International Journal for Computer-
Aided Engineering and Software
Vol. 27 No. 8, 2010
# Emerald Group Publishing Limited
Received 22 July 2009
Revised 2 March 2010
Accepted 18 March 2010
Multi-physics simulation of
friction stir welding process
Robert Hamilton, Donald MacKenzie and Hongjun Li
Department of Mechanical Engineering, University of Strathclyde,
Purpose – The friction stir welding (FSW) process comprises several highly coupled (and non-linear)
physical phenomena: large plastic deformation, material flow transportation, mechanical stirring of
the tool, tool-workpiece surface interaction, dynamic structural evolution, heat generation from
friction and plastic deformation. This paper aims to present an advanced finite element (FE) model
encapsulating this complex behaviour and various aspects associated with the FE model such as
contact modelling, material model and meshing techniques are to be discussed in detail.
Design/methodology/approach – The numerical model is continuum solid mechanics-based, fully
thermo-mechanically coupled and has successfully simulated the FSW process including plunging,
dwelling and welding stages.
Findings – The development of several field variables are quantified by the model: temperature,
stress, strain. Material movement is visualized by defining tracer particles at the locations of interest.
The numerically computed material flow patterns are in very good agreement with the general
findings from experiments.
Originality/value – The model is, to the best of the authors’ knowledge, the most advanced
simulation of FSW published in the literature.
Keywords Welding, Mathematical modelling, Finite element analysis, Joining processes
Paper type Research paper
Friction stir welding (FSW) provides a new technique for metal joining and processing, in
which a rotating tool, with a particularly designed shape, is first inserted into the adjoining
seams of the components to be welded and then travels all along the welding line. Since its
inception FSW has attracted worldwide interest. The FSW process comprises of several
highly coupled (and non-linear) physical phenomena: large plastic deformation, material
flow transportation, mechanical stirring of the tool, tool-workpiece surface interaction,
dynamic structural evolution, heat generation from friction and plastic deformation, etc.
Briefly, thermal and mechanical behaviours are mutually dependent and coupled together.
Full multi-physics analysis is therefore required to incorporate all the physics phenomena
so as to simulate the process as close to the real FSW process as possible.
The FSW process has been investigated numerically by several researchers. Ulysse
(2002) presented a three-dimensional (3D) visco-plastic model, using the commercial
software FIDAP (1994). The heat generation was determined as the product of the
effective stress and effective strain rate. In the model, the tool rotates and the plates are
fed toward the tool. A constant tangential velocity on the tool surface is specified to
simulate the rotation of the tool, assuming some velocity slip at the contact surface. The
transverse movement of the workpiece was modelled by prescribing a velocity boundary
condition on the incoming side of the workpiece. As only the heat from deformation
energy dissipation was accounted for, a thermal contact conductance can be applied at
the interface to study the heat transfer between the tool and workpiece. It was concluded
that the measured temperatures were consistently overpredicted by the model and the
discrepancies probably resulted from an inadequate representation of the constitutive
behaviour of the material used in FSW.
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