Improving Global Quality of Life

4 Needs and challenges in welding and joining technologies
4.5 Role and potential of modelling
Advances in the development of welding processes and techniques are only possible with a profound
understanding of the mechanisms that underlie the particular processes. In this context, modelling and
simulation are indispensable tools with continuously increasing relevance. Modelling and simulation
help verify the theoretical perception of a process by checking experimental results qualitatively and
quantitatively against corresponding numerical models. With growing computational power, the numerical
approaches become increasingly complex and accurate. Currently, numerical simulation is used on a routine
basis in many fields of welding research, such as modelling weld pool and arc phenomena, microstructure
development during PWHT, simulating residual stresses and hot cracking susceptibility or predicting
hydrogen embrittlement. Recent developments in modelling approaches and computer programmes have
opened the way to new and improved welding procedures.
Recent approaches to modelling weld pool and arc phenomena as well as metallurgical processes during
welding have advanced simultaneously with progress in computer power. The complexity has continuously
increased and it is possible now to quantitatively describe the flow of liquid metal in the weld bead, the
gas flow and energy input from the arc to the weld bead as well as the microstructural and metallurgical
processes during solidification and in the heat affected zone with good accuracy. Figure 4.9 shows two very
successful examples of these modelling activities for the flow pattern of the liquid metal in the weld bead
and the solid-state material flow in friction stir welding.
Considerable progress is evident in the fields of computational weld mechanics. The development of
powerful computer codes based on Finite Elements or Finite Differences to solve the partial differential
equations describing the thermal, mechanical and/or velocity fields in the welding process has opened
the way to a quantitative prediction of component residual stresses. Recent developments also focus on
the development of entire process models starting with the weld input parameters and finishing with a
quantitative prediction of the weld bead shape and the mechanical properties of the final weld.
Figure 4.9 Modelling weld pool dynamics in arc welding (left) and material flow
in friction stir welding (right) (Reproduced courtesy: Institute for Materials Science,
Graz University of Technology, T. DebRoy)
Through Optimum Use and Innovation of Welding and Joining Technologies Improving Global Quality of Life 31