Simulative prediction of the manufacturing process in wire-arc additive manufacturing (WAAM) (T03#)

• Subject Area: Joining and Separation Technology ; Fluid Mechanics ; Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: from 2022 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 236616214

Additive manufacturing holds enormous potential for the future development of the metal processing industry. In particular, the modification of low-cost semi-finished products by individualized structures expands the manufacturing possibilities and increases flexibility and cost-effectiveness in small series. In the field of welding technology research, the development of GMAW process variants for additive manufacturing is currently being increasingly considered (WAAM - wire arc additive manufacturing). This makes it possible to produce metallic components with different topologies directly from the molten metal. It implies that the topology of the substrate is determined during the process by the process itself. A key to the efficient development of an additive manufacturing chain is therefore the availability of mathematical models that enable digital precalculation of the necessary process steps. In particular, this requires a physics-based numerical model of the welding process used. Approaches to this already exist in the field of joint welding, but have not yet been transferred to the additive manufacturing of structures. This will be done in the proposed transfer project with a novel approach, which is expected to solve the numerical problem with reasonable computational effort in the future. In SFB1120, the relationship between molten pool flows during gas metal arc welding and the resulting weld geometry is being researched. So far, the hydrodynamic equations of the molten pool flows have mainly been solved using the Euler approach, where the computational mesh discretizes the entire space of the simulation domain. This approach is particularly well suited for the numerical study of the physical effects of conventional GMA welding, where a linear motion of the torch on a flat plate can be assumed. However, this approach encounters limitations with the dynamic growth of the component geometry, as is the case in the WAAM process. The level-set or VOF methods used in the Euler approach also require the discretization of the entire space, which results in inefficiencies in terms of computational effort, especially for complex component geometries, even when using adaptive meshing strategies. This is contrasted with the SPH approach (smoothed particle hydrodynamics), in which only the considered mass of the material is discretized rather than the entire space of the simulation domain. In order to verify the applicability of the SPH method to the simulation of the MSG welding process, a case study was initiated as an accompaning project within the SFB1120 to confirm transferability to the MSG process. The project described here enables the transfer of the methods, which have so far been used exclusively in the field of basic research, to the field of industrially relevant application-oriented models.

• DFG Programme: Collaborative Research Centres (Transfer Project)
• Subproject of: SFB 1120: Precision manufacturing by controlling melt dynamics and solidification in production processes
• International Connection: Austria, Belgium
• Applicant Institution: Rheinisch-Westfälische Technische Hochschule Aachen
• Business and Industry: Fronius International GmbH; Guaranteed B.V.
• Project Head: Professor Dr.-Ing. Uwe Reisgen