Computational analysis of inter-material mixing and weld-flaw formation during dissimilar-filler-metal friction stir welding (FSW)

Abstract

Purpose

Friction stir welding (FSW) butt-joining involving the use of a dissimilar filler metal insert between the retreating and advancing portions of the workpiece is investigated computationally using a combined Eulerian-Lagrangian (CEL) finite element analysis (FEA). The emphasis of the computational analysis was placed on the understanding of the inter-material mixing and weld-flaw formation during a dissimilar-material FSW process. The paper aims to discuss these issues.

Design/methodology/approach

The FEA employed is of a two-way thermo-mechanical character (i.e. frictional-sliding/plastic-work dissipation was taken to act as a heat source in the energy conservation equation), while temperature is allowed to affect mechanical aspects of the model through temperature-dependent material properties. Within the analysis, the workpiece and the filler-metal insert are treated as different materials within the Eulerian subdomain, while the tool was treated as a conventional Lagrangian subdomain. The use of the CEL formulation within the workpiece insert helped avoid numerical difficulties associated with excessive Lagrangian element distortion.

Findings

The results obtained revealed that, in order to obtain flaw-free FSW joints with properly mixed filler and base materials, process parameters including the location of the tool relative to the centerline of the weld must be selected judiciously.

Originality/value

To the authors’ knowledge, the present work is the first reported attempt to simulate FSW of dissimilar materials.

Citation

Grujicic, M., Yavari, R., Ramaswami, S., Snipes, J. and Galgalikar, R. (2015), "Computational analysis of inter-material mixing and weld-flaw formation during dissimilar-filler-metal friction stir welding (FSW)", Multidiscipline Modeling in Materials and Structures, Vol. 11 No. 3, pp. 322-349. https://doi.org/10.1108/MMMS-12-2014-0062