2026-09-19T14:23:32Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/448122022-01-13T07:54:33Zcom_1721.1_7582com_1721.1_7581col_1721.1_131024
Christopher A. Schuh.
Witmer, Lisa Marie
Massachusetts Institute of Technology. Dept. of Materials Science and Engineering.
Massachusetts Institute of Technology. Department of Materials Science and Engineering
2009-03-16T19:46:43Z
2009-03-16T19:46:43Z
2007
2007
http://hdl.handle.net/1721.1/44812
301349410
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.
Includes bibliographical references (leaves 29-30).
An Iron-based bulk metallic glass was studied using nanoindentation to examine the effects of fatigue on the onset of plasticity. Experiments were performed on samples in an as received and 0.8Tg 12-hour annealed condition. The nanoindentation testing procedure focused on investigating fatigue of these samples through cyclic loading as well as investigating the maximum shear stress induced through varied loading in the as-received sample. With respect to the maximum induced shear stress, no clear correlation between induced stress and the onset of plasticity in this material was observed. The results of fatigue in the as-received sample demonstrate material strengthening upon repeated loading, while the effect is absent in the annealed sample. The results are discussed in relation to material structure and free volume, and analysis suggests that structural relaxation during annealing serves to inhibit material strengthening by fatigue in metallic glasses, while cycling in the as-received sample likely strengthens due to a local effect.
by Lisa Marie Witmer.
S.B.
30 leaves
eng
Massachusetts Institute of Technology
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http://dspace.mit.edu/handle/1721.1/7582
Materials Science and Engineering.
An investigation of fatigue in an Fe-based metallic glass by nanoindentation
Investigation of fatigue in an iron-based metallic glass by nanoindentation
Thesis
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<Abstract>An Iron-based bulk metallic glass was studied using nanoindentation to examine the effects of fatigue on the onset of plasticity. Experiments were performed on samples in an as received and 0.8Tg 12-hour annealed condition. The nanoindentation testing procedure focused on investigating fatigue of these samples through cyclic loading as well as investigating the maximum shear stress induced through varied loading in the as-received sample. With respect to the maximum induced shear stress, no clear correlation between induced stress and the onset of plasticity in this material was observed. The results of fatigue in the as-received sample demonstrate material strengthening upon repeated loading, while the effect is absent in the annealed sample. The results are discussed in relation to material structure and free volume, and analysis suggests that structural relaxation during annealing serves to inhibit material strengthening by fatigue in metallic glasses, while cycling in the as-received sample likely strengthens due to a local effect.</Abstract>
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