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Identification of viscoplastic parameters and characterization of Lüders behaviour using digital image correlation and the virtual fields method

Identification of viscoplastic parameters and characterization of Lüders behaviour using digital image correlation and the virtual fields method
Identification of viscoplastic parameters and characterization of Lüders behaviour using digital image correlation and the virtual fields method
In this study, tensile loading experiments are performed on notched steel bars at an average applied strain rate of 1s-1. Displacement fields are measured across the specimen by coupling digital image correlation (DIC) with imaging using high speed CCD cameras (4796 fps). Results from the experiments indicate the presence of local strain rates ranging from 0.1 to 10s-1 in the notched specimens. The heterogeneity of the strain rate fields provides suitable conditions for determining simultaneously all the elasto-visco-plastic constitutive parameters governing the material behavior. For that, the whole stress fields are reconstructed in the specimen using the full-field deformation measurements. This reconstruction is repeated with different constitutive parameters until the average stress in the specimen matches the one measured with the load cell response. Perzyna’s model is firstly considered for the reconstruction of stresses but it is shown to be unsuited for providing the drop in the average stress that is systematically detected at the onset of plasticity by the load cell. This drop is attributed to the sudden occurrence of plasticity in the material due to Lüders effect. A modified model for elasto-visco-plasticity taking account of Lüders behavior in the material is considered afterwards. It yields a better agreement between the reconstructed stresses and the load cell response, and a more accurate identification of the parameters driving the visco-plastic model. Eventually, it is shown how to use DIC measurements for replacing the load cell measurements when the transient effects in the test reach the resonance frequency of the load cell
0167-6636
729-742
Avril, Stéphane
e7143b4a-693f-4c40-9aab-230102aa0017
Pierron, Fabrice
a1fb4a70-6f34-4625-bc23-fcb6996b79b4
Sutton, Michael A.
7db7d51d-ec5d-4088-9f5f-de87c02c62f8
Yan, Junhui
6bd04923-33b6-4850-a285-bb7da9081feb
Avril, Stéphane
e7143b4a-693f-4c40-9aab-230102aa0017
Pierron, Fabrice
a1fb4a70-6f34-4625-bc23-fcb6996b79b4
Sutton, Michael A.
7db7d51d-ec5d-4088-9f5f-de87c02c62f8
Yan, Junhui
6bd04923-33b6-4850-a285-bb7da9081feb

Avril, Stéphane, Pierron, Fabrice, Sutton, Michael A. and Yan, Junhui (2008) Identification of viscoplastic parameters and characterization of Lüders behaviour using digital image correlation and the virtual fields method. Mechanics of Materials, 40 (9), 729-742. (doi:10.1016/j.mechmat.2008.03.007).

Record type: Article

Abstract

In this study, tensile loading experiments are performed on notched steel bars at an average applied strain rate of 1s-1. Displacement fields are measured across the specimen by coupling digital image correlation (DIC) with imaging using high speed CCD cameras (4796 fps). Results from the experiments indicate the presence of local strain rates ranging from 0.1 to 10s-1 in the notched specimens. The heterogeneity of the strain rate fields provides suitable conditions for determining simultaneously all the elasto-visco-plastic constitutive parameters governing the material behavior. For that, the whole stress fields are reconstructed in the specimen using the full-field deformation measurements. This reconstruction is repeated with different constitutive parameters until the average stress in the specimen matches the one measured with the load cell response. Perzyna’s model is firstly considered for the reconstruction of stresses but it is shown to be unsuited for providing the drop in the average stress that is systematically detected at the onset of plasticity by the load cell. This drop is attributed to the sudden occurrence of plasticity in the material due to Lüders effect. A modified model for elasto-visco-plasticity taking account of Lüders behavior in the material is considered afterwards. It yields a better agreement between the reconstructed stresses and the load cell response, and a more accurate identification of the parameters driving the visco-plastic model. Eventually, it is shown how to use DIC measurements for replacing the load cell measurements when the transient effects in the test reach the resonance frequency of the load cell

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e-pub ahead of print date: March 2008
Published date: September 2008
Organisations: Engineering Mats & Surface Engineerg Gp

Identifiers

Local EPrints ID: 209667
URI: https://eprints.soton.ac.uk/id/eprint/209667
ISSN: 0167-6636
PURE UUID: 585484b7-4d5b-400e-b26b-f458f8cad757
ORCID for Fabrice Pierron: ORCID iD orcid.org/0000-0003-2813-4994

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Date deposited: 01 Feb 2012 15:25
Last modified: 12 Nov 2019 01:42

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