Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for subject:(XCZM). Showing records 1 – 2 of 2 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


University of Manchester

1. Crump, Timothy. Modelling dynamic cracking of graphite.

Degree: 2017, University of Manchester

Advances in dynamic fracture modelling have become more frequent due to increases in computer speed, meaning that its application to industrial problems has become viable. From this, the author has reviewed current literature in terms of graphite material properties, structural dynamics, fracture mechanics and modelling methodologies to be able to address operational issues related to the ageing of Advanced Gas-cooled Reactor (AGR) cores. In particular, the experimentally observed Prompt Secondary Cracking (PSC) of graphite moderator bricks which has yet to be observed within operational reactors, with the objective of supporting their plant life extension. A method known as eXtended Finite Element Method with Cohesive Zones (XCZM) was developed within Code_Aster open-source FEM software. This enabled the incorporation of velocity toughening, irradiation-induced material degradation effects and multiple 3D dynamic crack initiations, propagations and arrests into a single model, which covers the major known attributes of the PSC mechanism. Whilst developing XCZM, several publications were produced. This started with first demonstrating XCZM's ability to model the PSC mechanism in 2D and consequently that methane holes have a noticeable effect on crack propagation speeds. Following on from this, XCZM was benchmarked in 2D against literature experiments and available model data which consequently highlighted that velocity toughening was an integral feature in producing energetically correct fracture speeds. Leading on from this, XCZM was taken into 3D and demonstrated that it produced experimentally observed bifurcation angle from a literature example. This meant that when a 3D graphite brick was modelled that the crack profile was equivalent to an accepted quasi-static profile. As a consequence of this validation, the XCZM approach was able to model PSC and give insight into features that could not be investigated previously including: finer-scale heterogeneous effects on a dynamic crack profile, comparison between Primary and Secondary crack profiles and also, 3D crack interaction with a methane hole, including insight into possible crack arrest. XCZM was shown to improve upon previous 2D models of experiments that showed the plausibility of PSC; this was achieved by eliminating the need for user intervention and also incorporation of irradiation damage effects through User-defined Material properties (UMAT). Finally, while applying XCZM to a full-scale 3D graphite brick including reactor effects, it was shown that PSC is likely to occur under LEFM assumptions and that the Secondary crack initiates before the Primary crack arrests axially meaning that modal analysis would not be able to fully model PSC. Advisors/Committee Members: JIVKOV, ANDREY AP, Mummery, Paul, Jivkov, Andrey.

Subjects/Keywords: graphite; dynamic fracture; XFEM; Cohesive zone; Nuclear; XCZM; Structural integrity; meso; Prompt Secondary Cracking; AGR

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Crump, T. (2017). Modelling dynamic cracking of graphite. (Doctoral Dissertation). University of Manchester. Retrieved from http://www.manchester.ac.uk/escholar/uk-ac-man-scw:312603

Chicago Manual of Style (16th Edition):

Crump, Timothy. “Modelling dynamic cracking of graphite.” 2017. Doctoral Dissertation, University of Manchester. Accessed October 18, 2019. http://www.manchester.ac.uk/escholar/uk-ac-man-scw:312603.

MLA Handbook (7th Edition):

Crump, Timothy. “Modelling dynamic cracking of graphite.” 2017. Web. 18 Oct 2019.

Vancouver:

Crump T. Modelling dynamic cracking of graphite. [Internet] [Doctoral dissertation]. University of Manchester; 2017. [cited 2019 Oct 18]. Available from: http://www.manchester.ac.uk/escholar/uk-ac-man-scw:312603.

Council of Science Editors:

Crump T. Modelling dynamic cracking of graphite. [Doctoral Dissertation]. University of Manchester; 2017. Available from: http://www.manchester.ac.uk/escholar/uk-ac-man-scw:312603


University of Manchester

2. Crump, Timothy. Modelling dynamic cracking of graphite.

Degree: Thesis (Eng.D.), 2018, University of Manchester

Advances in dynamic fracture modelling have become more frequent due to increases in computer speed, meaning that its application to industrial problems has become viable. From this, the author has reviewed current literature in terms of graphite material properties, structural dynamics, fracture mechanics and modelling methodologies to be able to address operational issues related to the ageing of Advanced Gas-cooled Reactor (AGR) cores. In particular, the experimentally observed Prompt Secondary Cracking (PSC) of graphite moderator bricks which has yet to be observed within operational reactors, with the objective of supporting their plant life extension. A method known as eXtended Finite Element Method with Cohesive Zones (XCZM) was developed within Code_Aster open-source FEM software. This enabled the incorporation of velocity toughening, irradiation-induced material degradation effects and multiple 3D dynamic crack initiations, propagations and arrests into a single model, which covers the major known attributes of the PSC mechanism. Whilst developing XCZM, several publications were produced. This started with first demonstrating XCZM's ability to model the PSC mechanism in 2D and consequently that methane holes have a noticeable effect on crack propagation speeds. Following on from this, XCZM was benchmarked in 2D against literature experiments and available model data which consequently highlighted that velocity toughening was an integral feature in producing energetically correct fracture speeds. Leading on from this, XCZM was taken into 3D and demonstrated that it produced experimentally observed bifurcation angle from a literature example. This meant that when a 3D graphite brick was modelled that the crack profile was equivalent to an accepted quasi-static profile. As a consequence of this validation, the XCZM approach was able to model PSC and give insight into features that could not be investigated previously including: finer-scale heterogeneous effects on a dynamic crack profile, comparison between Primary and Secondary crack profiles and also, 3D crack interaction with a methane hole, including insight into possible crack arrest. XCZM was shown to improve upon previous 2D models of experiments that showed the plausibility of PSC; this was achieved by eliminating the need for user intervention and also incorporation of irradiation damage effects through User-defined Material properties (UMAT). Finally, while applying XCZM to a full-scale 3D graphite brick including reactor effects, it was shown that PSC is likely to occur under LEFM assumptions and that the Secondary crack initiates before the Primary crack arrests axially meaning that modal analysis would not be able to fully model PSC.

Subjects/Keywords: Structural integrity; AGR; Prompt Secondary Cracking; meso; XCZM; graphite; Cohesive zone; XFEM; dynamic fracture; Nuclear

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Crump, T. (2018). Modelling dynamic cracking of graphite. (Doctoral Dissertation). University of Manchester. Retrieved from https://www.research.manchester.ac.uk/portal/en/theses/modelling-dynamic-cracking-of-graphite(71e81d6f-e712-458c-aa48-0a256749258a).html ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.764610

Chicago Manual of Style (16th Edition):

Crump, Timothy. “Modelling dynamic cracking of graphite.” 2018. Doctoral Dissertation, University of Manchester. Accessed October 18, 2019. https://www.research.manchester.ac.uk/portal/en/theses/modelling-dynamic-cracking-of-graphite(71e81d6f-e712-458c-aa48-0a256749258a).html ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.764610.

MLA Handbook (7th Edition):

Crump, Timothy. “Modelling dynamic cracking of graphite.” 2018. Web. 18 Oct 2019.

Vancouver:

Crump T. Modelling dynamic cracking of graphite. [Internet] [Doctoral dissertation]. University of Manchester; 2018. [cited 2019 Oct 18]. Available from: https://www.research.manchester.ac.uk/portal/en/theses/modelling-dynamic-cracking-of-graphite(71e81d6f-e712-458c-aa48-0a256749258a).html ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.764610.

Council of Science Editors:

Crump T. Modelling dynamic cracking of graphite. [Doctoral Dissertation]. University of Manchester; 2018. Available from: https://www.research.manchester.ac.uk/portal/en/theses/modelling-dynamic-cracking-of-graphite(71e81d6f-e712-458c-aa48-0a256749258a).html ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.764610

.