Research On Deformation Mechanism Of Springback Induced By Cutting Thin Part Optimization Of Fixture

Thin parts tend to be deformed under the clamping force, cutting force, cutting heat and thermo-mechanical effect in machining. The internal re-sidual stress and the as-machined residual deformation deteriorate the final machining precision. In this study, aluminum alloy6061is used to examine the cutting deformation mechanism of thin parts. Specifically, the residual stress and deformation generated during the machining process are studied based on fixture layout and clamping force. The study is meaningful for the control of cutting deformation of thin parts.The surface residual stresses in milling aluminum alloy6061were measured with Doelle-Hauk method. The measurement shows that the prin-cipal plane is approximately parallel with the machined surface of the workpiece, and stresses are under two-dimensional plane stress state. The model was established between milling parameters and surface residual stress by the range analysis and orthogonal experiment method, establish the relationship model by the means of Response surface principle. The parameters were optimized based on overall consideration of surface re-sidual stress and surface roughness. Then the experiment of milling surface of thin parts was conducted under different fixing schemes. Based on the result and analysis of experiment, the thin part with fixing under surface support features a large springback after removing fixture, which heavily affects the precision of thin parts. For fixing of point support, the defor-mation varies as the support points change.To simulate the cutting surface and springback of the parts, a two di- mensional model of was built with Package Abaqus. Deformation and in-ternal stress distribution is studied for different fixing. For surface support, the thin part has a large deformation caused by springback, and the spring back is the main factor of deformation of thin parts. For surface support, the internal stress of thin part along the thickness mainly concentrates on the surface. Meanwhile the stress along feed direction is far greater than the stress along the thickness and shear stress. Therefore, subsequent studies focus on the stress along the feed direction. For point support, under the condition of the position of clamping force and point support on the oppo-site, the springback, deformation and the distribution were severely affected by the position of point support and surface support. Meanwhile the de-formation and internal stress had no direct relation.The deformation mechanism was studied for the springback of thin parts along the thickness. The deformation zone was divided based on the dislo-cation theory. And the springback is analyzed with force between each other for surface support. At last the main reason for springback is the re-distribution of internal stress.The model of relation between cutting stress along the thickness and cutting parameters was established using Response surface principle and Polynomial fitting principle. By comparison of predicted stress and ex-periment stress, the model is robust for predicting cutting stress along the thickness. Basically, the cutting stress is tensile stress on the surface, then quickly decreased to the maximum compressive stress, then slowly in-creased to zero.For the point support, a prediction model was established using BP Neural Network between the deformation, internal stress and the thickness, length, clamping force, the ratio of the position of point support and the length of thin part. The position of point support is important for the de- formation and distribution of internal stress through analysis using the prediction model. Thus, the position is optimized using genetic algorithm, in which the sorting method was designed for guaranteeing the diversity of population and the elitist strategy was used for preserving the lost of ex-cellent individuals in the process of evolution, for the thin part with fixed size based on the minimization of deformation and internal stress.For undercut, the strain superposition principle is used, using which the predeformation and prestress is added to the thin part through optimization of position of clamping force.