANDON, Associate Professor, ICA, University of Toulouse, rapporteur
- Gilles DESSEIN, University Professor, LGP ENIT, University of Toulouse, examiner
- Gérard POULACHON, University Professor, LaBoMaP, Arts et Métiers, examiner
- Frédéric ROSSI, Associate Professor, LaBoMaP, Arts et Métiers, examiner
- Yessine AYED, Associate Professor, LAMPA, Arts et Métiers, examiner
- Guillaume ABRIVARD, Engineer and Ph.D., Airbus, guest speaker
Summary
Due to the major economic and environmental challenges that the aerospace industry has faced for several decades, the mass fraction of composites in aircraft construction has steadily increased: it was approximately 5% in 1972 for the Airbus A300 and rose to over 50% in 2013 for the Airbus A350. Indeed, with the goal of continuously reducing aircraft weight, the aluminum alloys that previously made up the vast majority of aircraft (75% of the mass in the 1970s), have been gradually replaced by other materials with specific mechanical properties deemed more advantageous, particularly CFRP (Carbon Fiber Reinforced Plastic), which is often combined with titanium alloys because they demonstrate better thermal and electrochemical compatibility than the CFRP/aluminum alloy combination.
As a result, many current assemblies consist of hybrid CFRP/Ti6Al4V laminates, where the goal is to be able to drill the material in a single operation, as was previously the case with metal-to-metal assemblies. Studies conducted on the drilling of these hybrid stacks have shown that the high cutting temperatures during the operation—primarily due to the machining of the Ti6Al4V component—were a major cause of non-compliance with aerospace specifications. It was based on these findings that the idea of using cryogenic assistance was born: cooling the cutting zone by injecting liquid nitrogen through the spindle center, instead of using more conventional lubrication and cooling methods.
In fact, the latent heat absorbed by liquid nitrogen as it vaporizes makes it an excellent choice for efficiently cooling the cutting zone. Its use is also a completely eco-friendly solution, as it eliminates the need for cutting fluids, thereby avoiding the need to wash parts, remove chips, and recycle fluids, all while remaining safe for both the operator and the planet.
This thesis project therefore focuses on studying the effects of cryogenic assistance on the drilling of Ti6Al4V, with a particular emphasis on its impact on the hole shrinkage phenomenon. In fact, the thermomechanical loads induced by the operation, as well as the final shapes and dimensions of the drilled holes, are in reality strongly linked to this phenomenon, which until now has been studied very little. Consequently, this thesis aims, on the one hand, to highlight the importance of hole shrinkage during the drilling of Ti6Al4V and, on the other hand, to provide insights into and a better understanding of this phenomenon under both dry machining and cryogenic-assisted machining conditions.
Practical information
Arts et Métiers Campus- Rue Porte de Paris - 71250 Cluny
Thesis Defense: Tuesday, June 19, 2018 - 2:00 PM - Lecture Hall 2
