Stress transmission through three-dimensional granular crystals with stacking faults

TL;DR

This study investigates how stacking fault defects influence force transmission in 3D face-centered-cubic granular crystals, revealing that stacking faults significantly alter force response patterns and can transform crystal behavior towards hexagonal-close-packed structures.

Contribution

It provides a detailed analysis of stacking fault effects on force transmission in 3D granular crystals, linking defect configurations to force response patterns and crystal structure evolution.

Findings

Stacking faults act as boundaries between different FCC stacking orders.

Force response patterns are predictable based on defect geometry.

Increasing stacking faults shifts force patterns toward HCP crystal behavior.

Abstract

We explore the effect of stacking fault defects on the transmission of forces in three-dimensional face-centered-cubic granular crystals. An external force is applied to a small area at the top surface of a crystalline packing of granular beads containing one or two stacking faults at various depths. The response forces at the bottom surface are measured and found to correspond to predictions based on vector force balance within the geometry of the defects. We identify the elementary stacking fault as a boundary between two pure face-centered-cubic crystals with different stacking orders. Other stacking faults produce response force patterns that can be viewed as resulting from repetitions of this basic defect. As the number of stacking faults increases, the intensity pattern evolves toward that of an hexagonal-close-packed crystal. This leads to the conclusion that the force pattern of that crystal structure crystal can be viewed as the extreme limit of a face-centered-cubic crystal with a stacking fault at every layer.