| Abstract | Laser Powder Bed Fusion (LPBF) is a 3D printing process using metal powder as the raw material. A laser selectively melts the powder bed, and the raw material is consolidated using a layer-by-layer building strategy. At the melt pool scale, solid-liquid phase change, surface tension and evaporation effects are involved, and their highly dynamic interaction drives the melt pool (MP) morphology, thermal history, and the occurrence of defects in the final part. To predict the latter, high fidelity thermo-fluid models are currently used. However, precise knowledge and quantification of the model errors and their sources is absent as verification and validation are either disregarded or incomplete. This hinders meaningful insight from the current LPBF MP predictions.
This work proposes a reproducible quantitative benchmark to evaluate the accuracy and adequacy of LPBF MP scale models. It is twofold: verification via a code-to-code comparison and validation with experimental data. It focuses on the static irradiation of a bare plate of Ti-6Al-4V, experimentally studied by Cunningham et al.
The code-to-code comparison of results is performed using selected high-fidelity thermo-fluid models. Space and time refinement studies are proposed to analyze the sensitivity of the solution to the chosen discretization. Targeted verification metrics are the MP and vapor depression (VD) dimensions, and temperature gradients. Monitoring of the error norms assesses if the different thermo-fluid models converge to the same reference solution, defined as the solution obtained with the finest discretization. The second part of the benchmark assesses the models' adequacy using Cunningham et al. experimental results. This validation step focuses on the temporal evolution of the MP and VD dimensions, and we are interested in the predictive capacity of the models for the different melting modes encountered in the experimental setup.
The presentation focuses on the benchmarking of two diffuse finite-element based thermo-fluid frameworks, developed by independent groups: Lethe from Polytechnique Montréal, and MeltPoolDG from the Technical University of Munich. It also aims to advertise this new benchmark to other research groups and encourage them to verify and validate their thermo-fluid models using the proposed studies. Hence, it provides the required numerical results to compare their own solutions. Special care is taken to thoroughly describe the benchmark case, material properties, and solver parameters ensuring reproducibility |
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| References | - Cunningham, Ross, Cang Zhao, Niranjan Parab, Christopher Kantzos, Joseph Pauza, Kamel Fezzaa, Tao Sun, and Anthony D. Rollett. ‘Keyhole Threshold and Morphology in Laser Melting Revealed by Ultrahigh-Speed x-Ray Imaging’. Science 363, no. 6429 (22 February 2019): 849–52. https://doi.org/10.1126/science.aav4687.
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