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Application of the Theta projection method to creep modelling using Abaqus

Will Harrison Orcid Logo, W.J. Evans

Abaqus UK Regional Users Meeting

Swansea University Author: Will Harrison Orcid Logo

Abstract

The aim of this project was to create a creep model using Abaqus, based on the theta projection method. This method has been shown to accurately predict primary, secondary and tertiary creep behaviour for a range of engineering materials. A constitutive relationship based on the theta projection met...

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Published in: Abaqus UK Regional Users Meeting
Published: 2007
URI: https://cronfa.swan.ac.uk/Record/cronfa29848
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Abstract: The aim of this project was to create a creep model using Abaqus, based on the theta projection method. This method has been shown to accurately predict primary, secondary and tertiary creep behaviour for a range of engineering materials. A constitutive relationship based on the theta projection method was already available, with creep behaviour evolving with the accumulation of state variables based on dislocation hardening, dislocation recovery and internal material damage. An Abaqus based user subroutine for this relationship was compiled which included creep rupture based on a Kachanov type failure process. The model was designed to integrate with a fatigue crack growth model to produce a coupled high temperature fatigue model to compare against experimental data as part of an EPSRC project undertaken within the Rolls Royce UTC at Swansea.The creep model was used to predict the creep behaviour of various tested specimens for the titanium alloy, Ti-6246. Specimen geometries included uniaxial, biaxial, round-circumferentially notched (RCN) and V-shaped circumferentially notched (VCN). Strain rate and creep life predictions were compared to experimental data where available with results showing a good correlation. Also, the stress relaxation around a fatigue crack tip was investigated along with the effect of continuum creep damage on the rate of the advancing fatigue crack. Predictions highlight the importance of the both maximum principle stress and shear stress on the mechanical processes at the crack tip. The model also quantified the increasing effect of creep damage in the later stages of fatigue crack propagation. Verification of this work is ongoing at Swansea University.
Keywords: Creep, Creep Rupture, Damage, Titanium, Notches, Theta Projection Method, Low Cycle Fatigue, Crack Growth
College: College of Engineering