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Title: Prediction of crack growth in a nickel-based superalloy under fatigue-oxidation conditions
Authors: Zhao, Liguo
Tong, Jie
Hardy, M.C.
Keywords: Finite element analysis
Oxygen diffusion
Accumulated inelastic strain
Failure envelop
Crack growth rate
Nickel-based alloys
Issue Date: 2010
Publisher: © Elsevier
Citation: ZHAO, L., TONG, J. and HARDY, M.C., 2010. Prediction of crack growth in a nickel-based superalloy under fatigue-oxidation conditions. Engineering Fracture Mechanics, 77 (6), pp.925-938.
Abstract: Prediction of oxidation-assisted crack growth has been carried out for a nickel-based superalloy at elevated temperature based on finite element analyses of oxygen diffusion, coupled with viscoplastic deformation, near a fatigue crack tip. The material constitutive behaviour, implemented in the finite element code ABAQUS via a user-defined material subroutine (UMAT), was described by a unified viscoplastic model with non-linear kinematic and isotropic hardening rules. Diffusion of oxygen was assumed to be controlled by two parameters, the oxygen diffusivity and deformation-assisted oxygen mobility. Low frequencies and superimposed hold periods at peak loads significantly enhanced oxygen concentration near the crack tip. Evaluations of near-tip deformation and oxygen concentration were performed, which led to the construction of a failure envelop for crack growth based on the consideration of both oxygen concentration and accumulated inelastic strain near the crack tip. The failure envelop was then utilised to predict crack growth rates in a compact tension (CT) specimen under fatigue-oxidation conditions for selected loading ranges, frequencies and dwell periods. The predictions from the fatigue-oxidation failure envelop compared well with the experimental results for triangular and dwell loading waveforms, with marked improvements achieved over those predicted from the viscoplastic model alone. The fatigue-oxidation predictions also agree well with the experimental results for slow-fast loading waveforms, but not for fast-slow waveforms where the effect of oxidation is much reduced.
Description: This is the author’s version of a work that was accepted for publication in the journal Engineering Fracture Mechanics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published at: http://dx.doi.org/10.1016/j.engfracmech.2010.02.005
Version: Accepted for publication
DOI: 10.1016/j.engfracmech.2010.02.005
URI: https://dspace.lboro.ac.uk/2134/10908
Publisher Link: http://dx.doi.org/10.1016/j.engfracmech.2010.02.005
Appears in Collections:Published Articles (Mechanical, Electrical and Manufacturing Engineering)

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