Meshfree Simulations for Additive Manufacturing Process of Metals

We present a meshfree direct numerical simulation (DNS) capability for the additive manufacturing (AM) process of metals based on the hot optimal transportation meshfree (HOTM) method. The HOTM method is a meshfree thermomechanical Lagrangian computational framework for material behaviors under extreme thermomechanical loading conditions. It combines the optimal transportation meshfree (OTM) method and the variational thermomechanical constitutive updates. In the HOTM method, the linear momentum and energy conservation equations are solved simultaneously in a monolithic way. A phase-aware constitutive model is developed to predict the melting/solidification phase change of metals and multiphase mixing during the AM process automatically. The HOTM method is validated in the simulations of the laser welding process over Inconel 625 bare plate by applying heat flux models for the laser beam, the convective heat loss, and radiation heat loss. The performance measurements of the simulation results, including the melt pool geometric dimensions and cooling rates, are comparable to the experimental data measured in the AM benchmark tests. The influence of various laser powers and laser scanning speeds on the melt pool thermodynamics is also studied.