An SPH Approach to Model the Influence of Assist Gas Forces in Laser Cutting

Abstract Laser cutting is a non-contact thermal-based material removal technique that offers various advantages over conventional machining processes. The workpiece is melted by a high-powered laser beam and the resulting melt is blown away by a jet of gas. The laser assist gas is crucial as it influences the cutting speed, edge quality, and thermal effects, ultimately affecting the overall efficiency and accuracy of the process. However, modeling the laser assist gas is highly challenging due to the immense computational costs associated when dealing with shock waves, turbulence, and high speed jet dynamics. An approach is presented to model the formation of the cutting front and the dynamics of the melt film, influenced by the cutting assist gas forces acting upon it, using the Smoothed Particle Hydrodynamics (SPH) method. SPH is able to deal with large material displacements and moving boundaries occurring in the laser cutting process. The forces applied to the melt film and cutting kerf are modeled using the Continuum Surface Force approach and boundary particle detection. Consequently, the effects of the assist gas are calculated without modelling the assist gas phase domain, saving a significant amount of computational cost and reducing the complexity of the model. The SPH model is coupled with a ray-tracing scheme and a Fresnel absorption model to determine the laser-material interaction. The presented approach is compared against experimental data from literature, showing good agreement with the experimentally observed cutting front formation, melt ejection, phase transition, dross formation, and striation patterns. The results show that SPH can be effectively applied in applications related to laser cutting, showing its potential to design precise and accurate numerical models. Moreover, the proposed parameterized model can help to optimize process parameters to maximize material utilization and reduce energy consumption, operational cost, and processing time during laser cutting.