Research On The Laser Ablation Properties Of Ultra-precision Cutting Aluminum Alloy

With the development of related technologies,the laser fluxes experienced by optical components in high-energy laser system have surged.To make sure that the optical components in the system is reliable,we need more stricter requirements in the cleanliness of the system.However,contaminants always generate when stray light in the system irradiates mechanical components.This can reduce the cleanliness of the system.Moreover,in the clean control link of the system,there is a lack of clean control at the machining stage of mechanical components using traditional machining methods.Therefore,studying the influence of the machining stage of mechanical components on the clean environment of the high-energy laser system and analyzing the ability and conditions to achieve ultra-clean manufacturing of mechanical components are very important.The research results of all can play a necessary role in the reasonable selection of machining parameters of the mechanical components in the high-energy laser system.Firstly,the ultra-precision cutting simulation of aluminum alloy was carried out using molecular dynamics theory.The effects of cutting parameters on cutting force,cutting heat,residual stress and cutting plastic deformation are analyzed.By calculating the temperature,density and stress of each atom in the subsurface layer,the influence of cutting parameters on the temperature,density,stress change rate and final performance of the subsurface layer was studied.It is believed that changes in the lattice structure will not only cause changes in the stress of the subsurface layer,but also cause changes in the density of the subsur face layer.Secondly,using the molecular dynamics theory based on the dual-temperature model,the laser ablation model was established by using aluminum alloy machining parts obtained by ultra-precision cutting simulation as the substrate.By extracting the peak of the kinetic energy of the substrate in the depth direction and the negative peak of the atomic movement of the substrate in the depth direction,the influence of the subsurface layer of the machining part on the energy transmission rate of the laser and the speed of the stress wave is analyzed.It is believed that the plastic deformation ratio of the substrate will affect the laser energy t ransmission rate,the excited atoms in the substrate will hinder the propagation of stress waves.The cluster analysis algorithm and three-dimensional convex hull fitting were used to analyze the contaminants produced by aluminum alloy machining parts.The influence of cutting parameters on the quantity and volume of particulate contaminants produced by aluminum alloy machining parts is revealed.By stratifying the substrate loaded with local laser in the depth direction,the source of the particulate contaminants was studied,and it was believed that most of the contaminants came from the area irradiated by the laser.Thirdly,The Weierstrass-Mandelbrot fractal function was used to simulate the machined surface.Then the aluminum alloy substrates with different roughnesses were prepared by molecular dynamics simulation,and a laser ablation model was established with these substrates.The effect of substrate surface roughness on laser energy transmission and stress wave transmission is analyzed.It is believ ed that the roughness has no effect on the energy transmission rate and stress wave velocity of the laser.Through the analysis of cluster contaminants,it is believed that the roughness will affect the amount,angle and volume of the contaminants finally produced by the aluminum alloy substrate.The linear relationship between the volume of the ablation pit and the roughness of the substrate was revealed by extracting the volume of the ablation pit produced by the aluminum alloy substrate with a rough surface loaded with a local laser.Finally,the adsorption model between the high-speed pollutants sputtered by laser ablation and the aluminum alloy substrate with rough surface was established.The adsorption behavior of particulate contaminants with high velocity and planar contaminants with high temperature and high velocity on rough aluminum alloy surfaces were analyzed respectively.And the effect of roughness on the adsorption energy between the contaminants and the substrate is also studied.