Vol. 9, No. 2, 2014

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ISSN: 1559-3959
Dynamic compression of square tube cellular structures

Ryan L. Holloman, Karthikeyan Kandan, Vikram Deshpande and Haydn N. G. Wadley

Vol. 9 (2014), No. 2, 149–182
Abstract

Aluminum cellular structures have been fabricated by combining a two-dimensional [0/90]2 arrangement of square Al 6061-T6 alloy tubes with orthogonal tubes inserted in the out-of-plane direction. By varying the tube wall thickness, the resulting three-dimensional cellular structures had relative densities between 11 and 43%. The dynamic compressive response of the three-dimensional cellular structure, and the two-dimensional [0/90]2 array and out-of-plane tubes from which they were constructed, have been investigated using a combination of instrumented Kolsky bar impact experiments, high-speed video imaging, and finite element analysis. We find the compression rate has no effect upon the strength for compression strain rates up to 2000 s1, despite a transition to higher-order buckling modes at high strain rates. The study confirms that a synergistic interaction between the colinear aligned and out-of-plane tubes, observed during quasistatic loading, extends to the dynamic regime. Finite element simulations, using a rate-dependent, piecewise linear strain hardening model with a von Mises yield surface and an equivalent plastic strain failure criterion, successfully predicted the buckling response of the structures, and confirmed the absence of strain-rate hardening in the three-dimensional cellular structure. The simulations also reveal that the ratio of the impact to back-face stress increased with strain rate and relative density, a result with significant implications for shock-load mitigation applications of these structures.

Keywords
cellular structures, 6061 aluminum, impact testing, dynamic loads, material rate-dependence
Milestones
Received: 27 July 2013
Accepted: 26 December 2013
Published: 30 May 2014
Authors
Ryan L. Holloman
Department of Materials Science and Engineering
University of Virginia
P.O. Box 400240, 351 McCormick Rd
Charlottesville, VA 22903-4240
United States
Karthikeyan Kandan
Department of Engineering
Cambridge University
Trumpington Street
Cambridge
CB2 1PZ
United Kingdom
Vikram Deshpande
Department of Engineering
Cambridge University
Trumpington Street
Cambridge
CB2 1PZ
United Kingdom
Haydn N. G. Wadley
Department of Materials Science and Engineering
University of Virginia
P.O. Box 400240, 351 McCormick Rd
Charlottesville, VA 22903-4240
United States