Transient numerical simulation of CO_2 laser fusion cutting of metal sheets: Simulation model and process dynamics

摘要

Simulations are a versatile tool of increasing importance for profound analysis and comprehensive understanding of laser-based material processing. Based on our simulation model of laser-matter interaction, we developed a numerical three-dimensional model for the transient simulation of fusion cutting of sheet metal. This model is based on the finite-volume method (FVM) and covers various laser-metal interaction mechanisms, such as multiple surface reflection and absorption according to Fresnel, but also more complex interactions like absorption in the metal plasma. In this study, we focused on a Gaussian shaped CO_2 laser beam applied for the cutting and steel sheets. The implemented physics include fluid and vapor dynamics according to Navier-Stokes, heat conduction, the surface tension of the liquid-vapor interface and the modeling of the enthalpies of fusion and vaporization. As accurate input parameters are crucial for any simulation, special focus was put on the implementation of material properties at temperatures around the melting point. The additional modeling of inert process gas ensures realistic blow-out of the molten material. Furthermore, adaptive meshing enables high calculation accuracy in the areas of interest while minimizing computation time drastically.