Simulation of nanopowder high-speed compaction by 2d granular dynamics method

TL;DR

This study models high-speed nanopowder compaction using a 2D granular dynamics approach, revealing a power-law relationship between pressure and strain rate, and analyzing stress relaxation post-compression.

Contribution

It introduces a comprehensive 2D granular dynamics model that includes dispersive attraction and bonding, providing new insights into strain rate effects on nanopowder densification.

Findings

Pressure follows a p ∝ v^{1/4} power-law dependence on strain rate.

Densification curves vary with different compression rates.

Stress relaxation behavior post-compression was characterized.

Abstract

The paper concerns the nanopowder high-speed, $10^4$ - $10^9$ s${}^{-1}$, compaction processes modeling by a two-dimensional granular dynamics method. Nanoparticles interaction, in addition to known contact laws, included dispersive attraction, formation of a strong interparticle bonding (powder agglomeration) as well as the forces caused by viscous stresses in the contact region. For different densification rates, the "pressure vs. density" curves (densification curves) were calculated. Relaxation of the stresses after the compression stage was analyzed as well. The densification curves analysis allowed us to suggest the dependence of compaction pressure as a function of strain rate. It was found that in contrast to the plastic flow of metals, where the yield strength is proportional to the logarithm of the strain rate, the power-law dependence of applied pressure on the strain rate as $p\propto v^{1/4}$ was established for the modeled nanosized powders.