Research On The Deformation Instability And Energy Absorption Of Single-cell And Multi-cell Metal Structures Under Axial Compression

Single-cell metal structures(various shapes of thin-walled metal tubes)and multicell metal structures(honeycomb structures,foam structures,etc.)as excellent buffering and energy absorbing structures,have been widely used in aerospace,transportation,military and other engineering fields due to their light weight,low relative density,high specific strength,high specific stiffness,and stable energy absorption characteristics.The buffered energy absorbing structures mainly absorb energy through compression deformation when subjected to various loads.Therefore,it is of great significance to study the instability deformation mode and energy absorption characteristics of the structures under axial compression conditions.This article focuses on three types of single-cell structures and two types of multi-cell structures.By conducting quasi-static compression tests and dynamic compression tests,the axial compression mechanical behavior of structures was studied,and the deformation mechanisms and characteristics of various structures were systematically analyzed using finite element software.The main research content of this article is as follows:(1)Study on the single-cell metal structure firstly.Three types of thin-walled metal tubes with circular,square,and hexagonal shapes were selected.By conducting quasistatic compression tests and dynamic compression tests at multiple strain rates,the instability deformation modes,buffering and energy absorption characteristics,and mechanical responses of the three types of single-cell structures under different loading conditions were studied.By comparing the experimental results fully,it was found that the deformation modes of square tube and hexagonal tube under static and dynamic loads were more stable,and the mechanical parameters of circular tube changed more regularly.The energy absorption capacity of hexagonal tube and circular tube was stronger and higher than that of square tube.Furthermore,dynamic finite element software was used to simulate the compression process of three types of single-cell metal structures under dynamic loads,and the deformation mechanism of the structure was analyzed.(2)A new type of composite circular honeycomb structure was proposed based on comparative analysis of previous methods for making circular honeycomb structures and research on circular single cell structures.The combination method consisting of two different material combinations,steel-aluminum and aluminum-aluminum.Through a series of axial compression tests,it was found that the composite circular honeycomb structure exhibits unified deformation modes under static and dynamic loads respectively.And the circular honeycomb structures made of steel-aluminum materials with better plasticity and higher strength not only have more stable deformation process and higher deformation degree,but also have better energy absorption performance.At the same time,further analysis is conducted by introducing the influence of mass specific energy absorption rate on the quality of different material combination methods.(3)A hexagonal honeycomb structure with controllable deformation was designed through 3D printing method.Four different deformation modes were achieved by performing quasi static compression tests and dynamic compression tests at two loading speeds respectively,including deformation from the position of the structure near the loading end,deformation from the position near the fixed end,deformation from the middle of the structure,and deformation from the positions at both ends of the structure.And,the impact of different deformation modes on their buffer energy absorption characteristics and mechanical parameters is further analyzed.The dynamic impact process of hexagonal honeycomb structures is simulated using numerical simulation methods to analyze their deformation characteristics.A hexagonal honeycomb structure with controllable deformation was designed using 3D printing method.Four different deformation modes were achieved by conducting axial compression tests on the structure under different loading conditions.Including the yielding deformation near the loading end,the deformation near the fixed end,the deformation starting from the middle of the structure,and the deformation starting from the two ends of the structure.Through further analysis,it is found that different deformation modes will have corresponding effects on the buffering and energy absorption characteristics and mechanical parameters of the structures.Numerical simulation methods are used to simulate the dynamic compression process of hexagonal honeycomb structures with the same size and matrix material,and their deformation characteristics are analyzed.This thesis includes 51 figures,21 tables,and 122 references.