Granular gases in mechanical engineering: on the origin of heterogeneous ultrasonic shot peening

TL;DR

This paper models ultrasonic shot peening as a granular gas of inelastic spheres, revealing how inelastic collisions cause significant impact heterogeneity and how shot density influences impact dynamics and temperature profiles.

Contribution

It introduces a granular gas model with variable restitution coefficients to analyze impact heterogeneity and shot density effects in ultrasonic shot peening.

Findings

Heterogeneous impact distribution increases with inelastic collisions.

Impact heterogeneity is much larger than boundary collision effects.

Shot density affects impact velocities, angles, and temperature profiles.

Abstract

The behavior of an ultrasonic shot peening process is observed and analyzed by using a model of inelastic hard spheres in a gravitational field that are fluidized by a vibrating bottom wall (sonotrode) in a cylindrical chamber. A marked heterogeneous distribution of impacts appears when the collision between the shot and the side wall becomes inelastic with constant dissipation. This effect is one order of magnitude larger than the simple heterogeneity arising from boundary collision on the cylinder. Variable restitution coefficients bring the simulation closer to the general observation and allows the investigation of peening regimes with changing shot density. We compute within this model other physical quantities (impact velocities, impact angle, temperature and density profile) that are influenced by the number $N$ of spheres.