Heat transfer model and finite element formulation for simulation of selective laser melting additive manufacturing

Abstract

Selective laser melting (SLM) is a type of additive manufacturing (AM) process that involves direct manufacturing by locally melting and binding of metallic powder using a guided laser beam. Rapid manufacturing processes like SLM provides the ability to produce low-volume, customized meal parts with complex geometries relatively quickly at a moderate cost. The barrier to the adoption of SLM is the inability to predict material properties for any given process and thus it is required to develop an automated simulation tool for modeling SLM. In this work, a novel approach and finite element formulation for modeling the melting, consolidation and re-solidification that occurs in SLM is presented. Two state variables to track the phase and the amount of consolidation is introduced. The material properties and the heating of the material naturally varies due to the densification of the powdered metal. A Lagrangian finite element formulation is derived, which solves for the governing equations on the unconsolidated reference configuration. A transient fully implicit integration algorithm is used allowing for relatively larger time steps without loss of accuracy. The finite element model is implemented into a general-purpose parallel finite element solver Albany developed by the Computational Mechanics Department at Sandia National Laboratory integrated with Simmetrix meshing and capable of running on parallel high-performance computing platforms. Results are presented compared to experimental results in the literature for a linear laser track and a single layer of powder bed and are found to be in good agreement.