| Optical aluminum has the advantages of short manufacturing cycle,easy molding,light weight,etc.The combination of a mirror and the support structure made of aluminum alloy can improve the temperature adaptability and stability of the optical system,so aluminum mirrors are more and more widely applied to aerospace,military defense and other important areas.Through the ultra-precision machining of aluminum alloy materials,optical reflectors that meet the imaging requirements of infrared optical systems can be obtained.However,the phenomenon of light scattering on the surface of the mirror seriously reduces its optical performance and even destroys the detection device of the optical system.Therefore,it is an urgent problem to explore the main factors that affect the light scattering characteristics of the mirror surface so that it can suppress or eliminate the surface scattering phenomenon.In this thesis,considering the effects of various factors such as machining kinematics,tool geometry,machining parameters,plastic flow measurement,elastic recovery,and processing vibration on the surface topography,an ultra-precision turning surface three-dimensional topography model is established based on MATLAB software.Simulation analysis of the influence of vibration frequency on the number and shape of ridge peaks during turning.On this basis,a three-dimensional topography model of fly-cutting and grinding machining under given roughness was established.The above-mentioned topography model will be introduced into the subsequent electromagnetic field simulation and used as part of the geometric model.In order to quantitatively describe the light scattering characteristics of the machined surface,a bidirectional reflectance distribution function(BRDF)was selected as the research carrier,and a correlation formula between the BRDF and the electric field intensity was deduced using related theory.The simulation model of electromagnetic field was established based on COMSOL finite element simulation software.The incident light source was set in the form of the background field plane wave,and BRDF distribution curve was obtained by MATLAB processing.Change the simulation parameters and explore the differences between the three types of surface scattering characteristics of turning,flying and grinding,and verify the superiority of the turning processing method.On this basis,the effects of feed amount,vibration amplitude,radius of the arc of the tip,and the wavelength of the incident light on the surface scattering characteristics during the turning process were analyzed,and the corresponding mechanism of various factors was analyzed.The ultra-precision turning machining experiment of Al6061 was carried out.The surface morphology and roughness of the workpiece were detected by using a laser interferometer and a white light interferometer.The correctness of the profiling model was compared with the simulation results.The BRDF detection system was used to detect the scattering performance of the workpiece surface,and the influence of the turning feed amount and the incident light source angle on the distribution curve of BRDF was analyzed.According to the corresponding parameters of the samples used in the experiment,the modeling and simulation were performed,and the results were compared with the experimental results and error analysis was performed to verify the accuracy of the previous electromagnetic field simulation results. |
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