Dissipation in solids under oscillatory shear: Role of damping scheme and sample thickness

TL;DR

This study investigates how dissipation in solids under oscillatory shear depends on sample thickness and damping scheme, revealing contrasting behaviors for Langevin and DPD damping mechanisms.

Contribution

It provides a comparative analysis of Langevin and DPD damping effects on dissipation as a function of sample thickness in oscillatory shear.

Findings

Dissipation increases with thickness for Langevin damping under strain control.

Dissipation decreases with thickness for DPD damping under strain control.

Under force control, dissipation increases with thickness for both damping schemes.

Abstract

We study dissipation as a function of sample thickness in solids under global oscillatory shear applied to the top layer of the sample. Two types of damping mechanism are considered: Langevin and Dissipative Particle Dynamics (DPD). In the regime of low driving frequency, and under strain-controlled conditions, we observe that for Langevin damping, dissipation increases with sample thickness, while for DPD damping, it decreases. Under force-controlled conditions, dissipation increases with sample thickness for both damping schemes. These results can be physically understood by treating the solid as a one-dimensional harmonic chain in the quasi-static limit, for which explicit equations (scaling relations) describing dissipation as a function of chain length (sample thickness) are provided. The consequences of these results, in particular regarding the choice of damping scheme in computer simulations, are discussed.