{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/83968"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/83968","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"The Effect of Stress State and Precipitation on Stress-Induced Martensitic Transformations in Polycrystalline and Single Crystal Shape Memory Alloys: Experiments and Micro-Mechanical Modeling","abstract":"To properly understand stress-induced transformations in aged NiTi single crystals, a micro-mechanical model is used to quantify the stress fields outside perfectly coherent Ti$\\sb{11}$Ni$\\sb{14}$ precipitates in NiTi. Using the model, the decrease in the orientation dependence of $\\sigma\\sb{\\rm cr}$ is linked to the unique orientation relationship that exists between the coherent precipitates in NiTi and the martensite correspondence variant pairs. As experimentally observed the model predicts that peak aged NiTi single crystals loaded under tension along the (100) orientation will show a dramatic decrease in $\\sigma\\sb{\\rm cr}$ while those loaded along (111) will show less of a decrease in $\\sigma\\sb{\\rm cr}.$ The effect of different aging treatments is properly explained by extending the local stress field model to the case of semi-coherent precipitates. In addition, the depletion of Ni in the matrix surrounding the precipitates is found to contribute to changes in $\\sigma\\sb{\\rm cr}$ and M$\\sb{\\rm s}$ for aged NiTi alloys.","abstract_html":"To properly understand stress-induced transformations in aged NiTi single crystals, a micro-mechanical model is used to quantify the stress fields outside perfectly coherent Ti$\\sb{11}$Ni$\\sb{14}$ precipitates in NiTi. Using the model, the decrease in the orientation dependence of <span class=\"etd-inline-math\">&sigma;\\sb{\\rm cr}</span> is linked to the unique orientation relationship that exists between the coherent precipitates in NiTi and the martensite correspondence variant pairs. As experimentally observed the model predicts that peak aged NiTi single crystals loaded under tension along the (100) orientation will show a dramatic decrease in <span class=\"etd-inline-math\">&sigma;\\sb{\\rm cr}</span> while those loaded along (111) will show less of a decrease in <span class=\"etd-inline-math\">&sigma;\\sb{\\rm cr}.</span> The effect of different aging treatments is properly explained by extending the local stress field model to the case of semi-coherent precipitates. In addition, the depletion of Ni in the matrix surrounding the precipitates is found to contribute to changes in <span class=\"etd-inline-math\">&sigma;\\sb{\\rm cr}</span> and M$\\sb{\\rm s}$ for aged NiTi alloys.","abstract_has_math":true,"creators":["Gall, Kenneth Allen"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Mechanical Engineering","degree_department":null,"school":null,"contributors":["Sehitoglu, Huseyin"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-09-25T21:12:57Z","date_published":"2015-09-25T21:12:57Z","updated_at":"2026-07-22T22:26:22Z","subjects":["Engineering, Metallurgy"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(MiAaPQ)AAI9904460"],"render_values":[{"text":"(MiAaPQ)AAI9904460","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/83968","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":["Gall, Kenneth Allen"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-09-25T21:12:57Z","10000-01-01","1998"]},{"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":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"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":["Engineering, Metallurgy"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/83968","(MiAaPQ)AAI9904460"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["To properly understand stress-induced transformations in aged NiTi single crystals, a micro-mechanical model is used to quantify the stress fields outside perfectly coherent Ti$\\sb{11}$Ni$\\sb{14}$ precipitates in NiTi. Using the model, the decrease in the orientation dependence of $\\sigma\\sb{\\rm cr}$ is linked to the unique orientation relationship that exists between the coherent precipitates in NiTi and the martensite correspondence variant pairs. As experimentally observed the model predicts that peak aged NiTi single crystals loaded under tension along the (100) orientation will show a dramatic decrease in $\\sigma\\sb{\\rm cr}$ while those loaded along (111) will show less of a decrease in $\\sigma\\sb{\\rm cr}.$ The effect of different aging treatments is properly explained by extending the local stress field model to the case of semi-coherent precipitates. In addition, the depletion of Ni in the matrix surrounding the precipitates is found to contribute to changes in $\\sigma\\sb{\\rm cr}$ and M$\\sb{\\rm s}$ for aged NiTi alloys.","Made available in DSpace on 2015-09-25T21:12:57Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 9904460.pdf: 12843380 bytes, checksum: daca48e1875010126280ae2265214005 (MD5) Previous issue date: 1998","Embargo set by: Seth Robbins for item 85249 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","268 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1998."]},{"key":"dc:title","label":"Title","values":["The Effect of Stress State and Precipitation on Stress-Induced Martensitic Transformations in Polycrystalline and Single Crystal Shape Memory Alloys: Experiments and Micro-Mechanical Modeling"]}]}],"canonical_facts":{"dc:contributor":["Sehitoglu, Huseyin"],"dc:creator":["Gall, Kenneth Allen"],"dc:date":["2015-09-25T21:12:57Z","10000-01-01","1998"],"dc:description":["To properly understand stress-induced transformations in aged NiTi single crystals, a micro-mechanical model is used to quantify the stress fields outside perfectly coherent Ti$\\sb{11}$Ni$\\sb{14}$ precipitates in NiTi. Using the model, the decrease in the orientation dependence of $\\sigma\\sb{\\rm cr}$ is linked to the unique orientation relationship that exists between the coherent precipitates in NiTi and the martensite correspondence variant pairs. As experimentally observed the model predicts that peak aged NiTi single crystals loaded under tension along the (100) orientation will show a dramatic decrease in $\\sigma\\sb{\\rm cr}$ while those loaded along (111) will show less of a decrease in $\\sigma\\sb{\\rm cr}.$ The effect of different aging treatments is properly explained by extending the local stress field model to the case of semi-coherent precipitates. In addition, the depletion of Ni in the matrix surrounding the precipitates is found to contribute to changes in $\\sigma\\sb{\\rm cr}$ and M$\\sb{\\rm s}$ for aged NiTi alloys.","Made available in DSpace on 2015-09-25T21:12:57Z (GMT). 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