Abstract
Molten metal melt pools are characterised by highly non-linear responses, which are very sensitive to imposed boundary conditions. Temporal and spatial variations in the energy flux distribution are often neglected in numerical simulations of melt pool behaviour. Additionally, thermo-physical properties of materials are commonly changed to achieve agreement between predicted melt-pool shape and experimental post-solidification macrograph. Focusing on laser spot melting in conduction mode, we investigated the influence of dynamically adjusted energy flux distribution and changing thermo-physical material properties on melt pool oscillatory behaviour using both deformable and non-deformable assumptions for the gas-metal interface. Our results demonstrate that adjusting the absorbed energy flux affects the oscillatory fluid flow behaviour in the melt pool and consequently the predicted melt-pool shape and size. We also show that changing the thermo-physical material properties artificially or using a non-deformable surface assumption lead to significant differences in melt pool oscillatory behaviour compared to the cases in which these assumptions are not made.
Highlights
Laser melting is being utilised for material processing such as additive manufacturing, joining, cutting and surface modification
To verify the reliability and accuracy of the present numerical simulations, the melt-pool shapes obtained from the present simulations, for the problem introduced in section 2.1, are compared to experimental observations reported by Pitscheneder et al [18]
We extended this study and performed a high-fidelity simulation based on the large eddy simulation (LES) turbulence model and took the effects of surface deformations into consideration [44] and showed that for the conduction-mode laser melting problem we considered, the influence of surface oscillations on melt pool behaviour is larger compared to the effects of turbulent flow in the melt pool; the results do not agree with experiments without using some enhancement
Summary
Laser melting is being utilised for material processing such as additive manufacturing, joining, cutting and surface modification. The results of experimentation performed by Ayoola et al [1] revealed that the energy flux distribution over the melt-pool surface can affect melting, convection and energy transport. In liquid melt pools and the subsequent re-solidification during laser melting processes. The imposed energy flux heats and melts the material and generates temperature gradients over the melt-pool surface. The resulting surface tension gradients and Marangoni force is often the dominant force driving fluid flow, as can be understood virtually from the numerical investigation conducted by Oreper et al [2] and experimental observations reported by Mills et al [3]. Experimental investigations of Heiple et al[4] showed that the presence of surfactants in molten materials can alter Marangoni convection in the melt pool, and the melt-pool shape.
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