Preparation And Mechanical Properties Analysis Of Pyramid Lattice Structure Based On Vacuum Electron Beam Welding

Pyramid lattice structure is composed of a certain arrangement of bars and the upper and lower panels.lt has the advantages of light weight,high specific strength and high specific stiffnes and applied to aviation,automobile,submarine and other fields.In this thesis,5083 aluminum alloy and TC4 titanium alloy pyramid lattice core were formed based on the joint compression method.The parameters of vacuum electron beam welding were optimized by response surface method.A pyramidal lattice structure of aluminum alloy and titanium alloy was fabricated by vacuum electron beam welding.The dynamic and static mechanical properties were studied by experiments and numerical simulations.The main research contents and results are as follows:(1)Study on the preparation technology of 5083 aluminum alloy pyramid lattice structure.A 5083 aluminum alloy pyramid lattice core was formed based on the node compression method.The vacuum electron beam welding parameters were designed and optimized by the response surface method.Based on optimized welding parameters,special welding tooling was designed,and the panel and core were connected by vacuum electron beam welding,and the lattice structure was prepared.(2)Experiments of flat compression,bending,shear and Hopkinson impact on the lattice structure of aluminum alloy were carried out.The load-bearing,deformation and failure modes of the lattice structure under different static loads were obtained,and the load-bearing and energy-absorbing characteristics of the lattice structure under high-speed impact were studied.The results show that the failure mechanism of flat pressure is mainly reinforcement buckling,the failure mode of bending is mainly panel buckling and reinforcement buckling,and the failure mode of shear is the separation of core solder joint and the fracture of reinforcement.The lattice structure has excellent energy absorption and specific energy absorption under high speed impact.(3)The aluminum alloy core forming and lattice structure flat pressure,three point bending,shear and large diameter Hopkinson impact simulation were carried out.The forming simulation of 5083 aluminum alloy core was carried out based on Abaqus,and the obtained core simulation size is in good agreement with the experimental size.Based on the core model after forming simulation,the simulation of flat pressing,three-point bending,shear and large diameter Hopkinson impact was carried out.The mechanical properties and deformation of lattice structures under static and dynamic loads are studied.Compared with the experimental results,the reliability of the simulation model is verified,which provides guidance for the subsequent research on the mechanical properties of pyramid lattice structures of different sizes.(4)Preparation technology and flat compression properties of TC4 titanium alloy Pyramid lattice structure.The forming of TC4 core was studied by using Formkote T-50 antioxidation lubricant.The oxidation resistance of the lubricant was verified by microhardness and EDS line analysis,and the core was prepared at 650℃.The TC4 vacuum electron beam welding parameters were optimized by response surface method,and the connection between the panel and the core was realized,and the pyramid lattice structure was prepared.The flattening deformation rule,flattening strength and flattening modulus of titanium alloy lattice structure were obtained.The main failure mode of the pyramid lattice is the fracture of the bar,and the solder joints are not unglued in the whole process of flat pressing.