Research On Quality Characteristics And Multi-objective Optimization Of Laser Cleaning Process

With the continuous development of industry,the remanufacturing technology of auto parts conforms to the trend of energy saving,emission reduction and environmental protection economy,and implements the concept of green and sustainable development.As one of the remanufacturing technologies for surface repair,laser cleaning technology has the characteristics of non-contact,high efficiency and controllability,and environmental protection.It is widely used in the removal of pollution layers and can effectively clean the black glue-like carbon deposits in the engine.In this paper,the quality characteristics of the carbon black layer on the surface of the 6061 aluminum alloy by laser cleaning are used as the main research object,and the mapping relationship between the process parameters and the surface quality is established by the response surface method.The laws of laser cleaning parameters on surface roughness and carbon removal rate are studied.A multi-objective optimization model is established through the combination of response surface method and genetic algorithm.Firstly,based on the principle of laser cleaning the surface contaminants on the substrate,a two-layer three-dimensional thermal stress model for laser cleaning of the carbon black layer on the surface of 6061 aluminum alloy is established by Comsol finite element software.According to the theory of heat conduction and structural mechanics,the temperature field and stress field of the aluminum alloy surface are obtained.The characteristics of the surface of the laser-acting material and the influence of the cleaning parameters on the temperature field and stress field in the laser cleaning process are analyzed.Secondly,the experimental equipment is determined and the response surface test of laser cleaning the carbon black layer on the aluminum alloy surface is designed.The surface roughness and carbon removal rate are used to characterize the surface quality of the aluminum alloy after cleaning.And through the data measured by laser confocal microscope and spectrometer,the mathematical model of the second-order polynomial of the surface quality and cleaning parameters under the response surface test is obtained.The significant influencing factors of surface roughness and carbon removal rate under the results of analysis of variance are analyzed.Among them,the influence of single factors and interaction factors on surface quality is analyzed based on variance data.The most significant single factor of process parameters on surface roughness is modulation parameter pulse width.The order of significant interaction factors is: laser power and pulse width AD> Laser power and scanning speed AC.The order of process parameters affecting the single significant item of carbon element removal rate is: pulse width>scanning linewidth>laser power>scanning speed.The significant interaction factors are: the combination of laser power and scanning speed AC,he combination of scanning linewidth and scanning speed BC,the combination of laser power and pulse width AD.Finally,based on the above response surface method,a mathematical model of laser cleaning parameters and surface quality is obtained to verify the accuracy of the model.Under this premise,the objective function of the multi-objective optimization of surface quality under the model is established,and the Pareto optimal solution set is obtained based on the combined method of response surface-NSGAⅡ,which provides parameter selection for different cleaning engineering needs.Compared with the optimization results of the Design Expert 8.0.6 software,the performance is better.Finally,the surface quality under the best process is verified through experiments,and the absolute error is controlled within 2%,so the optimization model is suitable for the multi-objective optimization of the laser cleaning process.