{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/29530"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/29530","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Fatigue crack growth (FCG) modeling in the presence of nano-obstacles","abstract":"A combination of molecular dynamics and dislocation dynamics simulations is performed to model fatigue crack growth (FCG) in a nano-twinned nickel single crystal. Molecular dynamics simulations are employed to investigate the irreversible interaction of crack-tip emitted dislocations with nano-twins in the vicinity of the crack upon cyclic loading. A method is developed to quantify the irreversibility of slip, and calculate it as a function of the twin lamella thickness and crack-tip to twin lamella spacing. Subsequently, atomistically calculated slip irreversibility is utilized in dislocation dynamics crack growth simulations to understand the role of thickness of the nano-twins as well as the crack-tip to twin spacing on da/dN. In molecular dynamics simulations, in order to study the cyclic slip-twin interactions, the nano-twinned single grain specimen is set up such that it favors two separate cases comprising pure screw and pure edge dislocation nucleation from the crack-tip. Both screw and edge dislocations demonstrate a cyclic steady-state interaction mechanism with the nano-twin under strain control loading. The da/dN formulations, based on discrete dislocation dynamics, are derived for the cases ranging from single to multiple screw or edge dislocations emission from the crack-tip over cycles. The molecular dynamics slip irreversibility is incorporated into the dislocation dynamics based da/dN calculations. An implementation of these formulations demonstrates that both for the cases of decreasing nano- twin thickness or lowering of crack-tip to twin spacing, da/dN also decreases complying with some recent experimental findings in literature.","abstract_html":"A combination of molecular dynamics and dislocation dynamics simulations is performed to model fatigue crack growth (FCG) in a nano-twinned nickel single crystal. Molecular dynamics simulations are employed to investigate the irreversible interaction of crack-tip emitted dislocations with nano-twins in the vicinity of the crack upon cyclic loading. A method is developed to quantify the irreversibility of slip, and calculate it as a function of the twin lamella thickness and crack-tip to twin lamella spacing. Subsequently, atomistically calculated slip irreversibility is utilized in dislocation dynamics crack growth simulations to understand the role of thickness of the nano-twins as well as the crack-tip to twin spacing on da/dN. In molecular dynamics simulations, in order to study the cyclic slip-twin interactions, the nano-twinned single grain specimen is set up such that it favors two separate cases comprising pure screw and pure edge dislocation nucleation from the crack-tip. Both screw and edge dislocations demonstrate a cyclic steady-state interaction mechanism with the nano-twin under strain control loading. The da/dN formulations, based on discrete dislocation dynamics, are derived for the cases ranging from single to multiple screw or edge dislocations emission from the crack-tip over cycles. The molecular dynamics slip irreversibility is incorporated into the dislocation dynamics based da/dN calculations. An implementation of these formulations demonstrates that both for the cases of decreasing nano- twin thickness or lowering of crack-tip to twin spacing, da/dN also decreases complying with some recent experimental findings in literature.","abstract_has_math":false,"creators":["Chowdhury, Piyas"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Mechanical Engineering","degree_department":null,"school":null,"contributors":["Sehitoglu, Huseyin"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2012,"date_issued":"2012-02-01T00:54:12Z","date_published":"2012-02-01T00:54:12Z","updated_at":"2026-07-22T22:25:27Z","subjects":["slip irreversibility","twin","Fatigue crack growth","nano-obstacle","molecular dynamics"],"languages":["en"],"rights":["Copyright 2011 Piyas Chowdhury"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/29530","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Sehitoglu, Huseyin"]},{"key":"dc:creator","label":"Author","values":["Chowdhury, Piyas"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2012-02-01T00:54:12Z","2014-02-01T11:00:22Z","2011-12"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation / Thesis","text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Mechanical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["slip irreversibility","twin","Fatigue crack growth","nano-obstacle","molecular dynamics"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2011 Piyas Chowdhury"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/29530"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["A combination of molecular dynamics and dislocation dynamics simulations is performed to model fatigue crack growth (FCG) in a nano-twinned nickel single crystal. Molecular dynamics simulations are employed to investigate the irreversible interaction of crack-tip emitted dislocations with nano-twins in the vicinity of the crack upon cyclic loading. A method is developed to quantify the irreversibility of slip, and calculate it as a function of the twin lamella thickness and crack-tip to twin lamella spacing. Subsequently, atomistically calculated slip irreversibility is utilized in dislocation dynamics crack growth simulations to understand the role of thickness of the nano-twins as well as the crack-tip to twin spacing on da/dN. In molecular dynamics simulations, in order to study the cyclic slip-twin interactions, the nano-twinned single grain specimen is set up such that it favors two separate cases comprising pure screw and pure edge dislocation nucleation from the crack-tip. Both screw and edge dislocations demonstrate a cyclic steady-state interaction mechanism with the nano-twin under strain control loading. The da/dN formulations, based on discrete dislocation dynamics, are derived for the cases ranging from single to multiple screw or edge dislocations emission from the crack-tip over cycles. The molecular dynamics slip irreversibility is incorporated into the dislocation dynamics based da/dN calculations. An implementation of these formulations demonstrates that both for the cases of decreasing nano- twin thickness or lowering of crack-tip to twin spacing, da/dN also decreases complying with some recent experimental findings in literature.","Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2011-12-08T14:39:34Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 2 Chowdhury_Piyas.doc: 22433792 bytes, checksum: 3ab2921e542073155e9a04a3c5a9cb98 (MD5) Chowdhury_Piyas.pdf: 3304547 bytes, checksum: 02b569aa07b9e6a1c3aab2221a4d1186 (MD5)","Made available in DSpace on 2012-02-01T00:54:12Z (GMT). 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Molecular dynamics simulations are employed to investigate the irreversible interaction of crack-tip emitted dislocations with nano-twins in the vicinity of the crack upon cyclic loading. A method is developed to quantify the irreversibility of slip, and calculate it as a function of the twin lamella thickness and crack-tip to twin lamella spacing. Subsequently, atomistically calculated slip irreversibility is utilized in dislocation dynamics crack growth simulations to understand the role of thickness of the nano-twins as well as the crack-tip to twin spacing on da/dN. In molecular dynamics simulations, in order to study the cyclic slip-twin interactions, the nano-twinned single grain specimen is set up such that it favors two separate cases comprising pure screw and pure edge dislocation nucleation from the crack-tip. Both screw and edge dislocations demonstrate a cyclic steady-state interaction mechanism with the nano-twin under strain control loading. The da/dN formulations, based on discrete dislocation dynamics, are derived for the cases ranging from single to multiple screw or edge dislocations emission from the crack-tip over cycles. The molecular dynamics slip irreversibility is incorporated into the dislocation dynamics based da/dN calculations. An implementation of these formulations demonstrates that both for the cases of decreasing nano- twin thickness or lowering of crack-tip to twin spacing, da/dN also decreases complying with some recent experimental findings in literature.","Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2011-12-08T14:39:34Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 2 Chowdhury_Piyas.doc: 22433792 bytes, checksum: 3ab2921e542073155e9a04a3c5a9cb98 (MD5) Chowdhury_Piyas.pdf: 3304547 bytes, checksum: 02b569aa07b9e6a1c3aab2221a4d1186 (MD5)","Made available in DSpace on 2012-02-01T00:54:12Z (GMT). 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