Nucleation of large avalanches

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Long, Alan

Contributors dc:contributor

• Dahmen, Karin A
• Weissman, Micheal B
• Gadway, Bryce
• Faulkner, Thomas

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

Statement dc:rights

• Copyright 2022 Alan Long

Language dc:language

en, eng

Handle dc:identifier

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

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F117758