Dissertation
Dislocation interactions with interfaces
Washington State University
Doctor of Philosophy (PhD), Washington State University
08/2009
DOI:
https://doi.org/10.7273/000005992
Abstract
In this dissertation work, our main focus was to investigate the interactions of dislocation with interfaces. Plastic deformation in polycrystalline materials and multi-layered metallic composites, on a microscopic scale, involve interaction of dislocations with grain boundaries and bi-material interfaces respectively. Towards the end of investigating the interaction of dislocations with bi-material interface, we have derived analytical expressions for the stress field due to an arbitrary dislocation segment in an isotropic inhomogeneous medium. We have developed a new approach as compared with attempts made in the literature. One of the main advantages our derivation is separation of solution into homogeneous and image parts which facilitates an easy modification of existing dislocation dynamics simulation codes to incorporate the image stress effect. In the case of polycrystalline materials, as grain boundaries are major obstacles to plastic deformation, it is of fundamental importance to study the interactions of dislocations with grain boundaries. Towards this goal, in chapter four, we have investigated the basic phenomena of transmission of dislocation through a pure tilt wall. In this work, we have studied the structure of the symmetric tilt wall acquired after transmission of several dislocations and modeled the structures to which it relaxes. In chapter five, digressing from the main theme of the dissertation, we have studied the kinematic and thermodynamics effect of representing discrete dislocations in terms of continuously distributed dislocations. In this work, we have considered infinite stacked double ended pile-ups in an isotropic elastic homogeneous medium. The error in number of dislocations, microstructural energy and slip distribution between discrete and semi-discrete representation was quantified. The asymptotic expressions are derived and threshold values of certain key parameters are also deduced. In the appendix, we have investigated the deformation of single crystal micropillars under uniaxial compression using a multi-scale model for plasticity. Our simulation results are qualitatively and quantitatively comparable with that of experiments. Dislocation arm operation was found to be the prominent mechanism to plastic deformation in micron to submicron size specimens. The observed strain hardening is attributed to the formation of entangled dislocation structures and stagnation of dislocations.
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Details
- Title
- Dislocation interactions with interfaces
- Creators
- Sreekanth Akarapu
- Contributors
- Hussein M. Zbib (Chair)Sinisa Mesarovic (Committee Member)David P Field (Committee Member) - Washington State University, School of Mechanical and Materials EngineeringAlexander Panchenko (Committee Member) - Washington State University, Department of Mathematics and Statistics
- Awarding Institution
- Washington State University
- Academic Unit
- School of Mechanical and Materials Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 202
- Identifiers
- 99901055132801842
- Language
- English
- Resource Type
- Dissertation