The University of Southampton
University of Southampton Institutional Repository

Deformation mechanisms of idealised cermets under multi-axial loading

Deformation mechanisms of idealised cermets under multi-axial loading
Deformation mechanisms of idealised cermets under multi-axial loading
The response of idealised cermets comprising approximately 60% by volume steel spheres in a Sn/Pb solder matrix is investigated under a range of axisymmetric compressive stress states. Digital volume correlation (DVC) analysis of X-ray micro-computed tomography scans (?-CT), and the measured macroscopic stress-strain curves of the specimens revealed two deformation mechanisms. At low triaxialities the deformation is granular in nature, with dilation occurring within shear bands. Under higher imposed hydrostatic pressures, the deformation mechanism transitions to a more homogeneous incompressible mode. However, DVC analyses revealed that under all triaxialities there are regions with local dilatory and compaction responses, with the magnitude of dilation and the number of zones wherein dilation occurs decreasing with increasing triaxiality. Two numerical models are presented in order to clarify these mechanisms: (i) a periodic unit cell model comprising nearly rigid spherical particles in a porous metal matrix and (ii) a discrete element model comprising a large random aggregate of spheres connected by non-linear normal and tangential “springs”. The periodic unit cell model captured the measured stress-strain response with reasonable accuracy but under-predicted the observed dilation at the lower triaxialities, because the kinematic constraints imposed by the skeleton of rigid particles were not accurately accounted for in this model. By contrast, the discrete element model captured the kinematics and predicted both the overall levels of dilation and the simultaneous presence of both local compaction and dilatory regions with the specimens. However, the levels of dilation in this model are dependent on the assumed contact law between the spheres. Moreover, since the matrix is not explicitly included in the analysis, this model cannot be used to predict the stress-strain responses. These analyses have revealed that the complete constitutive response of cermets depends both on the kinematic constraints imposed by the particle aggregate skeleton, and the constraints imposed by the metal matrix filling the interstitial spaces in that skeleton.
Cermets, Digital volume correlation, Discrete element, Kinematic constraints, Micro-computed tomography, Porous plasticity
0022-5096
80-100
Bele, E.
01a4e564-7c8a-42d3-b96d-c2ddf8c9e936
Goel, A.
1038ce0a-bbcc-465d-9f46-17f5652bd711
Pickering, E. G.
3487939e-34c0-488a-8c75-780bf0192039
Borstnar, G.
4b0498bf-6b1c-4e11-bd0a-7be326e8e837
Katsamenis, O. L.
8553e7c3-d860-4b7a-a883-abf6c0c4b438
Pierron, F.
a1fb4a70-6f34-4625-bc23-fcb6996b79b4
Danas, K.
d5083844-299d-42c8-b744-93a07982f24e
Deshpande, V. S.
10c6023e-5876-4f50-b1a3-d14d79d667b2
Bele, E.
01a4e564-7c8a-42d3-b96d-c2ddf8c9e936
Goel, A.
1038ce0a-bbcc-465d-9f46-17f5652bd711
Pickering, E. G.
3487939e-34c0-488a-8c75-780bf0192039
Borstnar, G.
4b0498bf-6b1c-4e11-bd0a-7be326e8e837
Katsamenis, O. L.
8553e7c3-d860-4b7a-a883-abf6c0c4b438
Pierron, F.
a1fb4a70-6f34-4625-bc23-fcb6996b79b4
Danas, K.
d5083844-299d-42c8-b744-93a07982f24e
Deshpande, V. S.
10c6023e-5876-4f50-b1a3-d14d79d667b2

Bele, E., Goel, A., Pickering, E. G., Borstnar, G., Katsamenis, O. L., Pierron, F., Danas, K. and Deshpande, V. S. (2017) Deformation mechanisms of idealised cermets under multi-axial loading. Journal of the Mechanics and Physics of Solids, 102, 80-100. (doi:10.1016/j.jmps.2017.01.002).

Record type: Article

Abstract

The response of idealised cermets comprising approximately 60% by volume steel spheres in a Sn/Pb solder matrix is investigated under a range of axisymmetric compressive stress states. Digital volume correlation (DVC) analysis of X-ray micro-computed tomography scans (?-CT), and the measured macroscopic stress-strain curves of the specimens revealed two deformation mechanisms. At low triaxialities the deformation is granular in nature, with dilation occurring within shear bands. Under higher imposed hydrostatic pressures, the deformation mechanism transitions to a more homogeneous incompressible mode. However, DVC analyses revealed that under all triaxialities there are regions with local dilatory and compaction responses, with the magnitude of dilation and the number of zones wherein dilation occurs decreasing with increasing triaxiality. Two numerical models are presented in order to clarify these mechanisms: (i) a periodic unit cell model comprising nearly rigid spherical particles in a porous metal matrix and (ii) a discrete element model comprising a large random aggregate of spheres connected by non-linear normal and tangential “springs”. The periodic unit cell model captured the measured stress-strain response with reasonable accuracy but under-predicted the observed dilation at the lower triaxialities, because the kinematic constraints imposed by the skeleton of rigid particles were not accurately accounted for in this model. By contrast, the discrete element model captured the kinematics and predicted both the overall levels of dilation and the simultaneous presence of both local compaction and dilatory regions with the specimens. However, the levels of dilation in this model are dependent on the assumed contact law between the spheres. Moreover, since the matrix is not explicitly included in the analysis, this model cannot be used to predict the stress-strain responses. These analyses have revealed that the complete constitutive response of cermets depends both on the kinematic constraints imposed by the particle aggregate skeleton, and the constraints imposed by the metal matrix filling the interstitial spaces in that skeleton.

Text
1-s2.0-S0022509616308146-main.pdf - Accepted Manuscript
Download (2MB)
Text
JMPS_2016_final.pdf - Accepted Manuscript
Download (3MB)

More information

Accepted/In Press date: 6 January 2017
e-pub ahead of print date: 10 January 2017
Published date: 1 May 2017
Keywords: Cermets, Digital volume correlation, Discrete element, Kinematic constraints, Micro-computed tomography, Porous plasticity
Organisations: University of Southampton, Faculty of Engineering and the Environment

Identifiers

Local EPrints ID: 404736
URI: https://eprints.soton.ac.uk/id/eprint/404736
ISSN: 0022-5096
PURE UUID: e4d07444-2395-4731-a3d9-c718d9afb07c
ORCID for O. L. Katsamenis: ORCID iD orcid.org/0000-0003-4367-4147
ORCID for F. Pierron: ORCID iD orcid.org/0000-0003-2813-4994

Catalogue record

Date deposited: 20 Jan 2017 15:00
Last modified: 06 Jun 2018 12:34

Export record

Altmetrics

Contributors

Author: E. Bele
Author: A. Goel
Author: E. G. Pickering
Author: G. Borstnar
Author: F. Pierron ORCID iD
Author: K. Danas
Author: V. S. Deshpande

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×