The strain rate effect of an open cell aluminum foam
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I. INTRODUCTION
METALLIC foams have emerged as a class of materials with unique macroscopic pore structure, low density, and high strength, which makes them prospective candidates in lightweight structures and energy absorbing devices.[1,2,3] For such applications, understanding their mechanical behavior, particularly their response to dynamic loading is of strong importance to the engineering community. A number of experimental, numerical, and theoretical studies have been directed toward these topics in the last decade and much knowledge has been obtained. However, previous studies have led to conflicting conclusions on the effect of impact velocity or strain rate on the compressive behavior of the metallic foams.[4–14] Mukai et al.,[6,9] Kathryn et al.,[7] and Paul and Ramamurty[8] found the flow stress of a closed cell aluminum foam to increase with the increasing strain rate, while Lankford and Dannemann,[5] Deshpande and Fleck,[10] Hall et al.,[11] and most other researchers addressed no strain-rate sensitivity in the closed-cell aluminum foams under both quasi-static and dynamic loadings. Moreover, the strain rate effect seems to be independent of whether the cell is open or closed, and of the cell wall materials. For instance, Lankford and Dannemann[5] and Deshpande and Fleck[10] demonstrated that the dependence of dynamic compressive strength on the loading rate was negligible for a low-density open cell 6061 Al foam, while Kanahashi and Mukai also showed evidence that the strength of an open cell SG91A aluminum foam increased with increasing strain rate.[9] Although there seems to be no general trend in the strain rate sensitivity of metal foams, it has been found that such factors as morphology of the cells, composition of the cell wall materials, density of the metal foams, and impact direction do have influence over it.[12,13] It follows that further investigations are necessary to detect the origin of strain rate dependence in the material. In the present study, the strain rate effect on the dynamic compressive behavior of an open-cell commercially pure aluminum foam was investigated both experimentally and analytically with the objective of establishing a mechanical model applicable to a relatively broad range of strain rate FUSHENG HAN, Professor, is with the Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, Anhui 230031, P.R. China. Contact e-mail: [email protected] HEFA CHENG, Professor, and QIANG WANG, Lecturer, are with the School of Materials Engineering, Hefei University of Technology, Hefei, Anhui 230001, P.R. China. ZHIBIN LI, Lecturer, is with Shaoxing College, Shaoxing Zhejiang 312000, P.R. China. Manuscript submitted April 30, 2004. METALLURGICAL AND MATERIALS TRANSACTIONS A
and providing an insight into the dependence of the deformation and flow stress of the foam on the strain rate. II. EXPERIMENTAL PROCEDURE The aluminum foams used in this study were fabricated with commercially pure aluminum via the infiltration process. The pr
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