New insights into the physical mechanisms behind slow dynamic nonlinear elasticity

John Y. Yoritomo, Richard L. Weaver

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Slow dynamic nonlinearity is characterized by a logarithmic recovery after an initial drop of material stiffness, induced by a mechanical conditioning. It appears to be ubiquitous in brittle materials with complex heterogeneous or cracked microstructures, such as rocks, concrete and cracked glass blocks. A satisfactory understanding of the physical mechanisms behind slow dynamics remains elusive, as does its universality and the log(time) recovery. Here we introduce two simplified systems that exhibit slow dynamics to provide new insights for theoretical consideration. The first system is composed of unconsolidated bead packs. Slow dynamics has been observed in this system previously. However, particular care is used here in the experimental design to overcome the difficulties inherent in bead pack studies. This includes the design of the bead pack support, the use of very low frequency conditioning, and the use of ultrasonic waves as a probe with coda wave interferometry to assess changes. The second system is even simpler-a single bead confined between two large plates. This system is designed with a view towards rapid control of the contact zone environment. It is again probed by ultrasonic waves, and changes are assessed with coda wave interferometry. We present slow dynamic results for both glass and metal versions of the two systems. Our results imply that some previously proposed mechanisms-force chains, glassy microstructures, and cracking-cannot play essential roles as they are presumably absent in one or more of the studied systems.

Original languageEnglish (US)
Title of host publication"Advances in Acoustics, Noise and Vibration - 2021" Proceedings of the 27th International Congress on Sound and Vibration, ICSV 2021
EditorsEleonora Carletti, Malcolm Crocker, Marek Pawelczyk, Jiri Tuma
PublisherSilesian University Press
ISBN (Electronic)9788378807995
StatePublished - 2021
Event27th International Congress on Sound and Vibration, ICSV 2021 - Virtual, Online
Duration: Jul 11 2021Jul 16 2021

Publication series

Name"Advances in Acoustics, Noise and Vibration - 2021" Proceedings of the 27th International Congress on Sound and Vibration, ICSV 2021

Conference

Conference27th International Congress on Sound and Vibration, ICSV 2021
CityVirtual, Online
Period7/11/217/16/21

Keywords

  • Slow dynamics diffuse ultrasound

ASJC Scopus subject areas

  • Acoustics and Ultrasonics

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