Linking a CFD and FE analysis for Welding Simulations in Ti-6Al-4V

Finite element (FE) modelling of fusion welding methods has become an established numerical tool used by high-value manufacturing industries and academic communities, largely due to its capabilities to predict residual stress and distortion. However, a major drawback of this type of approach is the requirement to perform a test weld at the relevant process parameters, geometry and material to understand the size and shape of the weld pool formed. With this knowledge a priori the FE model can then be used to best-fit the thermal cycles to the part, and from the thermal field predict the mechanical response to this thermal loading. This well-established method of FE simulation reduces the predictive capabilities of the model. Thus, an improved method of using a different modelling strategy to feed the thermal cycles in to the FE model is desirable. A computational fluid dynamics (CFD) modelling capability has been developed which is able to predict not just weld pool shape, but using real physical phenomena such as surface tension and thermo-capillary forces, buoyancy forces and interfacial phenomena between solid-liquid and liquid-gas phases, can predict thermal fluid flow lines within the molten region, the presence of regions susceptible to porosity and the formation of the keyhole phase, containing metallic vapor. Using simplistic Cartesian co-ordinates the fusion boundary can be extracted from CFD analysis for entry in to an FE model for structural analysis in terms of residual stress and distortions. Therefore, the modelling approach predicts both fluid type and structural type properties of the transient welding operation.