Numerical Simulation of Chemical Reaction Mechanism during Ultrafast Laser Ablation with Different Pulse Numbers under the Action of Plasma

In order to reduce the experimental cost of laser processing and establish a relatively perfect laser processing simulation model to predict the ideal oxide distribution on the surface of the material, a three-dimensional thermochemical reaction model based on computational fluid dynamics equation, fluid-structure coupling theory and two-temperature model of ultrafast laser ablation is investigated by means of C++ self programming with the help of fluid simulation platform OpenFOAM. In the model, the absorption and defocusing effects of plasma on incident laser energy are considered, and the effects of temperature change on surface reflectivity and layered absorption coefficient are analyzed. The diffusion phenomenon among multicomponent components is simulated by Maxwell Stefan theory, and the thermochemical reaction rate is fitted by partition function method. The experiments of laser drilling with 240 fs pulse laser at the same power and different pulse numbers are carried out to verify the effectiveness of the simulation model. The experimental results show that the diameter of the microporous structure on the surface of the ablated material, the shielding effect of the plasma on the laser and the oxide content in the ablated region gradually rise up with the increase of the number of pulses. By comparing the simulation results with the experimental results, it can be seen that the relative error is less than 5% in simulating the diameter of the surface microporous structure, and within 12% in simulating the surface oxide content. It is analyzed that when the pulse number is smaller, the plasma effect is weaker, and the thermal effect accounts for a larger proportion, which makes the larger error of the oxide proportion between the simulation and the experiment. In this paper, plasma and chemical reaction module are combined to solve the thermochemical reaction rate by partition function method. The content of oxide on the surface of materials can be predicted. © 2024 Chinese Mechanical Engineering Society. All rights reserved.