Effect of entrapped gas on the dynamic compressive behaviour of cellular solids

INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES

卷:63

Article

Sun, Yongle¹  Li, Q. M.^1,2 

[1] Univ Manchester, Sch Mech Aerosp & Civil Engn, Manchester M13 9PL, Lancs, England

[2] Beijing Inst Technol, Key State Lab Explos Sci & Technol, Beijing 100081, Peoples R China

关键词: Cellular materials;    Dynamic crushing;    Entrapped gas effect;    Modelling;   

DOI  :  10.1016/j.ijsolstr.2015.02.034

来源: Elsevier

【 摘 要 】

This study is aimed to clarify the effect of entrapped gas on the dynamic crushing of 2D cellular structures in order to gain general insights into the associated mechanisms for cellular solids. An analytical method is proposed to determine the critical strain-rates for adiabatic and isothermal processes of the entrapped gas. The crushing processes at various strain-rates are simulated using finite element method with considering the effect of the entrapped gas pressure on the solid cell deformation. A higher-order strain term is introduced into the equations derived from the Gibson-Ashby approach to improve the analytical prediction at large deformation. The numerical results show that the gas effect is significant at the densification stage wherein the crushing stress can be remarkably enhanced. The stress enhancement can arise from not only the direct contribution of gas pressure but also its indirect effect on the cell deformation and cell-wall interaction, depending on the range of strain-rates. Moreover, the entrapped gas can reduce the densification strain, which is important at intermediate strain-rates; whereas other mechanical factors (e.g. inertia and shock) associated with the dynamic crushing generally increase the densification strain and their influence becomes dominant at high strain-rates. At the plateau stage, the crushing stress is hardly affected by the entrapped gas, although the gas pressure in locally crushed cells could be appreciably high and deformation bands with less compaction can be produced. The numerical results also show that the gas effect is dependent on cell morphology. The comparison between the numerical and analytical predictions indicates that great caution should be taken when the Gibson-Ashby approach is used to estimate the stress enhancement in dynamic crushing, and numerical models may be necessary to realise the complex effect of the entrapped gas on the compressive behaviour of cellular solids. (C) 2015 Elsevier Ltd. All rights reserved.

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