Coupled thermo-mechanical process simulation method for selective laser melting considering phase transformation steels

Selective Laser Melting (SLM) is a promising additive manufacturing technology for the production of complex and highly individual parts on short lead time request. Key aspects for the competitiveness of the SLM process are stability and reproducibility. Poorly optimized pre-processing may lead to deviations in structural properties and geometrical accuracy which results in cost and time consuming iterations. Pre-processing assisted by numerical simulations can reduce defects which occur during construction and hence increase the quality of the parts and the efficiency of this technology. This research work aims to describe a method for a non-linear macroscale finite element method simulation (FEM) to predict a detailed temperature history of the material as well as residual stresses and distortions for medium-sized parts. An advanced calculation procedure is introduced to reduce the calculation effort significantly. It offers an alternative for experimental calibration of faster linear simulation methods (Keller and Ploshikhin, 2016). Specimens have been fabricated via SLM and subjected to distortion measurements for the validation of the developed simulation technique. One austenitic and two martensitic stainless steels are included in the investigated materials. Numerical simulations with consideration of the material specific phase transformations properties have been performed, which show a good agreement with experimental measurements. Significant influence of phase transformations for the residual stresses and distortions is observed.