Abstract

The Friction Stir Spot Welding (FSSW) process involves large deformations in the neighborhood of the tool. The simulation of this process has to account for a pasty phase in which the material is stirred, and a phase remaining solid. An Arbitrary Lagrangian Eulerian (ALE) approach combined with respectively fluid and solid behaviours in each of those phases may allow to simulate a lot of rotations of the tool into the material while following the boundaries of the sheets. This work focuses on a first stage of this study, the development of a mixed formulation temperature/velocity/pressure of a fluid finite element P1+/P1 in the unsteady case.

Highlights

  • The Friction Stir Spot Welding process (Sakano et al, 2001) is derived from the Friction Stir Welding process (Thomas et al, 1991) which consists in creating a point weld between two sheets by penetration of a rotating tool into the material

  • We describe here the formulation of the P1+/P1(Arnold et al, 1984) fluid finite element with thermomechanical coupling

  • The P1+/P1 fluid finite element developped in the framework of a mixed formulation temperature/velocity/pressure is here extended to the unsteady case

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Summary

Introduction

The Friction Stir Spot Welding process (Sakano et al, 2001) is derived from the Friction Stir Welding process (Thomas et al, 1991) which consists in creating a point weld between two sheets by penetration of a rotating tool into the material. The arbitrary motion will be set in such a way that the mesh will follow material points in the solid phase but not in the mushy zone This will enable us to simulate important rotations of the tool while following the boundaries of the sheets, including the formation of a bead around the tool and the interface between both phases during the process. We describe here the formulation of the P1+/P1(Arnold et al, 1984) fluid finite element with thermomechanical coupling It has already been implemented (Feulvarch et al, 2005; Feulvarch et al, 2007) in the code SYSWELD (2007) in a thermomechanical version for steady states, and is here extended to the unsteady case with a temperature/velocity/pressure formulation. In which p is the current extremal node number, b refers to the bubble node and λ is the vector of degrees of freedom of the bubble node, homogeneous to velocities

Weak form
Discretization
Introduction of an extra approximation
Unsteady mechanical resolution
Unsteady mechanics
Conclusion
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