What triggers failure in frictional granular assemblies?

Area of Science:

• Physics
• Materials Science
• Engineering Mechanics

Background:

• Granular materials exhibit complex behaviors under stress.
• Understanding yielding and failure is crucial for material design and safety.

Purpose of the Study:

• To numerically investigate the yielding and failure mechanisms of small granular packings.
• To identify the critical events and energy transformations preceding catastrophic failure.

Main Methods:

• Numerical simulations of granular packings under deviatoric stress.
• Analysis of contact status changes and stiffness matrix properties.
• Examination of energy flux and transformations during failure.

Main Results:

• Packing softening and increased sliding contacts correlate with rising load.
• A specific contact status change consistently triggers packing collapse.
• Mechanical instability or neutral stability often follows critical contact changes.
• Energy converts from potential to kinetic upon failure, with force disequilibrium becoming a dominant source.

Conclusions:

• Failure in granular packings is initiated by identifiable contact status changes.
• These changes can lead to mechanical instabilities and rapid energy release.
• The transition from stored potential energy to kinetic energy characterizes the failure process.