Adaptive multi-physics finite element-material point method with two-way conversion between elements and particles for metal additive manufacturing

The thermo-fluid-solid coupling problem is crucial to the metal additive manufacturing (AM) process, particularly in terms of build quality. However, it poses significant challenges to the computational efficiency of high-fidelity numerical simulation methods as the localized melt pool moves along with the heat source. In this study, an adaptive multi-physics finite element-material point method with two-way conversion between elements and particles is proposed for the thermo-fluid-solid coupling problem. It employs material points (particles) to discretize the melt pool and the rough surface area of the solidified track, finite elements to solve the remaining areas of the deposits and substrate, and a background mesh for heat transfer of the whole domain. The two-way conversion algorithm is proposed to fully take advantage of the material point method (MPM) for the melt pool thermo-fluid flow with complex free surface and the finite element method for the thermo-solid problem with small deformation. In particular, the particle-to-element conversion algorithm comprises a void mesh that deforms compatibly with finite elements, an efficient scheme for pairing particles and void elements, and a temperature-based conversion criterion to facilitate adaptive conversion. To the best of the authors’ knowledge, it is the first adaptive two-way conversion algorithm for mesh-based methods and particle-based methods. The accuracy and efficiency of the proposed method are demonstrated through a series of numerical examples, showing good agreement with the analytical and experimental data available in the literature. Comparisons with the multi-physics MPM show that the proposed method outperforms the existing method in terms of efficiency. For instance, in the specific cases of thermo-fluid-solid coupling problems, the proposed method achieves an improvement of 712 %–877 % in efficiency while maintaining the solution accuracy comparable to the multi-physics MPM. The proposed method is shown to be a powerful tool for thermo-fluid-solid coupling problems in metal AM, and the two-way conversion algorithm can be straightforwardly extended to other meshfree methods for localized problems, such as welding, metal cutting, and landslides.