Award Date

December 2023

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geoscience

First Committee Member

Pamela Burnley

Second Committee Member

Michael Wells

Third Committee Member

Margaret Odlum

Fourth Committee Member

Brendan O'Toole

Number of Pages

118

Abstract

Shear strain localization is typical in deforming rocks and is vital for developing faults and tectonic boundaries. There are various proposed drivers of shear localization (temperature, fluid, phase transformation, and microstructure); we will explore the effects of elastic heterogeneity (a microstructural influence) on shear localization in polycrystal models. Elastic heterogeneity can lead to varied stress states in material and drive shear localization. Previous simulations of elastically heterogeneous polycrystal models have shown that the stress distribution can be described as forming an anastomosing pattern of high-stress streams parallel to the compression direction. This anastomosing patterning resembles force chains; linear, high-stress features that form parallel to compression in granular materials. Findings in the literature suggest that buckling force chains govern shear band formation in granular materials; thus, viewing polycrystalline materials through a force chain lens may bring new insights. In previous simulation work, the initiation of plastic deformation produced shear bands with a spacing proportional to the density of patterning in the stress distribution and with displacements that are inversely proportional to the number of shear bands that formed. We continue this work by attempting to quantify the spacing of force chains and shear bands in 2D simulations of polycrystals using the Autoperiod method. The Autoperiod method can measure the dominant periodicities of a signal and is adapted to capture spatial periodicities of features in the stress and strain distributions from polycrystalline models. This quantification may allow us to make testable predictions about the distribution of stress and strain localization in real materials.

Keywords

Deformation; Finite Element Method; Force Chains; Spatial Periodicity; Strain Localization; Stress Percolation

Disciplines

Geophysics and Seismology

File Format

pdf

File Size

24910 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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