Modelling melt pool dynamics in aluminium-to-steel welds performed by friction melt bonding: a challenge addressed with the particle finite element method

Friction Melt Bonding (FMB) allows to weld aluminium and steel plates in a lap-joint configuration. FMB produces a melt pool in the aluminium plate, which is visually inaccessible as it is trapped between the two plates. As the melt pool boundaries are initially unknown and evolve during the process, numerical simulation is essential to support quantitative research on the FMB process or to predict behaviour in out-of-laboratory conditions. To simulate the FMB process, this work proposes a partitioned methodology that combines PFEM (Particle Finite Element Method) and FEM. PFEM is used for modelling the aluminium plate, including phase change and convective flow within the melt pool. FEM, on the other hand, is used for the steel plate and the accompanying equipment, as they do not present complex multiphysics phenomena such as phase change and evolving boundaries. A 2D model was used for the experimental comparison, as numerous simulations were required to set up the thermal model. Results were compared against experimental measurements. A good agreement between numerical and experimental results was achieved, both for the melt pool geometry and the temperature of a thermocouple. In addition, the effect of ignoring the convective flow inside the melt pool was also studied. In this regard, results show moderate differences in melt pool geometries between flowing and a non-flowing melt pool models.