Abstract
In this work we address the problem of numerically simulating the Friction Stir Welding process. Due to the special characteristics of this welding method (i.e., high speed of the rotating pin, very large deformations, etc.) finite element methods (FEM) encounter several difficulties. While Lagrangian simulations suffer from mesh distortion, Eulerian or Arbitrary Lagrangian Eulerian (ALE) ones still have difficulties due to the treatment of convective terms, the treatment of the advancing pin, and many others. Meshless methods somewhat alleviate these problems, allowing for an updated Lagrangian framework in the simulation. Accuracy is not affected by mesh distortion (and hence the name meshless), but the price to pay is the computational cost, higher than in the FEM. The method used here, the Natural Element Method (NEM), presents some interesting characteristics, such as the ease of imposition of essential boundary conditions and coupling with FEM codes. Even more, since the method is formulated in a Lagrangian setting, it is possible to track the evolution of any material point during the process and also to simulate the Friction Stir Welding (FSW) of two slabs of different materials. The examples shown in this paper cover some of the difficulties related with the simulation of the FSW process: very large deformations, complex nonlinear and strongly coupled thermomechanical behaviour of the material and mixing of different materials.
Highlights
Friction stir welding (FSW) is a solid state welding process used to join two pieces of sheet or plate material as aluminium, copper, lead and even some plastics
The sheets or plates are abutted along edge to be welded and the rotating pin is sunken into the sheets/plates until the tool shoulder is in full contact with the sheets or plates surface
The presented results can be considered as very preliminary, and further refinement of the models is needed, we can conclude that the NEM constitutes a valuable tool for the simulation of such a complex forming process
Summary
Friction stir welding (FSW) is a solid state welding process used to join two pieces of sheet or plate material as aluminium, copper, lead and even some plastics It achieves the welding of the pieces by employing a rotating pin and shoulder that provoke both extremely high plastic deformation and a high heat generation. It is schematically represented in figure 1. Consider the introduction of the point in the cloud of nodes Due to this introduction, the Voronoi diagram will be altered, affecting the Voronoi cells of the natural neighbours of. Sibson [5] defined the natural neighbour coordinates of a point with respect to one of its neighbours as the ratio of the cell that is transferred to when adding to the initial cloud of points to the total volume of
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