Lightweight Optimization Design Of Space Bar Lattice Filled Energy Absorbing Box Structure

Most of the casualties caused by automobile traffic accidents occur in the frontal collision of automobiles.The energy-absorbing box can effectively dissipate the collision energy in the frontal collision of automobiles.Finding an energy absorption box with excellent energy absorption performance through optimal design is very important to improve the vehicle frontal collision performance.With the increasingly stringent environmental protection regulations,reducing emissions has become the mainstream of the industry.Lightweight design is the main means of energy conservation and emission reduction.While improving the crashworthiness of the energy absorption box,reducing the weight of the energy absorption box can achieve the goal of energy conservation.The main research contents of this paper are as follows:Firstly,the unit cell structure of spatial lattice is proposed.After the unit cell structure is copied,rotated and array,the spatial rod lattice structure is formed.The spatial lattice structure is meshed,given materials and set boundary conditions,and the finite element model of the spatial lattice structure is established.The energy absorption performance of the spatial lattice structure and several traditional lattice structures is compared and analyzed by finite element method.The theoretical analysis model of platform stress of the spatial lattice structure under quasi-static crushing condition is deduced,and the accuracy of the theoretical model is verified by numerical calculation method.The impact of the single cell of the spatial lattice structure on the crashworthiness of the lattice structure formed by a series of transformations under the change of a single geometric parameter is studied,which lays a foundation for the subsequent design of the geometric size range of the single cell of the energy absorbing box filled lattice structure.Secondly,in order to determine the cell size of the spatial lattice structure with the best crashworthiness,and the lattice structure can be put into the energy absorption box of a specific size,the cell size of the spatial lattice structure and the number of cells in X,Y and Z directions are taken as the design variables,the mass and overall size of the lattice structure are taken as the constraints,and the maximum mass specific energy absorption and the minimum peak force are taken as the optimization objectives,The second generation non dominated sorting genetic algorithm（NSGA-Ⅱ）is used to optimize the crashworthiness of the lattice structure.Then,based on the grey correlation analysis method and entropy weight method,the optimal array structure scheme is determined from the optimized Pareto solution set.Then,the optimized lattice structure sample and its material test sample are prepared by using the additive manufacturing technology,and the material tensile test is carried out according to the test method specified in the national standard to determine the mechanical parameters of the material.The finite element model of drop hammer impact lattice structure sample is established,and then the drop hammer impact test is carried out on the lattice structure sample.The drop hammer impact test results verify the accuracy of the numerical calculation model.Finally,the aforementioned optimal lattice structure was filled into the energy absorbing box,and the responses of the unfilled energy absorbing box and the energy absorbing box filled with the lattice structure during crushing were compared.The influence of the recessed direction of the induction groove of the energy-absorbing box on the energy-absorbing characteristics of the lattice-structured energy-absorbing box was also studied.Taking the gradient parameters of the lattice structure and the plate thickness of the energy absorbing box as the design variables,the peak force as the constraint condition,and the minimum mass ratio energy absorption,the maximum average collision force and the minimum mass as the objectives,the multi-objective lightweight optimization design of the energy absorbing box of the lattice structure is carried out.The results show that the performance of the optimized gradient lattice structure energy absorbing box is better than that of the initial energy absorbing box,The energy absorbing box with lattice structure has the advantages of light weight and energy absorption at the same time.The research results of this paper also have a certain reference for the lightweight design of lattice structure filled with other parts.