Design On Energy Absorption For Thin Wall Multicellular Structures Of The Local Surface Nanocrystallization

Safety issues in collisions and impacts between vehicles are very important issues.How to effectively absorb energy and protect the safety of personnel and property in the event of a collision has always attracted attention and has become a hot research field.Energy absorption device is a main way to protect the safety of personnel and critical equipment.The thin-walled tube structure has the advantages of economy,effectiveness,and reliability in absorbing energy,and is widely used in vehicles such as automobiles,such as energy-absorbing boxes.The energy absorption effect of the thin-walled tube structure is directly related to its structural form,buckling mode and deformation evolution path.The main methods currently used are prefabricated initial shapes,indentation openings or additional baffle structures,etc.,in an attempt to improve the specific energy absorption effect.These design methods will change the integrity and aesthetics of the structure to a certain extent,reduce the overall strength of the structure,and increase the quality of the structure.Therefore,new technologies and methods need to be introduced in the design of energy absorbing devices.In this thesis,local surface nanotechnology is introduced into the multicellular thin-walled structure.With the help of local surface nanocrystallization to change the local mechanical properties of the structure,the buckling deformation and development path of the multicellular thin-walled structures under impact are induced and controlled,so as to improve the structure and the goal of energy absorption indicators.In this thesis,finite element numerical simulation is the main research tool and method,the local surface nanocrystallization multicellular thin-walled tube structure is used as the research object and the specific energy absorption(SEA)is used as an index to evaluate the energy absorption of the structure,and the problem is researched and analyzed.In the numerical simulation,the energy absorbed by the structure is obtained through the impact load-displacement curve,so that the specific energy absorption index can be obtained.First,analyze the buckling deformation and development path of non-nanocrystallization single tube and multicellular thin-walled tube under impact,and use this as a comparison object.Then design the local surface nanocrystallization layout of the multicellular thin-walled structure,and numerically simulate the buckling deformation of the structure under the impact load and evaluate the energy absorption during the buckling process.In the local surface nanocrystallization layout of the multicellular thin-walled structure,the outer plate of the multicellular structure adopts two layout modes,namely the anti-symmetric stripe mode and the staggered lattice mode.According to the topological characteristics of buckling deformation,the local surface nanocrystallization layout of the multicellular thin-walled structure proposes four nanocrystallization modes,including the antisymmetric stripe mode,the staggered lattice mode,the embedded lattice mode and the outer lattice pattern.mode.Numerical simulations under axial impact are carried out for a variety of different cell numbers,various nanocrystallization structured layouts and combinations of local surface nanocrystallization multicellular structures.The effects of different impact speeds and impact angles are analyzed.Based on the results of a large number of numerical simulations and the specific energy absorption as the evaluation index,the design scheme of the multicellular thin-walled structure with the local surface nanocrystallization was optimized.On this basis,the numerical analysis and design of the local surface nano-hollowed multicellular thin-walled structures are carried out.Numerical results show that the local surface nanocrystallization can induce the buckling mode of the structure during the impact process of the multicellular thin-walled structure,control the buckling deformation path and realize the progressive telescopic buckling deformation mode,and can greatly improve the energy absorption index of the structures.It can be seen that the specific energy absorption,the buckling deformation mode and the buckling deformation process of the structure are closely related to the local surface nanocrystallization structured layout.The results also show that the local surface nanocrystallization layout is not as dense as possible,so there is an optimal nanocrystallization design.The optimization results show that the specific energy absorption of the multicellular structure with the optimized local surface nanocrystallization layout is699.41% higher than that of the non-nanocrystallization single tube,and 57.00% higher than the same multicellular structure without nanocrystallization.Therefore,the local surface nanocrystallization multicellular structure has important application prospects,and provides a basis and design ideas for the design of energy absorbing devices.