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Ali S. Argon. Demkowicz, Michael J. (Michael John), 1977- Massachusetts Institute of Technology. Dept. of Mechanical Engineering. Massachusetts Institute of Technology. Department of Mechanical Engineering 2005-06-02T19:11:21Z 2005-06-02T19:11:21Z 2004 2004 http://hdl.handle.net/1721.1/17920 56794481 Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004. Includes bibliographical references (p. 62-64). The need to understand plastic deformation in amorphous covalently bonded materials arose from the unique mechanical properties of disordered intergranular layers in nc-TiN/a-Si₃N₄ ceramic composites. Silicon was chosen as a model disordered network solid for the purpose of conducting feasible atomistic computer simulations of plastic deformation. Amorphous silicon structures were created by melting and quenching using a molecular dynamics algorithm. These structured were plastically deformed by conjugate gradient static energy minimization. Atomic level analysis was carried out using appropriately generalized notions of stress and strain. Plastic deformation was found to occur in a series of discrete stress relaxations, each one of which was accompanied by a well localized atomic level rearrangement. The transforming regions were roughly ellipsoidal in shape and involved the cooperative motion 100-500 atoms spanning a length scale of 0.7-2.5nm. This length scale is large in comparison to the typical thickness of disordered intergranular layers in nanocrystalline ceramic composites, indicating that the plastic relaxation process in such intergranular layers cannot be the same as the one found in bulk amorphous covalent solids. by Michael J. Demkowicz. S.M. 64 p. 3361803 bytes 3361609 bytes application/pdf application/pdf eng Massachusetts Institute of Technology M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 Mechanical Engineering. Phenomenology and kinematics of discrete plastic deformation events in amorphous silicon : atomistic simulation using the Stillinger-Weber potential Thesis application/pdf Publication unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="9b6f5814-6313-4011-855e-5cb98ee73a56"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Language>eng</Language> <Title>Phenomenology and kinematics of discrete plastic deformation events in amorphous silicon : atomistic simulation using the Stillinger-Weber potential</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2004</PublicationDate> <Authors> <Author> <DisplayName>Demkowicz, Michael J. (Michael John), 1977-</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>http://dspace.mit.edu/handle/1721.1/7582</License> <Keyword>Mechanical Engineering.</Keyword> <Abstract>The need to understand plastic deformation in amorphous covalently bonded materials arose from the unique mechanical properties of disordered intergranular layers in nc-TiN/a-Si₃N₄ ceramic composites. Silicon was chosen as a model disordered network solid for the purpose of conducting feasible atomistic computer simulations of plastic deformation. Amorphous silicon structures were created by melting and quenching using a molecular dynamics algorithm. These structured were plastically deformed by conjugate gradient static energy minimization. Atomic level analysis was carried out using appropriately generalized notions of stress and strain. Plastic deformation was found to occur in a series of discrete stress relaxations, each one of which was accompanied by a well localized atomic level rearrangement. The transforming regions were roughly ellipsoidal in shape and involved the cooperative motion 100-500 atoms spanning a length scale of 0.7-2.5nm. This length scale is large in comparison to the typical thickness of disordered intergranular layers in nanocrystalline ceramic composites, indicating that the plastic relaxation process in such intergranular layers cannot be the same as the one found in bulk amorphous covalent solids.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>