NUMERICAL SIMULATION OF A COMBINED WELDING-BRAZING PROCESS. APPLICATION TO AN ALUMINUM-TITANIUM HETEROGENEOUS ASSEMBLY

摘要

In this study, an heterogeneous Ti/Al assembly isproposed for the built of aircraft structures. This kindof structure combines advantages of both materials:the aluminum is light-weight and less expensivewhereas the titanium offers superior mechanicalproperties. A welding - brazing assembly in overlapconfiguration is studied. The two selected materialsare the aluminum alloy Al5754 and the quasi-puretitanium Ti40. The aluminum is fused by laser ontitanium (solid) and the joining is obtained by theformation of a ceramic intermetallic compound(TiAl3) along the Ti/Al interface. The size of theintermetallic layer has a significant effect on themechanical strength of the assembly. The effects ofprocess parameters on the geometrical properties ofthe assembly are investigated by numericalsimulation (finite element method) and experimentalvalidation. More precisely, the effects of the thermalfield and of the fluid flow are correlated to the size ofthe intermetallic layer in an axisymmetric particularcase.The numerical problem is implemented with thecommercial software Comsol Multiphysics™, bycoupling heat equation, Navier-Stokes equation andthe free boundary motion. The latter is treated withthe Arbitrary Lagrangian Eulerian method and with aparticular focus on the contact angle implementation.An experimental validation of the model is realizedwith a TRUEDISK 10002 laser.