TY - GEN
T1 - New insights into the physical mechanisms behind slow dynamic nonlinear elasticity
AU - Yoritomo, John Y.
AU - Weaver, Richard L.
N1 - Publisher Copyright:
© "Advances in Acoustics, Noise and Vibration - 2021" Proceedings of the 27th International Congress on Sound and Vibration, ICSV 2021. All rights reserved.
PY - 2021
Y1 - 2021
N2 - 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.
AB - 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.
KW - Slow dynamics diffuse ultrasound
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M3 - Conference contribution
AN - SCOPUS:85117514107
T3 - "Advances in Acoustics, Noise and Vibration - 2021" Proceedings of the 27th International Congress on Sound and Vibration, ICSV 2021
BT - "Advances in Acoustics, Noise and Vibration - 2021" Proceedings of the 27th International Congress on Sound and Vibration, ICSV 2021
A2 - Carletti, Eleonora
A2 - Crocker, Malcolm
A2 - Pawelczyk, Marek
A2 - Tuma, Jiri
PB - Silesian University Press
T2 - 27th International Congress on Sound and Vibration, ICSV 2021
Y2 - 11 July 2021 through 16 July 2021
ER -