Discrepancies between Gaussian surface heat source model and ray tracing heat source model for numerical simulation of selective laser melting

Selective laser melting (SLM) is one of the most promising technologies in metal powder additive manufacturing. Over the past few decades, high-fidelity thermo-fluid simulations have been extensively used to understand the physical mechanisms of the SLM process. However, there are few existing simulation frameworks that can accurately reproduce the complex interactions between laser beams and powder particles, which significantly contribute to the energy flux during the whole manufacturing process. In this work, a high-fidelity, multiphase multi-physics simulation framework with the ray tracing heat source model is developed to better simulate the laser-matter interactions and melt pool dynamics during SLM. In this simulation framework, the gas-metal interface is captured by a sharp surface capturing technique (isoAdvector) and modeled by a geometrical surface reconstruction step. With the incorporation of a ray tracing heat source, the discretized laser rays can impinge on the reconstructed gas-metal interfaces and undergo multiple reflections. Moreover, simulations with ray tracing heat source and Gaussian surface heat source dealing with different structures were performed and compared. We show that the structures with more sheltered surfaces (by adjacent structures) or larger self-shielding degrees will lead to larger discrepancies between the simulation results with these two heat source models. Such observations can guide the choice of heat source models when modeling structures with different complexities.