Type
Text
Type
Dissertation
Advisor
Advisors: Venkatesh, T. A.; Koga, Tad; Raghothamachar, Balaji; Hwang, David
Date
2017-08-01
Keywords
Materials science, Indentation, Model Size Effects, Porous Media, Thin Films, Transversely Isotropic, Woven Matrix
Department
Department of Materials Science and Engineering
Language
en
Source
This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree.
Identifier
http://hdl.handle.net/11401/78319
Publisher
The Graduate School, Stony Brook University: Stony Brook, NY.
Format
application/pdf
Abstract
A finite element model that captures the indentation force-depth response of a thin film system that exhibits isotropic elastic behavior and transversely isotropic plastic behavior on a substrate material that exhibits isotropic elastic behavior, indented by a sharp conical indenter was developed. Using dimensional analysis and a large number of finite element simulations, the relationships between the indentation response and the fundamental elastic and plastic properties of the substrate and the thin film were captured. It is demonstrated that both the forward analysis that predicts the indentation response from known material properties and the reverse analysis that predicts the material properties from known indentation responses were captured accurately. It is also demonstrated that the substrate’s elastic property could also be simultaneously obtained along with the elastic and plastic properties of the indented thin film from the indentation analysis. Under conditions where the experimental results are very reliable with small errors, and within the range of material systems investigated in this study, the indentation method is expected to provide unique, robust and reliable predictions for the elastic and plastic properties of the thin film system. A hybrid finite element/volume model that captures the flow and pressure drop characteristics in highly porous woven matrix media is developed. It is demonstrated that the geometric characteristics of a real woven matrix comprised of circular cross-section fibers and curvature due to fiber bending is captured well with an equivalent model system comprised of fibers with square cross-section. A comprehensive study of the effects of changes in the finite element model size and defects in lay-up of the woven matrix layers on the predictions of the pressure drops was carried out. Changes in the in-plane size of the finite element model, lateral to the fluid flow direction, had relatively minor effects on the pressure drops predicted by the models. However, changes in the thickness of the finite element model in the fluid flow direction had significant effects on the pressure drops. In simulations with very thin models, the boundary effects had a greater influence on the overall flow behavior and caused the predicted pressure drops to increase proportionately. On the other hand, simulations with thick models indicated that the flows were fully developed and the boundary effects were minimized, resulting in relatively smaller pressure drops. Furthermore, defects in the lay-up of the woven matrix layers were also shown to have a significant impact on the pressure drops predicted by the simulations. Higher defect densities resulted in greater pressure drops as they disrupted the steady flow of fluid in the through-thickness direction. The pressure drops obtained in the finite element model simulations of thick models that contained some defective layers matched very well with experimental observations. | 165 pages
Recommended Citation
Zhi, Zheng, "Computational Modeling of Indentation of Thin Films and Flow Through Porous Media" (2017). Stony Brook Theses and Dissertations Collection, 2006-2020 (closed to submissions). 3813.
https://commons.library.stonybrook.edu/stony-brook-theses-and-dissertations-collection/3813