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Title: Material characterisation and finite element modelling of the cyclic plasticity behaviour of steels
Author: Lu , Jiawa
ISNI:       0000 0004 6351 4092
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2016
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The aim of the study was to experimentally investigate the cyclic plasticity behaviour of steels, and to simulate low cycle fatigue failure by using two material models on either mesoscale or microscale. UMAT subroutines were developed to allow the cyclic plasticity behaviour to be predicted in the ABAQUS FE software. The fatigue behaviour of a P91 power plant steel at a temperature of 600 °C was studied by performing uniaxial fatigue tests and microstructural analysis using electron microscopy. A continuum damage mechanics approach was coupled to the constitutive equations of the Chaboche elasto-visco-plastic model to describe the low cycle fatigue failure at high temperature. A stress partition method was developed to interpret the cyclic softening behaviour, and used to give an initial estimate of the material constants in the Chaboche model. Low cycle fatigue tests were also carried out for a 304 stainless steel at room temperature. The crystal plasticity finite element method was used to predict the hysteresis loops under cyclic loadings for a single crystal or polycrystals. A series of experimental characterisations, including SEM, TEM, and XRD, were conducted to facilitate the understanding of the mechanisms responsible for the mechanical responses, and to determine part of the material constants required in the multi-scale constitutive equations for FE simulation. This method can be used to predict the crack initiation sites based on the local accumulated plastic deformation and local plastic dissipation energy criterion, but it has limitation in predicting the crack initiation caused by precipitates.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available