Numerical Simulation And Experimental Research On Nano-second Pulse Laser Paint Removal

Surface cleaning technology is widely used in the repair / remanufacturing of mechanical parts,and it is the prerequisite for the repair,testing and assembly of damaged and obsolete parts.Aiming at the disadvantages of the traditional cleaning technology that damage the substrate and pollute the environment,this topic takes a typical automotive engine block material,HT250 gray cast iron,as the cleaning object,and a research method combining theoretical analysis,numerical simulation and experimental research were used in order to study the paint removal mechanism and process control method of nanosecond laser cleaning process,which provides theoretical support and process data for the application of nanosecond laser cleaning process in the field of mechanical repair / remanufacturing.The main research contents are as follows:(1)The bonding characteristics between the paint layer(water-based antirust paint)and the substrate(HT250 gray cast iron)and the interaction mechanism of nanosecond pulse laser and substance was investigated;the model of adhesion between the paint layer and the substrate and laser-induced heat stress model was established;the heat conduction process under the action of laser was studied.the temperature field during laser paint removal was calculated,the temperature distribution of the paint surface and depth direction was analyzed,and the removal process of the paint layer was revealed under the combined action of temperature field and thermal stress;(2)Using ANSYS finite element analysis software,a finite element model of nanosecond pulse laser paint removal was established.The temperature field distribution under the action of a pulsed Gaussian heat source was simulated,and the change law of the temperature field of the paint layer under different laser parameters was studied.The "life and death unit technology" was used to obtain the surface cleaning morphology of the substrate and paint layer after laser paint removal,and studied the process of removing the paint layer and the process of generating pits or grooves on the surface of the substrate,and analyzed the thermal stress distribution and morphology under the action of heat and force of the substrate and paint layer,which provides basis for analysis of paint removal mechanism and optimization of process parameters;(3)Nano-second pulse laser paint removal experiments was carried out.By fitting the relationship between laser energy density with laser ablation area and depth,the initial cleaning threshold,substrate exposure threshold,full cleaning threshold and substrate damage threshold during laser paint removal are measured.The surface morphology of the residual paint layer after laser paint removal was analyzed,and the evolution mechanism of ablation gasification and vibration separation of the paint layer under laser-induced heat / force was revealed;(4)The removal effect of the paint layer under different laser parameters(laser power,laser frequency,scanning speed,etc.)was evaluated,including the surface micro-morphology,surface roughness,surface element distribution of the substrate and paint removal rate.After comprehensively considering the surface quality and cleaning efficiency after paint removal,the laser parameters were optimized and analyzed,which laid the foundation for the application of laser paint removal technology.