Study On Mechanical Properties And Manufacturing Process Of SPF/DB For Pyramid Lattice Structure Of TA15

TA15 titanium alloy is often used to fabricate structural parts with complex shapes and complicated load conditions due to comprehensive mechanical properties,good processability and weldability.Through the reasonable design of its internal space structure,the lattice truss sandwich structure not only has the characteristics of light weight and high strength,but also easy to realize the integrated design of multifunctional,and has a good application prospect.The superplastic forming/diffusion bonding(SPF/DB)technology is introduced to fabricate the lattice truss sandwich structure of TA15 titanium alloy,which has outstanding advantages for solving the difficult problems of difficult formation of titanium alloy at nonnal temperature and complicated shape of lattice structure.The mechanical behavior of the lattice structure after forming under different load conditions is studied,and its use as a structural member has important significance for performance evaluation and guiding design.There are still great gaps in the study of the mechanical properties of TA15 titanium alloy used in the preparation of lattice truss sandwich structure and TA15 titanium alloy lattice truss sandwich structure.In view of the above problems,this thesis based on the existing SPF/DB method of preparing lattice structure,using finite element simulation and experimental research methods,the process parameters of TA15 superplastic degeneration,SPF/DB preparation TA15 pyramid lattice structure,The mechanical properties of the pyramid lattice structure after forming have been systematically studied.The main contents are as follows:(1)This thesis explored the superplastic deformation mechanism of TA15 titanium alloy The superplastic tensile test and the metallographic test of the sample after fracture at different temperatures and strain rates of TA15 titanium alloy were carried out to study the superplastic deformation law and mechanism of the material.The optimal forming temperature and strain rate of superplastic forming of TA15 titanium alloy were obtained,and the Backofen equation of steady-state rheological phase under the optimal forming parameters of the material was obtained,which was used to simulate the formation of lattice truss sandwich structure of TA15 titanium alloy(2)The pyramid lattice truss sandwich structures were fabricated by superplastic forming/diffusion connection.Using the superplastic constitutive model of TA15 to simulate the superplastic forming of the pyramid lattice structure,the forming loading curves of different geometric parameter structures were obtained,and the optimal SPF/DB process path and process parameters were obtained.Under the condition of better process parameters,the lattice truss sandwich structures of TA15 titanium alloy with different geometrical parameters were fabricated by SPF/DB process(3)This thesis studied on the compressive performances of pyramid lattice structure by simulation and experiments.The finite element simulation of the compression performance test of the geometric model of the superplastic forming simulation results retained the characteristics of the superplastic forming process and was more consistent with the actual situation.The effects of core thickness.rib width.cell size and other parameters on the compressive performances of the pyramid lattice structure were investisgated.The lattice truss sandwich structure of the pyramid fabricated in the previous step was cut into a compressed sample for test verification.(4)This thesis studied the performances of the pyramid lattice structure under 3-point bending by simulation and experiments.Firstly,the bending specimens were simulated by the superplastic process,and the parts in the superplastic forming result file were introduced into the bending performance test model,with the superplastic forming process characteristics retained,to study the effect of the panel thickness,core thickness,rib width and unit size on the bending performance of the pyramid lattice structure.The lattice structures of several parameters were taken from all the simulations to verify the reliability of the simulation results.