Session: MF-05-01 Fitness-For-Service and Failure Assessment-1

Paper Number: 122348

122348 - Application of Crystal Plasticity Finite Element in Updating Industrial Integrity Assessment Practices. 

High temperature power plants require an extensive knowledge of the materials behaviour used to assess the safety critical components. Currently, the design and assessment codes used to ensure each component is fit for purpose rely on extensive experimental data of deformation and damage. This reliance on extensive experimental studies is expensive, time consuming, and often does not cover the full range of conditions a service component may experience resulting in over-conservatism. One method for improving code predictions involves utilizing modelling methods to fill in the gaps left by experimental programs. However, such models must be as trustworthy as experiments and represent the relevant physics. Numerous studies have shown that mesoscale interaction between the material’s constituents and their associated variability that a substantial effect on deformation leading to damage thus, must be incorporated into any model if they are to be used in conjunction with experiments to update codes and standards. Crystal plasticity finite element (CPFE) has been shown to efficiently incorporate mesoscale behaviour in materials deformation. However, it is not practical to model entire components using this method due to the high computational cost. To be able to fully utilize CPFE at the component scale, other numerical techniques are required, such as sub-modelling.

Within this work the British R5 procedure for estimating the life of a component at high temperature under fatigue-dwell loading is utilized and, compared with RCC-MRx and ASME-III. Within these documents, localized regions of high stress are investigated using stress linearization over stress classification lines. They advise that, if necessary, the conservatism of elastic analysis can be reduced via inelastic analysis so this work proposes a new inelastic analysis method which involves the application of crystal plasticity to localized regions of interest determined by stress categorization lines. To show the potential of utilizing CPFE for inelastic analysis, a weld will be investigated in this case study due to the significant role microstructure plays in these joins. This will be performed by using the sub-modelling feature of Abaqus to extract the boundary conditions from an area of interest, such as an area containing a high stress concentration, and apply these to progressively smaller model geometries, culminating with a crystal plasticity model using a representative volume element (RVE). To introduce the variability experienced at the mesoscale, the same boundary conditions are applied to many different RVEs. This variability allows for uncertainty quantification and so provides a means of systematically exhibiting confidence in the information provided. This process allows for localized areas that are expected to be regions in which failure occurs to directly consider microstructure through crystal plasticity modelling, potentially  enabling significant improvements in material behaviour predictions.

Presenting Author: Edward Horton University of Bristol

Presenting Author Biography: Edward Horton is a PhD student at the University of Bristol. His main research focus is validating and developing crystal plasticity models for austenitic stainless steels for use within industrial standards.

Authors:

Edward Horton University of Bristol
Mahmoud Mostafavi University of Bristol
David Knowles University of Bristol
Marc Chevalier EDF Energy