High-efficiency Superplastic Forming Technology Based On M Value Theory For TA15 Aircraft Bulkheads

TA15 alloy is one kind of near- ? type titanium alloy with not only good weldability of ? type titanium alloy, but also processing plasticity of ? ?? type titanium alloy, so the comprehensive performance is excellent. It has been widely used in aerospace aviation to manufacture aircraft bulkheads, landing gear and other components.Forming bulkheads is difficult because the stiffener of parts is high and the sidewall is thin. How to make the forging forming easy, high efficient, and reduce the load is an urgent problem. Based on the value of m deformation, an efficient superplastic forming method is proposed to investigate the whole forming process of TA15 alloy aircraft bulkheads and analyze optimal parameters by using the finite element simulation software Deform. Possible defects during forming are also explored.Based on data of tensile test, the superplastic constitutive equation of TA15 titanium alloy is studied. At the temperature of 850℃-950℃, thermal activation energy 216.7kJ/mol is calculated and the constitutive equation is built based on Arrhenius constitutive equation of the classic hyperbolic sine function. The error of constitutive equations is found by testing, the precision of constitutive equations reaches 99.3 percent after using 1stopt software to correct, it shows the relationship between the thermodynamic parameters of material and flow stress better. It shows a great agreenment between the simulated and experimental results, which proves the corrected constitutive equations are more real based on the simulation and verification of constitutive equation by using software Deform-3D.On the basis of parts diagram of bulkheads, software UG is used to design cold forging and hot forging drawing after check out relevant information and consider the shape and size of flash gutter, then design and draw slot of forging model. The software Deform-3D is used to optimize initial blank when the blank of bulkheads part is designed, the defects of filling dissatisfaction and volumetric uneven distribution have been improved through analysis of the simulation results, then determine optimal blank. Forgings map, forging die chart and optimal blank for bulkheads of shrink ratio is designed by use the method of model design, which provides a theoretical model for three-dimensional numerical simulation.The proposed constitutive equation of TA15 titanium alloy is regarded as the material model, and the optimum temperature 900 ℃determined experimentally is treated as forming temperature. Forging process of original bulkheads is simulated after importing them to software Deform-3D wnere the original map of bulkheads die and blank is regarded as three-dimensional models. The result shows that compare to the forging load 9051 t of superplastic forming, 19708 t of isothermal forging and 33001 t of conventional forging shaping, forming load of original bulkheads is only 7233 t by using the method of efficient superplastic forming, the equivalent stress and equivalent strain is small, forming effect is good. Also, the shaping time of efficient superplastic forming is shorter than superplastic forming, efficiency improves nearly doubled. The method of efficient superplastic forming is used in the numerical simulation on bulkheads of reduced scale, the forming load is 385 t, providing theoretical support for the practical forming of scaled bulkheads forgings in the 400 t hydraulic press.