Improving FEM-based solid mechanics simulations for ultrashort pulse laser ablation by integrating an equation of state and material separation

• Development of a two-temperature solid mechanics model incorporating an equation of state. • Inclusion of a spallation mechanism for material separation in the FEM approach. • Efficient and accessible implementation using COMSOL Multiphysics. • Verification against experimentally validated hydrodynamic simulations. • Improved accuracy over classical isobaric solid mechanics models. Accurate simulations are paramount for deepening our understanding of ultrashort pulse laser ablation, a complex process involving non-equilibrium thermal and material transport on time-scales spanning several orders of magnitude. In response to this need, we propose a novel approach that enhances the use of a readily available finite element method tool for multiphysics simulations by incorporating an equation of state (EOS). This new model, termed the two-temperature solid mechanics model including EOS (SM-EOS), has been meticulously tested against isostatic changes and compared with an experimentally validated two-temperature hydrodynamic simulation (HD). Further comparison was made with classical TTM solid mechanics (SM-ISO) simulations using constant or isobaric material parameters. A mechanism for describing material separation due to spallation is also incorporated in the model. Bulk aluminum serves as prototype within this investigation. Our results show that SM-EOS aligns closely with HD, significantly outperforming the classical SM-ISO simulations. Given its robust performance and ease of implementation, our SM-EOS model is expected to serve as a valuable tool for both research groups and industrial applications, thereby facilitating further investigations into ultrashort pulse laser ablation phenomena. Furthermore, it is expected that our approach could influence other fields in simulating phase transitions and extreme states of matter utilizing solid mechanics calculations.