Research On Formability Control And Optimization And Coupling Simulation On Friction Stirring Assisted Incremental Sheet Forming For Aluminum Alloy

Incremental sheet forming(ISF)is a novel flexible forming technology without mold,which is suitable for small batch or customized sheet metal forming.In order to meet the requirements of forming difficult-to-form materials,improving the formability of sheet metal has become a research hotspot.Friction stir assisted incremental sheet forming(FS-ISF)can effectively improve the local temperature and the formability of the sheet.However,it is difficult to control the formability and surface quality.With the support of National Natural Science Foundation of China(Grant#U1737210)and Program of Shanghai Academic Research Leadership(Grant#19XD1401900),the effects of process parameters on the forming temperature and the surface quality in FS-ISF were analyzed;Through orthogonal analysis,the formability of the sheet was improved with well surface quality,and the recommended process windows were calibrated;In order to predict the forming temperature and stress-strain field in FS-ISF,an effective thermo-mechanical coupling simulation method was established.And with a novel acceleration method,the efficiency of the simulation was improved.The key conclusions are summarized as follows:The effects of rotating speed,step down,feed speed,and tool geometry on forming temperature and surface quality in FS-ISF were systematically studied by orthogonal analysis.The effect of rotating speed was greatest,followed step down.The flat tool could increase the forming temperature.But the feed speed won't affect the temperature.Cutting and fish scales were the surface defects in FS-ISF.A reasonable combination of rotating speed and step down could avoid cutting;To avoid fish scale,the ratio of feed speed to rotating speed should be greater than2 mm.A process window for FS-ISF was proposed,combined with forming temperature and surface quality.The applicability of process window proposed was verified by forming experiments on two aluminum alloys(AA2024-T3 and AA5052-H32).The rotating speed as 4500?6000 RPM,step depth as 0.15?0.3mm and feed rate as 1500?2000 mm/min with the flat tool were the optimum process parameters,among which the reasonable temperature ranges of optimal area were 170?200? for AA2024-T3,and135?150? for AA5052-H32,respectively.For the simulation of FS-ISF,an efficient thermal-mechanical coupled simulation method was developed,basing on two acceleration method:compressed equivalent tool and scaling of thermal conductivity of sheet metal.The former could significantly improve efficiency by 226%,and together with the latter,efficiency could be further improved by 316%.The research in this thesis provided an effective method for improving the formability and keeping good surface quality in FS-ISF,and gave a reference for the thermo-mechanical coupling simulation for the similar process.