Semi-coupled resolved CFD–DEM simulation of powder-based selective laser melting for additive manufacturing

Abstract

We present a semi-coupled resolved Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) to simulate a class of granular media problems that involve thermal-induced phase changes and particle–fluid interactions. We employ an immersed boundary (IB) method to model the viscous fluids surrounding solid particles in conjunction with a fictious CFD domain occupied by the actual positions of the particle. Heat transfers between the actual fluids and the fictitious particle are treated as a multiphase problem by the CFD to resolve the temperature gradient distribution within each granular particle and its possible phase change (e.g., melting or partial melting). The mechanical interactions between the solid particles and the fluids are modeled by coupled DEM and CFD. The proposed method is validated by simulations of a typical powder-based selective laser melting (PB-SLM) process. Three key SLM input parameters, laser power, laser energy distribution and hatch distance, are examined on the effect of melting. The simulation results capture key features and observations of PB-SLM found in experiments and are quantitatively consistent with available testing data. The study provides a physically based, high-fidelity computational approach for future PB-SLM additive manufacturing.