Friction stir welding (FSW) process is a solid‐state joining process during which materials to be joined are not melted. As a consequence, the heat‐affected zone is smaller and the quality of the weld is better with respect to more classical welding processes. Because of extremely high strains in the neighborhood of the tool, classical numerical simulation techniques have to be extended in order to track the correct material deformations. The Arbitrary Lagrangian–Eulerian (ALE) formulation is used to preserve a good mesh quality throughout the computation. With this formulation, the mesh displacement is independent from the material displacement. Moreover, some advanced numerical techniques such as remeshing or a special computation of transition interface is needed to take into account non‐cylindrical tools. During the FSW process, the behavior of the material in the neighborhood of the tool is at the interface between solid mechanics and fluid mechanics. Consequently, a numerical model of the FSW process based on a solid formulation is compared to another one based on a fluid formulation. It is shown that these two formulations essentially deliver the same results in terms of pressures and temperatures.

The particle finite element method (PFEM) is a Lagrangian method that avoids large mesh distortion through automatic remeshing when the computational grid becomes too distorted. The method is well adapted for flows with deforming interfaces and moving boundaries. However, the \(\alpha \)-shape technique used to identify these boundaries presupposes a mesh of approximately uniform size. Moreover, the \(\alpha \)-shape criterion is purely geometric and, thus, leads to violations of mass conservation at boundaries. We propose a new algorithm for mesh refinement and adaptation in two dimensions to improve the ratio accuracy to computational cost of the PFEM. A local target mesh size is prescribed according to geometric and/or physics-based criteria, and particles are added or removed to approximately enforce this target mesh size. Additionally, the new boundary recognition algorithm relies on the tagging of boundary nodes and a local \(\alpha \)-shape criterion that depends on the target mesh size. The method allows thereby reducing mass conservation errors at free surfaces and improving the local accuracy through mesh refinement and simultaneously offers a new boundary tracking algorithm. The new algorithm is tested on four two-dimensional validation cases. The first two cases, i.e., the lid-driven cavity flow at Reynolds number 400 and the flow around a static cylinder at Reynolds numbers below 200, do not feature a free surface and mainly illustrate the mesh refinement capability. The last two test cases consist in the sloshing problem in a reservoir subjected to forced oscillations and the fall of a 2D liquid drop into a tank filled with the same viscous fluid. These last two cases demonstrate the more accurate representation of the free surface and a corresponding reduction of the error in mass conservation.

A simulation method is developed herein based on the particle finite element method (PFEM) to simulate processes with surface tension and phase change. These effects are important in the simulation of industrial applications, such as welding and additive manufacturing, where concentrated heat sources melt a portion of the material in a localized fashion. The aim of the study is to use this method to simulate such processes at the meso-scale and thereby gain a better understanding of the physics involved. The advantage of PFEM lies in its Lagrangian description, allowing for automatic tracking of interfaces and free boundaries, as well as its robustness and flexibility in dealing with multiphysics problems. A series of test cases is presented to validate the simulation method for these two effects in combination with temperature-driven convective flows in 2D. The PFEM-based method is shown to handle both purely convective flows and those with the Marangoni effect or melting well. Following exhaustive validation using solutions reported in the literature, the obtained results show that an overall satisfactory simulation of the complex physics is achieved. Further steps to improve the results and move towards the simulation of actual welding and additive manufacturing examples are pointed out.

This paper presents recent investigations in Micro-Plasto-Hydrodynamic (MPH) lubrication. Industrial evidences of the existence of MPH lubrication mechanism for cold rolling processes are presented. A new lubrication model developed for strip drawing processes is then applied to predict the MPH lubrication initiation and MPH lubrication extension along the tool-piece solid contacts initially in boundary lubrication regime. Finally, it is shown how this new MPH lubrication model can be implemented in a cold rolling model to maximize mills capabilities, determine optimum rolling oils properties and predict roughness transfer.