Research On The Cleaning Mechanism Of Nanosecond Pulse Laser Cleaning The Pollution Oil On Steel Plate Surface

In industrial production and manufacturing,with the long-term service of mechanical equipment,dirty oil will appear on the surface of mechanical equipment and its internal parts.Regular industrial cleaning of mechanical equipment is an important guarantee to ensure the normal transportation of equipment and extend the service life of the equipment.In recent years,With the development concept of low carbon,energy saving and emission reduction advocated.In view of the shortcomings of traditional degreasing methods such as low efficiency,easy damage to parts,and environmental pollution,there is an urgent need for a new degreasing technology with high efficiency,controllable cleaning degree,environmental friendliness,and easy operation.As a non-contact,"green"cleaning process,laser cleaning and degreasing are expected to partially or completely replace traditional cleaning and become the green cleaning technology with the most development potential.Therefore,it is of great significance to carry out research on the nanosecond pulse laser cleaning mechanism of dirty oil on the steel plate surface and provide the theoretical and technical basis for the large-scale application of green laser cleaning of dirty oil on the steel plate surface.The main work content of this paper is as follows:（1）Study the propagation characteristics of laser in dirty oil layer（multifunctional grease）and steel（Q235B）substrate and the bonding characteristics of dirty oil and steel substrate.It is obtained that the absorption coefficient of the dirty oil used in this experiment is about 1.022×10^-4mm^-1when the laser wavelength is 1064 nm,the optical penetration depth is about 10 mm,and the adhesion between the dirty oil and the steel substrate is about 1.196×10⁸N/m².Based on heat transfer and solid mechanics,the heat conduction model and thermal stress model of laser cleaning and degreasing are established.（2）Using COMSOL Multiphysics to simulate the temperature field and thermal stress field of nanosecond pulse laser cleaning the dirty oil on the steel plate surface,the influence of different laser parameters on the temperature field and stress field distribution and change of the oil-base interface was analyzed.The research shows that the peak temperature of the temperature field decreases gradually with the increase of the pulse width and repetition frequency,and the peak temperature and thermal equilibrium temperature of the temperature field gradually increase with the increase of the spot overlap rate and the number of scans,and the change distribution of the thermal stress field the trend is positively correlated with the change distribution trend of the temperature field.（3）Built a nanosecond pulse laser cleaning and laser-induced breakdown spectroscopy（LIBS）spectrum online monitoring device for dirty oil on the steel plate surface,established a spectral detection method for the dirty oil on the steel plate surface based on LIBS technology,and obtained the characteristic parameters and cleaning effect of laser cleaning mapping relationship.Analyzing the cleaning mechanism of nanosecond pulse laser cleaning the dirty oil on the surface of the steel plate with different laser cleaning parameters,it is concluded that blasting,vibration and ablation mechanisms exist simultaneously in the process of laser cleaning and degreasing,when the laser parameter is short pulse width and high repetition frequency,the dominant mechanism of laser cleaning is blasting and vibration mechanism;when the laser parameter is long pulse width and low repetition frequency,the dominant mechanism of laser cleaning is vibration and ablation mechanism,and the suitable spot overlap The rate and number of scans can effectively reduce the impact of the ablation mechanism on the substrate.