Finite element and analytical modelling of roughness induced fatigue crack closure
Finite element and analytical modelling of roughness induced fatigue crack closure
The incidence of roughness induced fatigue crack closure has been studied by finite element and analytical modelling. Results of the finite element model under constant amplitude show: (1) an increasing effect of crack deflection angle on crack closure levels, consistent with the simple geometrical model of Suresh and Ritchie, and (2) little dependence of crack closure levels on the value of the ratio of asperity size to the crack tip plastic zone above a certain critical value. From the finite element model results an important new mechanism to explain the origin of roughness induced crack closure has been proposed, arising from the residual shear deformation of the asperities. This new mechanism has been considered in relation to the conventional description of roughness induced crack closure, in which a global shear offset of the fracture surfaces is required. In particular, problems with the conventional roughness induced crack closure mechanism have been discussed.
An analytical model based on the proposed closure mechanism has been constructed using standard fracture mechanics expressions. The results of the analytical model are shown to be consistent with the finite element results. The model is considered particularly valuable in: (1) showing that the novel micromechanistic understanding derived from the finite element modelling is consistent with well established fracture mechanics descriptions of crack behaviour, and (2) providing a simple analytical description of RICC, without introducing any arbitrary crack shear parameters. The model has been shown to be consistent with the experimental crack closure behaviour typically exhibited by damage tolerant aluminium aerospace alloys.
University of Southampton
Parry, Matthew Roger
df8c0aca-0b3d-4afd-9224-9fb5ac062ed8
2001
Parry, Matthew Roger
df8c0aca-0b3d-4afd-9224-9fb5ac062ed8
Parry, Matthew Roger
(2001)
Finite element and analytical modelling of roughness induced fatigue crack closure.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The incidence of roughness induced fatigue crack closure has been studied by finite element and analytical modelling. Results of the finite element model under constant amplitude show: (1) an increasing effect of crack deflection angle on crack closure levels, consistent with the simple geometrical model of Suresh and Ritchie, and (2) little dependence of crack closure levels on the value of the ratio of asperity size to the crack tip plastic zone above a certain critical value. From the finite element model results an important new mechanism to explain the origin of roughness induced crack closure has been proposed, arising from the residual shear deformation of the asperities. This new mechanism has been considered in relation to the conventional description of roughness induced crack closure, in which a global shear offset of the fracture surfaces is required. In particular, problems with the conventional roughness induced crack closure mechanism have been discussed.
An analytical model based on the proposed closure mechanism has been constructed using standard fracture mechanics expressions. The results of the analytical model are shown to be consistent with the finite element results. The model is considered particularly valuable in: (1) showing that the novel micromechanistic understanding derived from the finite element modelling is consistent with well established fracture mechanics descriptions of crack behaviour, and (2) providing a simple analytical description of RICC, without introducing any arbitrary crack shear parameters. The model has been shown to be consistent with the experimental crack closure behaviour typically exhibited by damage tolerant aluminium aerospace alloys.
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Published date: 2001
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Local EPrints ID: 464343
URI: http://eprints.soton.ac.uk/id/eprint/464343
PURE UUID: 0fc2518e-deeb-489d-a819-036b947e17da
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Date deposited: 04 Jul 2022 22:18
Last modified: 16 Mar 2024 19:26
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Author:
Matthew Roger Parry
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