Analysis And Design Optimization Of The Lightweight Impact-Protection Structure

Vehicles in daily life are becoming heavier and faster,and the impact environment is harsher and harsher for military equipment,so the impact protection for the safety of the structures,the personnel and the equipment are more and more important.The impact protection capability is increasingly demanded.Thinking about the power and handing of the equipments,the weight of the structure should be also limited.Therefore,the deformation characteristics and energy absorption mechanism of the impact protection structures under impact loads should be analyzed,and then the improving method of the light-weight impact protective structures can be carried out,which is always a research hotspot.In this thesis,the collision impact and the explosion impact are considered,the design method of the impact protection structure is studied and the new light-weight configuration is proposed.For the axial impact case,the design method for improving the energy absorption of the thin-walled tube are studied.The thin-walled square tube with lateral piecewise variable thicknessand and the multi-cell square tube with lateral variable thickness are proposed,and the theoretical prediction formulations of their energy absorption properties are established.For the transverse impact case,the energy absorption properties of the thin-walled beams with internal filling is studied.The energy absorption improvement design of the thin-walled beam based on filling reinforcement structure is proposed,and the impact protection properties is analyzed.For the explosion impact protection,an optimum design method for improving the anti-shock properties of the grid sandwich plate based on topological optimization is proposed,and a graded grid sandwich plate is proposed.Considering the response stage of the sandwich plate subjected to out-of-plane dynamic compression,a grid sandwich plate structure with improved basic element is proposed,and the energy absorption of this grid sandwich plate is analyzed.The specific contents and results are as follows:(1)Properties analysis and optimization design of the lateral piecewise variable thickness(LPVT)thin-walled square tube under axial compression.Based on the energy dissipation mechanism of the thin-walled square tube under axial compression,a thin-walled square tube with the lateral piecewise variable thickness is proposed.The thicker thickness is adopted in the corner region to local strengthen the corner.Based on the super folding element method,the theoretical analysis of thin-walled square tubes with lateral piecewise variable thickness under axial compression is carried out,and the prediction formulation of the mean crushing force is deduced.The axial compression experimental and numerical simulation study of the LPVT and the uniform thickness square tubes are carried out.The effectiveness of the local strengthening design and the correctness of the prediction formulation are verified.The effects of section parameters on the axial compression properties of the LPVT thin-walled square tubes are discussed,and the section parameters are optimized.The energy absorption of the thin-walled square tube under axial compression can be significantly improved by the lateral piecewise variable thickness design.(2)Energy absorption analysis and optimization of the local strengthening multi-cell square tubes with lateral variable thickness under axial compression.The basic elements of the square multi-cell tube are classified,and the energy absorption properties of the different basic elements under axial compression are investigated.Based on the energy absorption efficiency difference among the basic elements,a square multi-cell tube with lateral variable thickness is proposed,and the lateral thickness distribution of the multi-cell square tube is optimized.The axial compression properties of the improved square multi-cell tube are investigated by theoretical and numerical analysis.The prediction formulation of the energy absorption properties is established.The theoretical and numerical results show the lateral variable thickness design based on energy absorption efficiency of the basic elements improve the energy absorption of the multi-cell square tube under axial compression a lot,and the theoretical prediction formulation can quickly and accurately predict the energy absorption properties of the multi-cell tube.Based on the lateral thickness distribution optimal results,a non-convex multi-cell design with lateral variable thickness is proposed,which has better energy absorption properties.(3)Improvement design for the energy absorption properties of the thin-walled square tube(beam)under transverse impact by filling reinforcement structures.The deformation mode of thin-walled square tube,multi-cell square tube and square tube with foam filler subject to transverse impact is studied.It is proposed to change the cross-section topology of thin-walled square tubes by filling reinforcement structures.The deformation mode can be changed through the interaction between reinforcement structures and thin-walled tubes.The connection between reinforcement structures and thin-walled tube is difficult to describe.Two connection conditions are considered,and other connections can be described by weighted summation method.The bending collapse of the square tubes with the filling reinforcement structures is studied by numerical method.The results show that the energy absorption properties and residual bending resistance of the tubes under transverse impact are improved by filling reinforcement structure,and the section design of the reinforcement structure can further improve the properties of the structure.(4)Design method of the grid sandwich plate for explosion protection.The influence of grid web parameters on the properties of the sandwich plate is analyzed theoretically.The equivalent relationship between the grid web parameters and the thickness of equivalent plate is established,and the sandwich plate can be equivalent to a solid plate with a thickness.The hybrid cellular automaton method is used to design the thickness distribution of the clamped equivalent plate under different loads.Based on the equivalent thickness distribution and the strain distribution in the orthogonal direction,the grid sandwich plate is divided into three in-plane functional regions and the webs are designed in different regions based on the relationship between the web parameters and the thickness of the equivalent plate.Based on this design method,four graded grid sandwich plates are proposed.The graded grid sandwich plates have good load-bearing and impact resistance properties.Compared with other methods,our design method has higher efficiency and lower requirements for initial design.(5)Properties analysis and optimization of the grid sandwich plate based on the basic element strengthened design under out-of-plane compression.The grid sandwich plate should be designed to improve its energy absorption properties under out-of-plane compression.Grid is composed of the crisscross elements arranged periodically,therefore the strengthening design for the basic element is considered.An improved grid sandwich plate based on the strengthened design of the basic element is proposed.Considering the geometric asymmetry of the crisscross element,the coefficient of geometric difference is proposed in theoretical analysis,and the formulation for predicting the out-of-plane compression properties of the improved grid sandwich plate is established.The out-of-plane compression properties of the improved grid sandwich plates is numerically analyzed,and the cross-section characteristic parameters of the grid sandwich plate are collaborative optimized.The out-of-plane compression properties improvement caused by only one parameter design is limited.Collaborative design of the cross-section parameters is an effective way to greatly improve the out-of-plane compression properties of the grid sandwich plate.