{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/106396"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/106396","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"The fatigue crack growth behavior of superelastic nickel titanium","abstract":"Understanding of fatigue crack growth phenomena in shape memory alloys under superelastic conditions continues to elude the scientific community: The stress induced martensite phase causes deviations of stress intensity and state at the tip from the classical handbook solutions widely relied on for crack growth characterization. In this work, novel methods of stress intensity factor extraction based on in situ and ex situ Digital Image Correlation are implemented to characterize the effective fatigue damage tolerance of NiTi single crystals under superelastic conditions. It is found that, due to crack tip stress induced martensite transformation, NiTi exhibits shielding (reduction from theoretical stress intensity factor calculations) of about 30\\% on average. The stress intensity reduction levels from the superelastic austenite, stable martensite and stable austenite are also compared. It is found that the stable austenite-martensite crystal structures exhibit almost identical K reduction, attributed to plastic flow, while the superelastic austenite structure, exhibiting higher reduction levels, demonstrates the shielding effect of the stress induced transformation.","abstract_html":"Understanding of fatigue crack growth phenomena in shape memory alloys under superelastic conditions continues to elude the scientific community: The stress induced martensite phase causes deviations of stress intensity and state at the tip from the classical handbook solutions widely relied on for crack growth characterization. In this work, novel methods of stress intensity factor extraction based on in situ and ex situ Digital Image Correlation are implemented to characterize the effective fatigue damage tolerance of NiTi single crystals under superelastic conditions. It is found that, due to crack tip stress induced martensite transformation, NiTi exhibits shielding (reduction from theoretical stress intensity factor calculations) of about 30\\% on average. The stress intensity reduction levels from the superelastic austenite, stable martensite and stable austenite are also compared. It is found that the stable austenite-martensite crystal structures exhibit almost identical K reduction, attributed to plastic flow, while the superelastic austenite structure, exhibiting higher reduction levels, demonstrates the shielding effect of the stress induced transformation.","abstract_has_math":false,"creators":["Yaacoub, Jad"],"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":2020,"date_issued":"2020-03-02T22:18:19Z","date_published":"2020-03-02T22:18:19Z","updated_at":"2026-07-22T22:24:47Z","subjects":["Shape Memory Alloy","NiTi","Fatigue Crack Growth","Superelasticity"],"languages":["en"],"rights":["Copyright 2019 Jad Yaacoub"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/106396","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":["Yaacoub, Jad"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2020-03-02T22:18:19Z","2022-03-03T10:15:27Z","2019-12-12","2019-12"]},{"key":"dc:type","label":"Dc Type","values":["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":["Shape Memory Alloy","NiTi","Fatigue Crack Growth","Superelasticity"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2019 Jad Yaacoub"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/106396"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Understanding of fatigue crack growth phenomena in shape memory alloys under superelastic conditions continues to elude the scientific community: The stress induced martensite phase causes deviations of stress intensity and state at the tip from the classical handbook solutions widely relied on for crack growth characterization. In this work, novel methods of stress intensity factor extraction based on in situ and ex situ Digital Image Correlation are implemented to characterize the effective fatigue damage tolerance of NiTi single crystals under superelastic conditions. It is found that, due to crack tip stress induced martensite transformation, NiTi exhibits shielding (reduction from theoretical stress intensity factor calculations) of about 30\\% on average. The stress intensity reduction levels from the superelastic austenite, stable martensite and stable austenite are also compared. It is found that the stable austenite-martensite crystal structures exhibit almost identical K reduction, attributed to plastic flow, while the superelastic austenite structure, exhibiting higher reduction levels, demonstrates the shielding effect of the stress induced transformation.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2021-12-01","The student, Jad Yaacoub, accepted the attached license on 2019-12-11 at 12:19.","The student, Jad Yaacoub, submitted this Thesis for approval on 2019-12-11 at 12:23.","This Thesis was approved for publication on 2019-12-12 at 09:19.","DSpace SAF Submission Ingestion Package generated from Vireo submission #14789 on 2020-02-28 at 17:24:23","Made available in DSpace on 2020-03-02T22:18:19Z (GMT). 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In this work, novel methods of stress intensity factor extraction based on in situ and ex situ Digital Image Correlation are implemented to characterize the effective fatigue damage tolerance of NiTi single crystals under superelastic conditions. It is found that, due to crack tip stress induced martensite transformation, NiTi exhibits shielding (reduction from theoretical stress intensity factor calculations) of about 30\\% on average. The stress intensity reduction levels from the superelastic austenite, stable martensite and stable austenite are also compared. It is found that the stable austenite-martensite crystal structures exhibit almost identical K reduction, attributed to plastic flow, while the superelastic austenite structure, exhibiting higher reduction levels, demonstrates the shielding effect of the stress induced transformation.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2021-12-01","The student, Jad Yaacoub, accepted the attached license on 2019-12-11 at 12:19.","The student, Jad Yaacoub, submitted this Thesis for approval on 2019-12-11 at 12:23.","This Thesis was approved for publication on 2019-12-12 at 09:19.","DSpace SAF Submission Ingestion Package generated from Vireo submission #14789 on 2020-02-28 at 17:24:23","Made available in DSpace on 2020-03-02T22:18:19Z (GMT). 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