2026-09-22T04:13:17Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/106396 2023-07-11 col_2142_5131 col_2142_14787 com_2142_5130 com_2142_9630 com_2142_234

Sehitoglu, Huseyin Yaacoub, Jad 2020-03-02T22:18:19Z 2020-03-02T22:18:19Z 2022-03-03T10:15:27Z 2019-12-12 2019-12 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). No. of bitstreams: 2 YAACOUB-THESIS-2019.pdf: 2451149 bytes, checksum: 5a35849177fe96cfc06ccd876bd57a32 (MD5) LICENSE.txt: 4208 bytes, checksum: 82605b00c707ee7ae29963249ddbe457 (MD5) Previous issue date: 2019-12-12 Embargo set by: Seth Robbins for item 113939 Lift date: 2022-03-02T22:18:25Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system U of I Only Restriction Lifted for Item 113939 on 2022-03-03T10:15:27Z. application/pdf http://hdl.handle.net/2142/106396 en Copyright 2019 Jad Yaacoub Shape Memory Alloy NiTi Fatigue Crack Growth Superelasticity The fatigue crack growth behavior of superelastic nickel titanium text text Mechanical Sci & Engineering Mechanical Engineering University of Illinois at Urbana-Champaign Thesis M.S.