{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/102767"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/102767","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Methods to improve indentation results on soft materials and anisotropic biological tissues","abstract":"Mechanical properties of soft biological tissues are key to the functionality of such tissues. Indentation has become a leading technique for characterizing the localized mechanical properties of materials, and it is an increasingly popular technique for studying biological materials. This thesis investigates difficulties and challenges regarding the application of micro-scale indentation. This study first develops a novel approach, namely the multi-indent approach (MIA), which mitigates the long-standing challenge of surface detection and broadens the use of instrumented indentation for soft materials. The MIA is experimentally validated on isotropic polyacrylamide gel with load-unload cycles in indentation. Furthermore, it is applied to accurate characterization of poroelastic properties and allows for the use of much smaller probes and indentation depths for all measurements. This study also establishes a corrected method for non-circular contact between a spherical tip and the transversely isotropic material. It develops experimental methods to determine the indentation moduli of a locally transversely isotropic collagenous material as well as the correlation between the aspect ratios (ARs) of contact and correction coefficients for contact areas (RCA). Lastly, this study designs a method for selecting the spherical tip size for indentation based on the collagen fiber distribution in order to correctly sense the differences of local mechanical properties in heterogeneous tissues caused by the uneven fiber distribution. This thesis introduces methods and results that provide guidance and insight regarding the correct design and analysis of indentation experiments on soft materials and anisotropic biological tissues.","abstract_html":"Mechanical properties of soft biological tissues are key to the functionality of such tissues. Indentation has become a leading technique for characterizing the localized mechanical properties of materials, and it is an increasingly popular technique for studying biological materials. This thesis investigates difficulties and challenges regarding the application of micro-scale indentation. This study first develops a novel approach, namely the multi-indent approach (MIA), which mitigates the long-standing challenge of surface detection and broadens the use of instrumented indentation for soft materials. The MIA is experimentally validated on isotropic polyacrylamide gel with load-unload cycles in indentation. Furthermore, it is applied to accurate characterization of poroelastic properties and allows for the use of much smaller probes and indentation depths for all measurements. This study also establishes a corrected method for non-circular contact between a spherical tip and the transversely isotropic material. It develops experimental methods to determine the indentation moduli of a locally transversely isotropic collagenous material as well as the correlation between the aspect ratios (ARs) of contact and correction coefficients for contact areas (RCA). Lastly, this study designs a method for selecting the spherical tip size for indentation based on the collagen fiber distribution in order to correctly sense the differences of local mechanical properties in heterogeneous tissues caused by the uneven fiber distribution. This thesis introduces methods and results that provide guidance and insight regarding the correct design and analysis of indentation experiments on soft materials and anisotropic biological tissues.","abstract_has_math":false,"creators":["Wei, Jie"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Mechanical Engineering","degree_department":null,"school":null,"contributors":["Wagoner Johnson, Amy J.","Insana, Michael","Hu, Yuhang","Dunn, Alison"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2019,"date_issued":"2019-02-07T20:35:49Z","date_published":"2019-02-07T20:35:49Z","updated_at":"2026-07-22T22:24:42Z","subjects":["Indentation","soft material","fiber reinforced"],"languages":["en"],"rights":["Copyright 2018 Jie Wei"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/102767","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Wagoner Johnson, Amy J.","Insana, Michael","Hu, Yuhang","Dunn, Alison"]},{"key":"dc:creator","label":"Author","values":["Wei, Jie"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2019-02-07T20:35:49Z","2021-02-08T10:15:11Z","2018-07-16","2018-12"]},{"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":["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":["Indentation","soft material","fiber reinforced"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2018 Jie Wei"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/102767"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Mechanical properties of soft biological tissues are key to the functionality of such tissues. Indentation has become a leading technique for characterizing the localized mechanical properties of materials, and it is an increasingly popular technique for studying biological materials. This thesis investigates difficulties and challenges regarding the application of micro-scale indentation. This study first develops a novel approach, namely the multi-indent approach (MIA), which mitigates the long-standing challenge of surface detection and broadens the use of instrumented indentation for soft materials. The MIA is experimentally validated on isotropic polyacrylamide gel with load-unload cycles in indentation. Furthermore, it is applied to accurate characterization of poroelastic properties and allows for the use of much smaller probes and indentation depths for all measurements. This study also establishes a corrected method for non-circular contact between a spherical tip and the transversely isotropic material. It develops experimental methods to determine the indentation moduli of a locally transversely isotropic collagenous material as well as the correlation between the aspect ratios (ARs) of contact and correction coefficients for contact areas (RCA). Lastly, this study designs a method for selecting the spherical tip size for indentation based on the collagen fiber distribution in order to correctly sense the differences of local mechanical properties in heterogeneous tissues caused by the uneven fiber distribution. 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It develops experimental methods to determine the indentation moduli of a locally transversely isotropic collagenous material as well as the correlation between the aspect ratios (ARs) of contact and correction coefficients for contact areas (RCA). Lastly, this study designs a method for selecting the spherical tip size for indentation based on the collagen fiber distribution in order to correctly sense the differences of local mechanical properties in heterogeneous tissues caused by the uneven fiber distribution. This thesis introduces methods and results that provide guidance and insight regarding the correct design and analysis of indentation experiments on soft materials and anisotropic biological tissues.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2020-12-01","The student, Jie Wei, accepted the attached license on 2018-07-12 at 15:28.","The student, Jie Wei, submitted this Dissertation for approval on 2018-07-12 at 15:36.","This Dissertation was approved for publication on 2018-07-16 at 13:23.","DSpace SAF Submission Ingestion Package generated from Vireo submission #12852 on 2019-02-07 at 14:15:55","Made available in DSpace on 2019-02-07T20:35:49Z (GMT). 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