Title: Mapping local deformation behavior in single cell metal lattice structures

Abstract

The deformation behavior of metal lattice structures is extremely complex and challenging to predict, especially since strain is not uniformly distributed throughout the structure. Understanding and predicting the failure behavior for these types of light-weighting structures is of great interest due to the excellent scaling of stiffness- and strength-to weight ratios they display. Therefore, there is a need to perform simplified experiments that probe unit cell mechanisms. This study reports on high resolution mapping of the heterogeneous structural response of single unit cells to the macro-scale loading condition. Two types of structures, known to show different stress-strain responses, were evaluated using synchrotron radiation micro-tomography while performing in-situ uniaxial compression tests to capture the local micro-strain deformation. These structures included the octet-truss, a stretch-dominated lattice, and the rhombic-dodecahedron, a bend-dominated lattice. The tomographic analysis showed that the stretch- and bend-dominated lattices exhibit different failure mechanisms and that the defects built into the structure cause a heterogeneous localized deformation response. Also shown here is a change in failure mode for stretch-dominated lattices, where there appears to be a transition from buckling to plastic yielding for samples with a relative density between 10 and 20%. The experimental results were also used to informmore » computational studies designed to predict the mesoscale deformation behavior of lattice structures. Here an equivalent continuum model and a finite element model were used to predict both local strain fields and mechanical behavior of lattices with different topologies.« less

Authors:

Carlton, Holly D. ^[1]; Lind, Jonathan ^[1]; Messner, Mark C.  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-0040-4385"

Volkoff-Shoemaker, Nickolai A. ^[1]; Barnard, Harold S. ^[2]; Barton, Nathan R. ^[1]; Kumar, Mukul ^[1]

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+ Show Author Affiliations

1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Publication Date:

Wed Feb 08 00:00:00 EST 2017

Research Org.:

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1396219

Alternate Identifier(s):

OSTI ID: 1397836; OSTI ID: 1476489

Report Number(s):

LLNL-JRNL-715679
Journal ID: ISSN 1359-6454

Grant/Contract Number:  

AC52-07NA27344; AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Acta Materialia

Additional Journal Information:

Journal Volume: 129; Journal Issue: C; Journal ID: ISSN 1359-6454

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

42 ENGINEERING; 36 MATERIALS SCIENCE; Mechanical properties; Lattice structure; Synchrotron radiation computed tomography; In situ compression test