Within the scope of the joint research project with the Chair of Aerodynamics (TUM) the mechanisms of action during laser beam melting are investigated. Laser beam melting is an additive manufacturing process in which several physical processes such as thermofluid dynamics, light-matter interaction and phase transitions occur simultaneously. In this research project the complex interaction of the physical mechanisms is to be investigated experimentally and with the help of a numerical modelling approach.
Laser beam melting is a generative manufacturing process which serves for the tool-free production of metallic components with special geometric features. With local melting of the metal powder by a laser beam and the subsequent solidification of the material, the component can be built up in layers. Tools and moulds made of metal with integrated cooling and tempering channels cannot be produced in this way using classic production technologies. In addition to its use in prototype construction, laser beam melting is also increasingly used in series production. Identifying and quantifying the basic process mechanisms of this manufacturing process is of the highest priority for future applications.
Objective of the project
The thermal, mechanical and fluid dynamic processes are to be analysed using experimental techniques such as high-speed or thermographic recordings of the melt pool. The determined data should contribute to an increased understanding of the process. At the same time, the Chair of Aerodynamics (TUM) is developing a numerical simulation model for process simulation which predicts the temperature field, the residual stresses, and deformations in the components induced by the heat source. Experimental findings are to be incorporated into the simulation model and also serve to validate the simulation results.
First, the mechanisms of action and influencing variables relevant for laser beam melting are determined. The next step is a selection of suitable experimental procedures. Since metallographic examinations, micrographs or CT images of the specimens only provide a limited insight into the processes during the laser beam melting process, suitable experimental methods for dissolving the transient processes must be identified. In this way, defects can not only be detected, but an understanding of their origin can be created. Suitable exposure lasers, which are aligned on-axis as well as off-axis to the laser beam, provide an insight into process parameters such as the length and width of the molten pool, the velocity distribution of the powder particles, and the formation of splashes and ejections from the molten pool. Mesh-free methods (also called "Smoothed Particle Hydrodynamics" SPH) are used in numerical modelling and development. Among other things, the powder bed as well as the fluiddynamic and thermodynamic processes are to be modelled. A comparison of the SPH method with a typical Euler (grid-based) method provides an interesting insight and also serves to validate the simulation results. Finally, the simulation models are validated experimentally, whereby the investigations of the laser beam melting processes are to be carried out with the same process parameters in each case.
The ProSim research project is funded by the German Research Foundation (DFG) (project number 387081806). We would like to express our sincere thanks for this.