Browsing by Author "Bruncrona, Amanda"

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Modelling positron-lattice interactions of trapped positrons in solids
(2022-12-01) Bruncrona, Amanda
Perustieteiden korkeakoulu | Bachelor's thesis
Nucleation modelling during selective laser melting
(2023-08-22) Bruncrona, Amanda
Perustieteiden korkeakoulu | Master's thesis
Selective laser melting is an additive manufacturing method used to produce three-dimensional objects. Metal powder particles are melted into shapes using a laser as the energy source. The internal grain structure of the resulting metal part is depending on process and material parameters. The process of selective laser melting can be simulated using SimPARTIX. Nucleation is the occurrence of solid particles in a melt that is cooling down. A nucleation model has been implemented into SimPARTIX together with a grain growth method, which both are using a cellular automaton approach. This thesis presents the theory behind nucleation and the models used to simulate selective laser melting. These include Discrete Element Methods, Smoothed Particle Hydrodynamics, and Cellular Automaton. A theoretical approach to grain structure prediction is also presented. The software used is briefly presented along with the methods for analyzing the grain structures. The simulation setup is described and parameters for the nucleation and grain growth methods are retrieved from the literature. Inconel 718 is chosen as the material to be simulated and the relevant material parameters are presented. The nucleation model is verified and its behavior during different temperature gradients and solidification rates is studied. Simulation cases are fit to the grain structure predictions. Simulations of the full selective laser melting process are studied. The maximum nucleation density parameter is shown to have a great impact on the resulting grain structure. The laser power and velocity also seem to impact the grain structure. The heat transfer coefficient of the system and the initial temperature of the system showed no direct impact on the grain structure. The melt pool during selective laser melting simulations is studied and the thermal gradient and solidification rates are calculated. The resulting grain structures are more equiaxed than the theoretical model predicted. The resolution of the simulations could have been improved, as well as the sample size. The computational performance was a limiting factor during the simulations. Lastly, future development proposals are made.