Compressive Behavior of Porous Metals with Aligned Unidirectional Pores Compressed in the Direction Perpendicular to the
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INTRODUCTION
IT is expected that porous metals can be used as shock absorbers owing to their high energy absorption capabilities during compressive deformation.[1] The compressive stress–strain curve of porous metals comprises a plateau region where the compressive stress is nearly constant. The energy absorption capabilities of porous metals are determined by the features of the plateau region such as the plateau stress, strain range, and smoothness. In the case of porous metals being used as energy absorbers, the ideal-curve plateau region is flat
TOMOYA TAMAI, DAIKI MUTO, TOMONORI YOSHIDA, and MAHIRO SAWADA are with the Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 1698555, Japan. Contact e-mail: [email protected] SHINSUKE SUZUKI is with the Faculty of Science and Engineering, Waseda University and also with the Kagami Memorial Research Institute of Materials Science and Technology, Waseda University, 2-28-26 Nishiwaseda, Shinjuku, Tokyo 169-0051, Japan. MATEJ VESENJAK and ZORAN REN are with the Faculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, Slovenia. Manuscript submitted December 22, 2018. Article published online March 13, 2019 METALLURGICAL AND MATERIALS TRANSACTIONS A
and has a long strain range, no initial peak stress, and a large plateau stress in the stress range wherein the packaged object is not damaged.[2] Therefore, it is important to investigate the plateau region for the practical use of porous metals. According to the International Standards Organization (ISO) 13314, the plateau stress is the arithmetical mean of stresses between 20 and 30 pct or 20 and 40 pct compressive strains.[3] Plateau end is also defined as the point in the stress–strain curve at which the stress is 1.3 times the plateau stress. However, these are empirical definitions and are not derived from the deformation behavior. Thus, the compressive deformation behavior of porous metals that constitutes the plateau region should be investigated. The construction of simple deformation models is effective for the investigation of the compressive deformation behavior of porous metals. Many deformation models of cellular solids including porous metals have been developed based on periodic unit cells. Gibson and Ashby modeled a cellular solid as cubic-structured uniform struts and analyzed the buckling and plastic collapse stress as the initiation of plateau region.[4] Based on the model, the effects of the distribution of the solid between the cell faces and edges on the mechanical properties were studied by Simone and Gibson.[5]
VOLUME 50A, MAY 2019—2189
Deformation models of honeycombs having regular and two-dimensional structures have also been developed.[6,7] Harders et al. studied the influence of the cell wall shapes and density on the mechanical behavior of honeycombs.[8] Karagiozova and Yu[9] investigated the plastic deformation models of regular honeycomb structures under in-plane biaxial compression. However, these models were applied whe
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