Simulation model of laser cleaning based on thermally-induced ablation effects (invited)

In order to study the influence of laser parameters on the performance of laser cleaning based on thermal ablation effects, considering the working mechanism of thermally-induced ablation, Fourier heat conduction equation, and energy conservation theorem, a finite element analysis (FEA) software is used to establish a two-dimensional laser cleaning simulation model of dynamic energy conservation during the thermal ablation. In the simulation model, there is a mathematical relationship between the laser ablation intensity of the thin layer-base system and the normal velocity of the paint layer boundary, by using the virtual Robin boundary condition in the Fourier heat conduction equation. The simulation reflects the dynamic conservation of energy between the laser ablation energy and the latent heat consumption inside paint layers, which confirms the mathematical relationship between the mass loss and the energy consumption, and the simulation results become more precise and reliable. Such a simulation model is used to analyze the effects of the laser power, spot diameter, scanning speed, and scanning energy density on the cleaning performance. The simulation results show that the average residual thickness of a paint layer decreases with the increase of the laser power and scanning energy density, and the decrease tendency gradually slows down. When the laser power becomes too large, the metal base will be damaged. The average residual thickness of the paint layer increases with the spot diameter and scanning speed. However, reducing the spot diameter and scanning speed is harmful to enhance the cleaning efficiency. According to the relationship between the physical parameters of the paint layer and the scanning energy density, the optimization protocol of laser cleaning parameters has been proposed by considering both the cleaning performance and the cleaning efficiency. The simulation model is also used to analyze the cleaning performance of each scanning of an uneven surface paint layer by the uninterrupted multiple scanning. The study in this paper could be helpful for the design of laser cleaning devices as well as the optimization of laser parameters.