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Ultra high speed full-field deformation measurements on concrete spalling specimens and stiffness identification with the Virtual Fields Method

Ultra high speed full-field deformation measurements on concrete spalling specimens and stiffness identification with the Virtual Fields Method
Ultra high speed full-field deformation measurements on concrete spalling specimens and stiffness identification with the Virtual Fields Method
For one decade, spalling techniques based on the use of a metallic Hopkinson bar in contact with a concrete sample have been widely employed to characterise the dynamic tensile strength of concrete at strain rates ranging from a few tens to hundreds of s-1.
However, the processing method based on the use of the velocity profile measured on the rear free surface of the sample (Novikov formula) remains quite basic. In particular, the identification of the whole softening behaviour of the concrete material is currently out of reach. In the present paper, a new processing technique is proposed based on the use of the virtual fields method (VFM). First, a digital ultra-high-speed camera is used to record the pictures of a grid bonded onto the specimen. Then, images of the grid recorded by the camera are processed to obtain full-field axial displacement maps at the surface of the specimen. Finally, a specific virtual field has been defined in the VFM equation to use the acceleration map as an alternative ‘load cell’. This method applied to three spalling tests with different impact parameters allowed the identification of Young’s modulus during the test. It was shown that this modulus is constant during the initial compressive part of the test and
decreases in the tensile part when microdamage exists. It was also shown that in such a simple inertial test, it was possible to reconstruct average axial stress profiles using only the acceleration data. It was then possible to construct local stress–strain curves and derive a tensile
strength value.
1475-1305
388-405
Pierron, F.
a1fb4a70-6f34-4625-bc23-fcb6996b79b4
Forquin, P.
b93d9562-887e-4e3c-9821-0ecaa351f0c5
Pierron, F.
a1fb4a70-6f34-4625-bc23-fcb6996b79b4
Forquin, P.
b93d9562-887e-4e3c-9821-0ecaa351f0c5

Pierron, F. and Forquin, P. (2012) Ultra high speed full-field deformation measurements on concrete spalling specimens and stiffness identification with the Virtual Fields Method. Strain, 28 (5), 388-405. (doi:10.1111/j.1475-1305.2012.00835.x).

Record type: Article

Abstract

For one decade, spalling techniques based on the use of a metallic Hopkinson bar in contact with a concrete sample have been widely employed to characterise the dynamic tensile strength of concrete at strain rates ranging from a few tens to hundreds of s-1.
However, the processing method based on the use of the velocity profile measured on the rear free surface of the sample (Novikov formula) remains quite basic. In particular, the identification of the whole softening behaviour of the concrete material is currently out of reach. In the present paper, a new processing technique is proposed based on the use of the virtual fields method (VFM). First, a digital ultra-high-speed camera is used to record the pictures of a grid bonded onto the specimen. Then, images of the grid recorded by the camera are processed to obtain full-field axial displacement maps at the surface of the specimen. Finally, a specific virtual field has been defined in the VFM equation to use the acceleration map as an alternative ‘load cell’. This method applied to three spalling tests with different impact parameters allowed the identification of Young’s modulus during the test. It was shown that this modulus is constant during the initial compressive part of the test and
decreases in the tensile part when microdamage exists. It was also shown that in such a simple inertial test, it was possible to reconstruct average axial stress profiles using only the acceleration data. It was then possible to construct local stress–strain curves and derive a tensile
strength value.

Full text not available from this repository.

More information

Published date: May 2012
Organisations: Engineering Mats & Surface Engineerg Gp

Identifiers

Local EPrints ID: 346985
URI: https://eprints.soton.ac.uk/id/eprint/346985
ISSN: 1475-1305
PURE UUID: ef7a8b8e-8cb7-4076-b235-bf969383473d
ORCID for F. Pierron: ORCID iD orcid.org/0000-0003-2813-4994

Catalogue record

Date deposited: 23 Jan 2013 15:09
Last modified: 08 Oct 2019 00:42

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