Substepped and advected subdomain methods for part-scale LPBF modeling

This work presents substepping schemes for part-scale Laser Powder Bed Fusion (LPBF) modeling where the computational domain is divided into a fast partition with a small time-step and a slow one using a large time-step. These schemes are of special interest due to the disparity of time scales present in LPBF applications, which renders simulation prohibitively expensive unless simplifications are made. A Robin–Robin substepper is proposed and compared to the scheme proposed by Hodge (2021). Additionally, the introduction of an advected subdomain in the fast partition is proposed. This approach was first presented in Slimani et al. (2024) and allows for larger time-steps, as the problem in the Heat Affected Zone (HAZ) is posed in the moving reference frame of the laser, where the thermal field is significantly steadier than in the fixed frame. These methods are used in combination to obtain a computationally efficient scheme for LPBF thermal simulations. The proposed methods are implemented in FEniCSx. Their strengths and weaknesses are evaluated through 2D benchmarks, comparison with experimental melt pool data, and 3D LPBF simulations.