Study On Resistance Heating And Electro Plastic Forming Process Of TC4 Curved Surfaces

Curv surface are widely used in aerospace applications,such as rocket components,aircraft components,aircraft skin and turbine fan blades.Titanium alloys are widely used in the forming of aerospace curved surface because of their high strength,low density,high temperature resistance and corrosion resistance.However,duo to their poor forming performance at room temperature,the resistance-wire heating and die-pressing method is usually used in industry.The biggest drawback of this method is that the low forming efficiency,the high processing cost,and the serious energy waste.In order to solve this problem,a self-resistance heating tension-compression composite forming method is proposed.The electroplastic effect and Joule heat effect of self-resistance heating are used to improve the formability of titanium alloy,improve the forming efficiency and reduce energy loss.The tension-compression composite method is used to improve the stress state of the workpiece and reduce the springback,so as to improve the forming accuracy of the workpiece.In order to explore the forming process and determine the process parameters,the following work has been carried out in this paper:（1）In order to determine the high temperature formability of TC4 titanium alloy under resistance heating,the high temperature tensile test of TC4 titanium alloy under resistance heating was carried out on Gleeble,and the flow stress curves at different temperatures and strain rates were obtained.The results show that the plastic forming index（yield strength,tensile strength and extensibility）of TC4 titanium alloy increases with the increase of temperature and the decrease of strain rate.（2）The thermal deformation parameters of TC4 titanium alloy are solved by high temperature tensile test data,the constitutive equation of hyperbolic sinusoidal function model with Z parameter is established,and the processing map of TC4 titanium alloy is drawn.The optimum deformation conditions(The deformation temperature is about820℃,and the strain rate is 0.01s^-1.)of thermoplastic processing are further clarified,and the criterion of instability and the deformation region of easy instability in hot working are given.（3）Based on Abaqus,thermal-electrical coupling and electrical-thermal-structure coupling numerical simulation were carried out for the resistance heating temperature rise process and the dynamic forming process respectively,and the temperature field and deformation field during the self-resistance heating process of titanium sheet were analyzed,the suitable loading current density is 10A/mm².The springback under different parameters was simulated,and the influence of each parameter on springback was studied.The optimum process plan,heating time were determined,It is concluded that the temperature contributes more to the reduction of springback;the larger the radius of curvature of the titanium plate,the larger the resilience value;the larger the tensile force,the smaller the resilience value;the larger the friction coefficient,the larger resilience value.（4）Design and build the experimental platform of self-resistance heating forming and the bending die of the forming part.Combining with the appropriate technological parameters,the experimental platform is used to verify and analyze the experimental parameters and the finite element numerical simulation.The main purpose is to verify the forming quality and curvature radius on springback under different curvature radius.The test shows that the simulation has a kind of predictability of rebound tendency,and the maximum error between experiment and simulation is 15.8268%.