Multi-objective Structural Optimization Design Of Ti6Al4V Lattice Structure By SLM

With the selective laser melting technology growing more mature and commercial competitive.Body Centered Cubic lattice structure and its enhanced unit have the characteristic of simple topology structure and isotropy,also fits the molding process of SLM,consequently,it attracts many attention.However,body centered cubic lattice structure and its enhanced unit cannot meet both demands of lightweight and high strength.As a result,deciding to use SLM,choosing Ti6Al4 V as the raw material,to set up BCT lattice structure general model,conduct multi-objective optimization research towards lattice structure using theoretical research,finite element analysis and experiment,in order to seek for the lattice configuration which meets both the lightweight and high strength demands.Firstly,the restrictions on the dimensions in all directions of BCC unit cell are lifted,to establish the general model of BCT unit cell and make static analysis.In the process of deducing the mechanical response of BCT lattice under uniform load,the mapping relation between the force and displacement of lattice structure is obtained by solving the stiffness matrix and energy analysis.Secondly,a multi-objective optimization mathematical model of BCT lattice structure size is established by taking BCT unit cell dimensions as the design variables,taking the relative density,initial stiffness and plastic failure strength as multi-objective evaluation functions,taking the lattice size and fabrication process as constraint conditions.And the optimal configuration size of the BCT unit cell is obtained by the ideal point method.Thirdly,The optimized BCT lattices and BCC reference structures are simulated by theoretical simulation and finite element simulation.The Ti6Al4 V experimental specimens of BCT and BCC reference structure are fabricated by SLM.The quasi-static and uniaxial compression tests are also carried out.The theoretical analysis results are confirmed by comparing and analysing the theoretical simulations,the finite element simulations and the experimental results.Example analysis shows that comparing to BCC reference structure,the relative density of BCT optimized structure increase only by 3.7%,but the elastic modulus and yield strength increase by 121.5% and 77.3%,which means the mechanical properties are improved remarkablely.Finally,lattice sandwich structures are fabricated by using BCC and the optimized BCT lattice structure as sandwich cores.And the dynamic impact process of steel ball with the lattice structures are simulated by finite element method.The reliability of the optimized design structures is further verified by comparing and analysing the response of lattice structures to the steel ball and the failure mechanism,providing a theoretical reference for the design of light lattice structure materials and practical engineering applications.