Description
- Abstract:
- Inertial microcavitation rheometry (IMR) is an effective method for mechanical characterization of soft materials at high strain rates. In IMR, the dynamics of an isolated bubble is measured, and a theoretical modeling framework is used to extract information regarding the mechanical behavior of the soft material. IMR's ability to provide accurate material characterization at high strain rates relies on the predictive capability of the modeling framework, and this thesis addresses several problems related to robust modeling of inertial microcavitation in soft solids. Modeling approaches based on the Rayleigh-Plesset equation are commonly used but cannot address violent bubble collapse that involves appreciable compressible behavior and limit the nonlinear constitutive models that may be employed. We develop a simulation capability for inertial microcavitation of spherical bubbles, enabling appreciable compressibility to be accounted for and more complex viscoelastic constitutive laws to be incorporated. We apply the capability to understanding the role of compressibility during violent bubble collapse and consider more complex viscoelastic constitutive models for the surrounding material to determine high strain-rate material parameters for polyacrylamide gels. We apply IMR to characterize the mechanical behavior of fixed porcine gray matter. Because brain tissue samples are not optically clear, microcavitation experiments are performed in thin layers, which are constrained between two walls. To account for the thin layer confinement, we develop a two-dimensional axisymmetric finite-element approach, which is a high-fidelity numerical tool that allows us to account for nonlinear interactions between the bubble and the walls. We then apply the framework to estimate the mechanical properties of fixed porcine brain tissue at high-strain rates. We investigate the conditions under which non-spherical instabilities arise due to cavitation dynamics using three-dimensional post-buckling-type simulations. Comparisons are made against a theoretical linear stability analysis, and based on the simulated amplitude of the non-spherical bubble shape, a growth-rate based threshold for the onset of non-spherical instability is proposed. Finally, we develop a three-dimensional finite-element framework to account for material anisotropy by implementing a quadratic standard reinforcing model and study how the bubble aspect ratio depends on anisotropic material properties during inertial microcavitation.
- Notes:
- Thesis (Ph. D.)--Brown University, 2022
Citation
Tzoumaka, Anastasia,
"Aspects of High-Strain-Rate Microcavitation in Soft Solids"
(2022).
Mechanics of Solids Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://repository.library.brown.edu/studio/item/bdr:g2yqn3an/
Relations
Collection:
-
Mechanics of Solids Theses and Dissertations
Theses and Dissertations for the Mechanics of Solids department....