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An image-based approach for measuring dynamic fracture toughness

An image-based approach for measuring dynamic fracture toughness
An image-based approach for measuring dynamic fracture toughness

In order to model the dynamic failure of engineering structures it is necessary to have a thorough understanding of dynamic fracture processes. Dynamic fracture toughness has been experimentally analysed by fitting the K-dominant solution to the displacement field measured with a local or full-field technique, such as caustics, photoelasticity or digital image correlation. For highly dynamic crack propagation the stress state at the crack tip is influenced by stress waves. A dynamic propagating crack emits stress waves which can be reflected and/or scattered away. These waves are felt by the evolving crack front, as well as through the sample configuration, and hence material inertia may lead to effects more subtle (yet still present) than those associated with load transfer. The K-dominant solution only indirectly accounts for these inertial effects by including the crack velocity as an input or by using higher order terms in the series expansion. The aim of this work is to develop a new image-based method for measuring dynamic fracture toughness. This method uses full-field measurements to perform an energy balance on a fracture specimen and calculate the energy consumed by crack growth. Using full-field data the impact energy, strain energy and kinetic energy can be measured. When the material cracks the fracture energy is the difference between the impact energy and the sum of the strain and kinetic energy. Explicit dynamics simulations using cohesive elements were used to validate the methodology. The finite element data was used for simulated image deformation experiments. These virtual experiments were used to analyse measurement error propagation from camera spatial and temporal resolution. Future work will include additional image deformation simulations and a first experimental validation of the test method.

Dynamic fracture, Energy balance, Full-field measurement, Image-based methods, Ultra-high speed imaging
247-250
Springer
Fletcher, Lloyd
48dca64b-f93c-4655-9205-eaf4e74be90c
Lamberson, Leslie
7f3c2c2a-5b43-4312-821b-eb3e8d04dc19
Pierron, Fabrice
a1fb4a70-6f34-4625-bc23-fcb6996b79b4
Kimberley, J.
Lamberson, L.
Mates, S.
Fletcher, Lloyd
48dca64b-f93c-4655-9205-eaf4e74be90c
Lamberson, Leslie
7f3c2c2a-5b43-4312-821b-eb3e8d04dc19
Pierron, Fabrice
a1fb4a70-6f34-4625-bc23-fcb6996b79b4
Kimberley, J.
Lamberson, L.
Mates, S.

Fletcher, Lloyd, Lamberson, Leslie and Pierron, Fabrice (2018) An image-based approach for measuring dynamic fracture toughness. Kimberley, J., Lamberson, L. and Mates, S. (eds.) In Dynamic Behavior of Materials, Volume 1. Springer. pp. 247-250 . (doi:10.1007/978-3-319-95089-1_45).

Record type: Conference or Workshop Item (Paper)

Abstract

In order to model the dynamic failure of engineering structures it is necessary to have a thorough understanding of dynamic fracture processes. Dynamic fracture toughness has been experimentally analysed by fitting the K-dominant solution to the displacement field measured with a local or full-field technique, such as caustics, photoelasticity or digital image correlation. For highly dynamic crack propagation the stress state at the crack tip is influenced by stress waves. A dynamic propagating crack emits stress waves which can be reflected and/or scattered away. These waves are felt by the evolving crack front, as well as through the sample configuration, and hence material inertia may lead to effects more subtle (yet still present) than those associated with load transfer. The K-dominant solution only indirectly accounts for these inertial effects by including the crack velocity as an input or by using higher order terms in the series expansion. The aim of this work is to develop a new image-based method for measuring dynamic fracture toughness. This method uses full-field measurements to perform an energy balance on a fracture specimen and calculate the energy consumed by crack growth. Using full-field data the impact energy, strain energy and kinetic energy can be measured. When the material cracks the fracture energy is the difference between the impact energy and the sum of the strain and kinetic energy. Explicit dynamics simulations using cohesive elements were used to validate the methodology. The finite element data was used for simulated image deformation experiments. These virtual experiments were used to analyse measurement error propagation from camera spatial and temporal resolution. Future work will include additional image deformation simulations and a first experimental validation of the test method.

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More information

e-pub ahead of print date: 28 October 2018
Venue - Dates: SEM Annual Conference and Exposition on Experimental and Applied Mechanics, 2018, Greenville, United States, 2018-06-04 - 2018-06-07
Keywords: Dynamic fracture, Energy balance, Full-field measurement, Image-based methods, Ultra-high speed imaging

Identifiers

Local EPrints ID: 428361
URI: http://eprints.soton.ac.uk/id/eprint/428361
PURE UUID: ef5f5e12-a605-47db-84d5-6073d6447196
ORCID for Fabrice Pierron: ORCID iD orcid.org/0000-0003-2813-4994

Catalogue record

Date deposited: 22 Feb 2019 17:30
Last modified: 20 Jul 2019 00:47

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Contributors

Author: Lloyd Fletcher
Author: Leslie Lamberson
Author: Fabrice Pierron ORCID iD
Editor: J. Kimberley
Editor: L. Lamberson
Editor: S. Mates

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