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