arXiv subjects

Tommaso Pettinari

Publications and source records attributed to Tommaso Pettinari.

2 recordsLinked to original sources

arXiv2026

The motion of intruders through soft solids

We present the results of an experimental investigation into the motion of large buoyant rigid spheres rising through highly concentrated collections of hydrated hydrogel particles. The concentration of the soft highly poro-elastic particles is such that the mechanical properties of the material are that of a soft solid which can also flow very slowly. Despite the established time-dependent, non-Newtonian character of hydrogel packings, we findthat when the upper surface of the material is free, an immersed buoyant sphere travels through the material at a constant speed. Qualitatively distinct behavior is found when a rigid lid is placed on the surface of the material. In these cases, sublinear time-dependent motion of the sphere is found. The effects of the motion are generally observed to be highly localised around the sphere in all cases. However, when the translational speed of the sphere is constant, it is accompanied by significant flow at the surface of the sample whereas surface movement is suppressed when a lid is present. When the stress exerted on the material is changed by varying the mass of the sphere, its terminal velocity is found to depend exponentially on buoyancy. We use these observations to support a hypothesis which links the exponential stress dependence of the drag coefficient induced by the material to the effects of the boundary conditions on the kinematics of the intruder.

cond-mat.soft↗

arXiv2024

Elasticity of self-organized frustrated disordered spring networks

There have been some interesting recent advances in understanding the notion of mechanical disorder in structural glasses and the statistical mechanics of these systems' low-energy excitations. Here we contribute to these advances by studying a minimal model for structural glasses' elasticity in which the degree of mechanical disorder -- as characterized by recently introduced dimensionless quantifiers -- is readily tunable over a very large range. We comprehensively investigate a number of scaling laws observed for various macro-, meso- and microscopic elastic properties, and rationalize them using scaling arguments. Interestingly, we demonstrate that the model features the universal quartic glassy vibrational density of states as seen in many atomistic and molecular models of structural glasses formed by cooling a melt. The emergence of this universal glassy spectrum highlights the role of self-organization (towards mechanical equilibrium) in its formation, and elucidates why models featuring structural frustration alone do not feature the same universal glassy spectrum. Finally, we discuss relations to existing work in the context of strain-stiffening of elastic networks and of low-energy excitations in structural glasses, in addition to future research directions.

cond-mat.soft↗