Nucleation of large avalanches

Long, Alan

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https://hdl.handle.net/2142/117758 Copy

Description

Title

Nucleation of large avalanches

Author(s)

Long, Alan

Issue Date

2022-11-22

Director of Research (if dissertation) or Advisor (if thesis)

Dahmen, Karin A

Doctoral Committee Chair(s)

Weissman, Micheal B

Committee Member(s)

• Gadway, Bryce
• Faulkner, Thomas

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Avalanches
• Plasticity
• Deformation
• Nucleation
• Bulk Metallic Glass
• Shear Band

Abstract

Under slow forcing, many solids deform intermittently via slip avalanches. Examples include bulk metallic glasses (BMGs) [1 – 3], granular media [4 – 6] and high entropy alloys [7]. In each case, experiments show a wide range of avalanche sizes. Understanding the details of the mechanisms for these behaviors is critical to safely using these materials in applications and developing microstructural design principles to tailor mechanical properties. For applications, the large avalanches can be disastrous, as they typically cut through the entire sample. Despite its importance, the behavior of large avalanches has until now been largely unknown. Using a simple mean-field model [2,8], high resolution experiments, and computational simulations, we elucidate the properties of these large avalanches in both BMGs and granular media. We discuss the nucleation mechanism by which the large avalanches form. Both the model and experiments with BMGs show precursory “rumbling” before many of the large avalanches. This rumbling is the nucleation phase for a large event. We also discuss and analyze the brittleness and ductility of BMG composites with microscale crystalline precipitates and BMGs that do not contain crystallites. We determine the dependence of the large avalanche statistics on stress and the hardening of the material. Finally we compare the large avalanche statistics of BMGs and granular materials. Despite significant differences in the structure and stress-strain behavior, the statistics of the avalanches for both materials follow similar trends with respect to both their large and small events. We develop and use new methods to characterize the propagation dynamics in these materials.

Graduation Semester

2022-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Alan Long

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