Research On Ultra-precision Turning Processing Aluminum Alloy’s Surface Mechanical Properties And Process Optimization

Ultra-precision machining is an important technique in the field of mechanicalmanufacturing, which greatly impacts the development of cutting edge technique andnational defense industry. The main goal of ultra-precision machining is to obtain highform precision and high surface quality (including small surface roughness and goodmechanical properties) for work pieces, which are related with machine tool, processing,cutting tool, environment conditions, and other factors. As one of the most commonlyused material, aluminum alloy has good electrical, mechanical, chemical, and thermalproperties as well as decent performance inneutron engineering, and anti-irradiationinjury. The aluminum alloy target parts in the laser fusion system are required to bemachined with high surface precision and good surface mechanical properties.Therefore, research on the surface mechanical quality of ultra-precision turnedaluminum alloy has very good practical significance and application prospect.With the aim of obtaining high quality surface, research was conducted on theoptimizing of aluminum alloy processing parameters of ultra-precision turning.First of all, according to Johnson-Cook material constitutive equation,3D FEMmodel of ultra-precision turning aluminum alloy was built based on thermomechanicalcoupling; the processed surface by cutting several times was simulated; the simulationresult data of FEM model was then analyzed to unveil the underlying change rules ofworkpiece surface residual mechanical stress when cutting depth, feeding rate andcutting speed were changed.Secondly, the processing of ultra-precision turning was planned. To eliminate theinfluence imposed by the previous machining procedure, all the workpieces wereannealed by heat treatment first. Then the end face of aluminum alloy specimen wasturned to mirror-like surface. The residual stress of machined surface was thenmeasured, the result of which was used to validate the FEM model. Moreover, themicro-hardness of the machined surface was also measured to investigateconsequences of aluminium alloy work hardening.Finally, FEM simulation scheme was planned based on the results of general rotarytest. The regression equation of residual stress was obtained; Work hardening degreemodel based on BP neural network was built; The mathematical model of residual stressand work hardening was then took as constraint condition. Processing efficiency wasinitially set as the optimization goal, and hybrid genetic algorithm was used to optimize processing parameters of ultra-precision turning--the parameters should be able to meetthe requirements of high quality machined surface and to improve the efficiency of themachining as much as possible.