Optimization Of Low Velocity Impact Performance Of BCC Sandwich Plate And Analysis On Model Simplification

Body Centered Cubic(BCC)sandwich plate is a kind of double-plates sandwich structure.Due to its excellent mechanical and physical properties such as high strength and toughness,impact resistance,lightweight and good heat dissipation,it is widely used in aerospace,bio-medical,high-speed railway and automobile.Theoretically,the optimized design of the core structure of BCC sandwich plate can further improve its mechanical properties.However,due to the periodic characteristics and complex configuration of BCC core layer,it is difficult for the existing topological optimization algorithm to directly topological optimization design.As a result,the mechanical properties of the BCC core layer cannot be greatly improved.In recent years,the proposal of microstructure and its application in topological optimization design provide a reference scheme for topological optimization design of BCC core layer.Microstructure is a tiny part of macroscopic structure,and its configuration is simple and representative compared with macroscopic structure.Therefore,topology optimization of microstructure can effectively avoid the problem of complex configuration and difficult topology.The optimization concept of microstructure is suitable to deal with the core layer optimization of BCC sandwich plate.Therefore,in this thesis,the BCC sandwich plate is studied from the macro view to the micro view,and a BCC cell is selected from the BCC core layer to conduct topological optimization design.In order to reduce the calculation amount of simulation analysis,the optimization model is simplified by using the homogenization method.Firstly,in order to ensure the translational symmetry of the optimization process of BCC cell,periodic boundary conditions were established for the boundary surface of BCC cell before topological optimization.The purpose of optimization is to improve the impact deformation resistance of BCC structure when it is used as the sandwich plate,and the improvement of core layer stiffness will improve the plastic yield resistance of sandwich plate.Therefore,this thesis took the maximum stiffness of BCC cell as the optimization goal,and achieved the optimal stiffness design of BCC cell through ESO algorithm.The quasi-static tensile properties of topological optimization BCC cell was compared with those of other common BCC cells,it is found that the equivalent tensile modulus of topological optimization BCC cell is significantly improved compared with other BCC cells.After topological optimization of periodic cell,array expansion of topological optimization BCC cell,it can be used together with plates to generate topological optimization BCC sandwich plate.Then,3D printing and other processes were used to manufacture topological optimization BCC sandwich plate.Because low-velocity impact performance is one of the main mechanical properties of BCC sandwich plate,the low-velocity impact test and simulation analysis of topological optimization BCC sandwich plate were carried out by XBL-300 impact testing machine and ABAQUS finite element software.By comparing the experiment and simulation results,the accuracy of the simulation model of topological optimization BCC sandwich plate is verified.Then,the plate pit depth and plate pit area of topological optimization BCC sandwich plate and traditional BCC sandwich plate after low-velocity impact were compared and analyzed from different impact energy,impact angle and punch shape.It is found that the anti-deformation performance of topological optimization BCC sandwich plate after low velocity impact is significantly improved compared with that of traditional BCC sandwich plate,indicating that the topological optimization design at the cell scale has a great correlation with the improvement of mechanical properties of macroscopic BCC structure.After analyzing the impact history of two kinds of BCC sandwich plates,it is found that the topological optimization BCC sandwich plate has the advantage of anti-deformation performance over traditional BCC sandwich plate in the elastic recovery stage.In the low-velocity impact analysis of topological optimization BCC sandwich plate,the complexity of topological optimization BCC core layer configuration greatly increases the computational burden of simulation analysis.In order to simplify the simulation model,the equivalent elastic-plastic parameters of topological optimization BCC cell were extracted by homogenization method,and then the complex topological optimization BCC cell was transformed into homogeneous cell with very simple configuration.The accuracy of homogenization BCC cell simulation model was analyzed under periodic boundary conditions,and it is found that the accuracy of simulation results could still be guaranteed after homogenization BCC cell.Then the simplified model from a cell structure was applied to the BCC core layer,through the analysis of the flat pressure,it is found that the relative error between the force-displacement curve of the homogenization model and that of the fine model is within 15%,and the relative error of flat pressure energy absorption value within 10%,the analysis time of homogenization model is reduced by 17.4times compared with that of fine model.Finally,the model of the simplified method was applied to the topological optimization of BCC sandwich plate of low velocity impact analysis,it is found that the homogenization model can simulate the topological optimization of BCC sandwich plate in the process of low velocity impact force-time curve and energy absorption,the analysis time of topological optimization BCC sandwich plate homogenization model is much less than that of fine model.The homogenization method is suitable for simplified model analysis of complex BCC configuration.