Ultrasonic probing of the elastic properties of PMMA bead packings and their rearrangement during pressure sintering

TL;DR

This study uses ultrasound to monitor elastic property changes in PMMA bead packings during pressure sintering, revealing bonding effects and granular rearrangements through velocity measurements and speckle correlation.

Contribution

It introduces a combined ultrasonic and speckle correlation method to analyze elastic properties and granular rearrangements during sintering, highlighting bonding effects.

Findings

Velocity data align with contact model predictions

Bonding significantly influences mechanical behavior

Granular rearrangements occur before sintering onset

Abstract

Ultrasound transmission in PMMA spherical bead packings is investigated during the sintering process under stress. Velocity and amplitude measurements of coherent longitudinal waves are performed to monitor the evolution of the elastic properties of the solid frame from noncohesive packing to sintered granular material. Comparison between the experimental velocity data and the prediction by a contact model [Digby, J. Appl. Mech. 48, 803, (1981)] reveals the crucial role of the bonding effect on the mechanical behavior of granular compacts. By using the correlation technique of acoustic speckles, we also observe the important rearrangements in granular packings before the onset of sintering.