{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/110604"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/110604","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Dual scale porosity effects on crack-defect interactions in additively manufactured Ti-6Al-4V","abstract":"This Thesis was approved for publication on 2021-04-30 at 11:34.","abstract_html":"This Thesis was approved for publication on 2021-04-30 at 11:34.","abstract_has_math":false,"creators":["Muro-Barrios, Raymundo"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Aerospace Engineering","degree_department":null,"school":null,"contributors":["Chew, Huck Beng","Lambros, John"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2021,"date_issued":"2021-09-17T01:13:35Z","date_published":"2021-09-17T01:13:35Z","updated_at":"2026-07-22T22:24:52Z","subjects":["Additive manufacturing","Numerical methods","WARP3D","Ti-6Al-4V","Dual-scale porosity","Modified boundary layer","Void defects","Additive manufacturing defects","Gurson yield criterion","Fracture process Zone","Fracture","Fatigue","Fracture mechanics","Ductile fracture"],"languages":["en"],"rights":["Copyright 2021 Raymundo Muro-Barrios"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/110604","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Chew, Huck Beng","Lambros, John"]},{"key":"dc:creator","label":"Author","values":["Muro-Barrios, Raymundo"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2021-09-17T01:13:35Z","2021-04-30","2021-05"]},{"key":"dc:type","label":"Dc Type","values":["text","Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Aerospace 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":["Additive manufacturing","Numerical methods","WARP3D","Ti-6Al-4V","Dual-scale porosity","Modified boundary layer","Void defects","Additive manufacturing defects","Gurson yield criterion","Fracture process Zone","Fracture","Fatigue","Fracture mechanics","Ductile fracture"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2021 Raymundo Muro-Barrios"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/110604"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["This Thesis was approved for publication on 2021-04-30 at 11:34.","DSpace SAF Submission Ingestion Package generated from Vireo submission #16621 on 2021-09-16 at 16:49:39","Made available in DSpace on 2021-09-17T01:13:35Z (GMT). No. of bitstreams: 2 MURO-BARRIOS-THESIS-2021.pdf: 8738432 bytes, checksum: d5ee3d97ce66ca9235c26ff434f6511d (MD5) LICENSE.txt: 4218 bytes, checksum: 26cc4b585fcc4a2df5ab8e9ec2ac9f76 (MD5) Previous issue date: 2021-04-30","Microstructural defects and unpredictable fracture behavior have limited the widespread use of additively manufactured (AM) alloys in load bearing components. In addition to background pores (2-12 μm) nucleated from particle inclusions responsible for ductile fracture in conventional metals, larger defects (20-50 μm) can be introduced during the additive manufacturing process resulting in a dual-scale porosity failure process in AM alloys. The effect of these AM defects on the fracture behavior of AM Direct Metal Laser Melted Ti-6Al-4V has been previously observed in Scanning Electron Microscopy and Digital Image Correlation analyses, which suggest AM defects lead to the premature failure in fracture and fatigue of AM metals. However, the specific failure mechanisms associated with the AM defects have not been identified. In this thesis, a numerical approach is undertaken to quantitatively elucidate the role of the dual-scale porosity and resulting crack-defect interactions in AM Ti-6Al-4V alloys. A small-scale yielding, modified boundary layer model with imposed monotonically increasing K_I (Stress Intensity Factor) remote displacement loading was used to study crack propagation through a local distribution of dual size-scale voids. The Gurson yield function was implemented to model the background porosity while the larger AM defects were explicitly represented. Micrographs were taken of physical AM Ti-6Al-4V specimen cross-sections to determine the expected size and frequency of AM defects. Fracture resistance curves were generated for random AM void distributions with increasing levels of AM defects. Over and underperforming material samples with off-nominal fracture resistance were analyzed in more detail through observation of 3D void interactions in cross-sectional model images. It is shown that AM defects activate isolated and clustered damage zones ahead of the crack tip, blunt the crack tip, promote crack tortuosity, and at times appear to increase the local material toughness over a conventional alloy. Conversely, planar clusters of AM defects can form preferential crack planes that may be responsible for the premature failure of AM components. Inclusion of the AM defects also generates more opportunities for localized dissipation of plastic work, which suggests the potential for achieving “fracture-by-design” through strategic void placements. Preliminary materials design concepts resulting in significantly improved apparent fracture toughness over conventional alloys are discussed.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2021-09-16 without embargo terms","The student, Raymundo Muro-Barrios, accepted the attached license on 2021-04-30 at 10:15.","The student, Raymundo Muro-Barrios, submitted this Thesis for approval on 2021-04-30 at 10:32."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Dual scale porosity effects on crack-defect interactions in additively manufactured Ti-6Al-4V"]}]}],"canonical_facts":{"dc:contributor":["Chew, Huck Beng","Lambros, John"],"dc:creator":["Muro-Barrios, Raymundo"],"dc:date":["2021-09-17T01:13:35Z","2021-04-30","2021-05"],"dc:description":["This Thesis was approved for publication on 2021-04-30 at 11:34.","DSpace SAF Submission Ingestion Package generated from Vireo submission #16621 on 2021-09-16 at 16:49:39","Made available in DSpace on 2021-09-17T01:13:35Z (GMT). No. of bitstreams: 2 MURO-BARRIOS-THESIS-2021.pdf: 8738432 bytes, checksum: d5ee3d97ce66ca9235c26ff434f6511d (MD5) LICENSE.txt: 4218 bytes, checksum: 26cc4b585fcc4a2df5ab8e9ec2ac9f76 (MD5) Previous issue date: 2021-04-30","Microstructural defects and unpredictable fracture behavior have limited the widespread use of additively manufactured (AM) alloys in load bearing components. In addition to background pores (2-12 μm) nucleated from particle inclusions responsible for ductile fracture in conventional metals, larger defects (20-50 μm) can be introduced during the additive manufacturing process resulting in a dual-scale porosity failure process in AM alloys. The effect of these AM defects on the fracture behavior of AM Direct Metal Laser Melted Ti-6Al-4V has been previously observed in Scanning Electron Microscopy and Digital Image Correlation analyses, which suggest AM defects lead to the premature failure in fracture and fatigue of AM metals. However, the specific failure mechanisms associated with the AM defects have not been identified. In this thesis, a numerical approach is undertaken to quantitatively elucidate the role of the dual-scale porosity and resulting crack-defect interactions in AM Ti-6Al-4V alloys. A small-scale yielding, modified boundary layer model with imposed monotonically increasing K_I (Stress Intensity Factor) remote displacement loading was used to study crack propagation through a local distribution of dual size-scale voids. The Gurson yield function was implemented to model the background porosity while the larger AM defects were explicitly represented. Micrographs were taken of physical AM Ti-6Al-4V specimen cross-sections to determine the expected size and frequency of AM defects. Fracture resistance curves were generated for random AM void distributions with increasing levels of AM defects. Over and underperforming material samples with off-nominal fracture resistance were analyzed in more detail through observation of 3D void interactions in cross-sectional model images. It is shown that AM defects activate isolated and clustered damage zones ahead of the crack tip, blunt the crack tip, promote crack tortuosity, and at times appear to increase the local material toughness over a conventional alloy. Conversely, planar clusters of AM defects can form preferential crack planes that may be responsible for the premature failure of AM components. Inclusion of the AM defects also generates more opportunities for localized dissipation of plastic work, which suggests the potential for achieving “fracture-by-design” through strategic void placements. Preliminary materials design concepts resulting in significantly improved apparent fracture toughness over conventional alloys are discussed.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2021-09-16 without embargo terms","The student, Raymundo Muro-Barrios, accepted the attached license on 2021-04-30 at 10:15.","The student, Raymundo Muro-Barrios, submitted this Thesis for approval on 2021-04-30 at 10:32."],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/110604"],"dc:language":["en"],"dc:rights":["Copyright 2021 Raymundo Muro-Barrios"],"dc:subject":["Additive manufacturing","Numerical methods","WARP3D","Ti-6Al-4V","Dual-scale porosity","Modified boundary layer","Void defects","Additive manufacturing defects","Gurson yield criterion","Fracture process Zone","Fracture","Fatigue","Fracture mechanics","Ductile fracture"],"dc:title":["Dual scale porosity effects on crack-defect interactions in additively manufactured Ti-6Al-4V"],"dc:type":["text","Thesis"],"thesis:degree_discipline":["Aerospace Engineering"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:52Z"}