Steady-state thermal model based on new dedicated boundary conditions – application in the simulation of laser powder bed fusion process

Abstract

Analytical and numerical methods have been widely used to predict the melt pool morphology and temperature distribution of thermomechanical processes involving a moving heat source, such as welding or additive manufacturing. Compared to analytical methods (based on the Rosenthal equation), the finite element method (FEM) provides more realistic results because it allows the consideration of more physical phenomena involved in the laser powder bed fusion (LPBF) process. However, its computation time is significantly longer than that of the analytical methods. In this context, this study proposes a new FE thermal model based on a steady-state simulation and analytically inspired boundary conditions to predict the melt pool morphology and temperature distribution. This proposed model possibly considers temperature-dependent material properties, Gaussian distribution of heat source, convective and radiative heat losses, powder-compact transition, enthalpy due to solid-liquid transition, and effect of heat convection in the melt pool, while allowing fast and accurate predictions of the melt pool size and steady-state temperature distribution. Single-track LPBF simulations were carried out for two most used materials (AlSi10Mg and Inconel 718). The melt pool sizes simulated by the proposed model are compared to those of a transient model and experimental results (melt pool morphology), and a relative error of less than 5% was observed for all the numerical and experimental validation tests. Furthermore, it is shown that the proposed boundary conditions allow accurate prediction of the steady temperature distribution, even with a short geometry in the source moving direction, which drastically reduces the computational cost and greatly facilitate the utilization of steady-state model.