Mechanics insights into particle ejection during laser cutting of metal alloys

Understanding the mechanism of the particle formation and ejection during laser cutting of metal alloys is crucial. It can not only ensure workpiece’s surface quality but also reduce the formation of micro-particles, a typical hazard to the operators. However, the existing studies rely on experiments, lacking reliable numerical models that can effectively reveal the flow behavior of molten metal at the cutting kerf and the metallic particle formation. Therefore, we presented a numerical model that can simulate the formation and deposition of metallic particles under different processing conditions. This model can help the user better understand the interaction between processing parameters and particle formation, and therefore minimizing the need of experiments during process optimization. An incompressible Newtonian laminar non-isothermal multiphase fluid flow was modelled for the laser-metal interaction process by implementing the Volume of Fluid (VOF) method. The dynamic mesh strategy was employed to capture the metal-gas interface and resolve the free surface of the ejected particles. The formation of particles at the kerf front was illustrated through the temperature/morphology evolution history. The particle shape, size, and velocity distribution over time were revealed by using the Volume of Fluid-to-Discrete Phase Model (VOF-to-DPM) technique. The impact of laser power and the assist gas speed were assessed where the laser power from 500 to 1500 W and assist gas speed from 20 to 60 m/s were chosen, demonstrating that our numerical model offered an in-depth understanding of the mechanics at the kerf regions and assisting the development of subsequent exhaustion systems for secondary emissions.