Experimental Study Of Titanium Alloy Sheet Incremental Forming

Incremental sheet forming(ISF),featuring large flexibility and elimination of tailored dies,is extremely suitable for the manufacturing of small-batch production,customized sheet metal parts in fields such as aerospace,medical rehabilitation and etc.Currently,titanium alloys are widely used in aforementioned areas.Hence,there has actual application value in ISF experimental study of such materials(TC4,TA1).As for TC4 material,electricity-assisted ISF was adopted to improve its poor formability at room temperature.In the meanwhile,attention was focused on the rough surface quality of the formed part and severe abrasion on tool tip;And for TA1 material,single-pointed ISF was selected to investigate the correlation between microstructure and formability.Furthermore,double-sided ISF was used to explore its effect on the forming quality of the cranial reconstruction.The main experimental results are as following:1)Four novel forming tools were designed for the high temperature electricity-assisted ISF of TC4,namely solid tool,inner water cooling tool,rolling-ball tool and rolling-wheel tool.Compared with conventional forming tools,major changes concern tool material and structure,including the selection of GH4169 nickel-based superalloy and the design of water cooling and rolling tip.Experimental results indicate that when integrating the three mentioned elements into one forming tool,the surface quality of the formed part can be greatly improved as well as that of the tool tip.In contrast with solid tool,surface roughness of the part formed by rolling-ball tool can be reduced up to 72.6%.2)Temperature evolution trend was explored during the E-ISF process of TC4,including temperature data of the global sheet blank,a certain point on the blank and tool tip.The variation ranges of control circuit used for different forming tools were obtained so that excessive oxidation of the formed part can be avoided throughout the process.3)Correlation between initial grain size and TA1 formability was investigated.When the grain size decreases from 234?m to 24?m,the maximum forming angle increases 10.9°.Observation reveals that twinning is the main deformation mode during the ISF process.4)Double-sided ISF with local support and peripheral support forming strategy were compared during the TA1 cranial reconstruction.Experiments show that the latter strategy can not only relieve the maximum thickness reduction up to 10%,but also improve the surface quality.