First Advisor
Tyler Engstrom
Degree Name
Bachelor of Science
Document Type
Capstone
Date Created
5-10-2025
Department
College of Natural and Health Sciences, Physics and Astronomy, Physics and Astronomy Student Work
Abstract
This research experimentally investigates creasing behavior on the inner surface of hemispherical shells with the ultimate goal of modelling the formation of the foveal pit, a sharp surface deformation present in the retina of the eye of many animals. Creasing is a phenomenon observed in hyperelastic materials and is characterized by sharply localized surface deformations that appear at ~35% compressive strain. The foveal pits of anoles (small iguanian lizards) are funnel-shaped and resemble creases when cut along the central axis. Furthermore, during foveal pit formation the anole eye contracts around 35% along this same axis. Given these similarities we believe that creasing may be the primary mechanism that drives the formation of the pit. In an effort to test this possibility, prior creasing experiments involving everted elastomer tubes were first replicated and then extended to hemispherically-capped tubes. This method provided a stable configuration of the sample tubes that allowed for imaging of the inner surface while subject to compressive stress. Though these experiments did not produce dimple-like deformations on these surfaces, they did yield several creasing patterns that differ in character depending on the degree of compression. The results of this work lead into further experiments currently being conducted using a vacuum apparatus and elastic membrane to test a recently hypothesized intraocular pressure-driven creasing mechanism.
Abstract Format
html
Disciplines
Biological and Chemical Physics | Condensed Matter Physics | Statistical, Nonlinear, and Soft Matter Physics
Keywords
fovea; foveal; pit; crease; creasing; wrinkling; eversion
Language
English
Extent
29 pages
Rights Statement
Copyright is held by the author.
Recommended Citation
Peppard, Indigo Skye, "Creasing in Thick Hemispherical Shells as a Model for Foveal Formation" (2025). Undergraduate Honors Theses. 124.
https://digscholarship.unco.edu/honors/124
Included in
Biological and Chemical Physics Commons, Condensed Matter Physics Commons, Statistical, Nonlinear, and Soft Matter Physics Commons
