Efficient thermal simulation of large-scale metal additive manufacturing using hot element addition

Directed energy deposition processes can reduce material waste and manufacturing time of large metal parts through near net-shape production at high deposition rates. However, the localised high heat input gives rise to undesired heat accumulation, residual stresses and distortions. In this work, a fast thermal model is developed to aid in predicting and preventing these drawbacks by providing insight in the relation between process settings, deposition strategy and thermal response. Material addition and heat input are efficiently combined by adding new elements at elevated temperature. Newly deposited elements are assigned an artificially enhanced heat capacity to match the process heat input. The discontinuous Galerkin finite element method is used for spatial discretisation. The resulting numerical scheme is fully explicit and can be solved element-wise. Unlike previous prescribed-temperature heat input models, the proposed method correctly captures the process heat input, irrespective of substrate temperature and element size and without calibration. Comparison with experimental data shows that the thermal history of a large additively manufactured part can be accurately predicted.