Effect of Random Pinning on the Yielding Transition of Amorphous Solid under Oscillatory Shear

TL;DR

This study explores how random pinning of particles in a glass-forming system affects its yielding transition under oscillatory shear, revealing that increased pinning shifts the material from fragile to strong glass behavior and suppresses shear band formation.

Contribution

It demonstrates how random pinning alters the fragility and yielding behavior of amorphous solids, providing new insights into the control of mechanical response in glassy materials.

Findings

Pinning increases system fragility from fragile to strong.

Random pinning suppresses shear band formation.

Yielding transition varies significantly with pinning fraction.

Abstract

We investigate the effects of random pinning, where we freeze the relaxation degrees of freedom for a fraction of randomly selected particles, on the yielding transition under oscillatory shear through extensive computer simulations. Using Kob-Anderson model as our model glass former, we pin a fraction of the particles. These pinned particles can move affinely under the imposed oscillatory shear deformation but are not allowed to relax through subsequent rearrangements due to plastic events. As the fraction of pinned particles increases, the system transitions from being a fragile glass former to a strong glass former. This gives us opportunity to examine how changes in fragility impact the yielding transition. Our results demonstrate notable differences in the yielding transition between strong and fragile glass formers under random pinning. This aligns with previous observations where fragility was altered by changing the packing fraction in soft sphere model albeit with a main difference that random pinning significantly suppresses the formation of shear bands, even in well-annealed glass samples.