Experimental Study On Single Point Incremental Forming Of TC4 Titanium Alloy Sheet Based On Temperature Control By Resistance Heating

Titanium alloys possess high specific strength,excellent biocompatibility and corrosion resistance,thus it's widely used in the aerospace,energy chemical and medical fields.On account of its poor plasticity at room temperature,hot forming is most frequently used for the titanium alloy sheet deformation.The electrothermal assisted incremental forming technology is an advanced hot forming technology,which is suitable for single piece or small batch titanium plate parts.With the technical advantages of electrothermal forming and local loading forming,it can improve the forming ability of titanium alloy sheet effectively.However,electrothermal assisted incremental forming is a complex dynamic deformation coupled with multiple physical fields.Under the temperature continuously rising with electric heating effect,the microstructure of Titanium alloy sheet became heterogeneous,and made the quality of material forming extremely challenging to control.Hence,in order to achieve the forming temperature control,an incremental forming resistance thermal temperature control system was designed in this thesis.And the main research contents of this article are as follows:Based on the groove model,the single point incremental forming performance of the TC4 titanium alloy sheet based on temperature control by resistance heating of the common tool head was carried out.Based on the DIC system,the strain fields of the specimen during the forming process were obtained.The forming force and fracture characters at different temperatures were explained.By investigating the effect of forming temperature on forming performance of TC4 titanium alloy,the microscopic explanation of forming performance improvement at different temperatures were given.In order to protect the insulation parts of tool shank,a water-cooled tool head was designed.And the single point incremental forming tests with water-cooled tool head and temperature control by electrical heating were carried out.From the macro and micro view,the changing rule of the forming performance,forming force and springback of the parts at higher forming temperature(room temperature-600?)was studied.Based on the variable angle truncated cone model,the single point incremental forming process of the TC4 titanium alloy sheet for water-cooled tool head with temperature controlled was developed.The effect of temperature on the forming performance and forming limit angle were discussed.The changing rule of hardness,surface quality and microstructure at different material directions under the thermal resistance temperature control process were described.In addition,the evolution of the specimen microstructure during the forming process was analyzed.And the effect of anisotropy on microstructure and mechanical properties were described.Based on the variable angle cone model,the single point incremental forming performance experiments with constant current heating and temperature control heating were carried out with water cooled tool.And the forming performances under the two processes were compared.Based on the constant angle cone model,the difference between the temperature of the sheet and the tool head under the two processes was studied.The changing rule of hardness and surface quality of the parts under the two processes were analyzed.The changing rule of forming force and microstructure under the two forming processes were described.