Oscillatory Instabilities in Frictional Granular Matter

Area of Science:

• Physics
• Materials Science
• Geophysics

Background:

• Generic glasses and amorphous solids show plastic instabilities via vanishing real eigenvalues.
• Frictional granular materials possess unique plastic deformation characteristics.

Purpose of the Study:

• To differentiate the plastic responses of frictional granular matter from frictionless amorphous solids.
• To identify novel mechanisms of instability in granular materials.

Main Methods:

• Analysis of Hessian matrix eigenvalues under external strain.
• Investigation of perturbation dynamics in frictional granular systems.

Main Results:

• Frictional granular materials exhibit instabilities through complex eigenvalues, leading to oscillatory growth.
• This mechanism differs fundamentally from the real eigenvalue vanishing seen in glasses.
• Dynamical nonlinearities play a role in taming these perturbations.

Conclusions:

• A new instability mechanism in frictional granular materials is identified.
• This finding is crucial for understanding plasticity and failure in these systems.
• The research has potential implications for earthquake physics.