Investigating the behavior of the slow dynamic recovery at early times

Slow dynamics (SD), a type of non-classical nonlinear elastic behavior, is characterized by (i) a material softening due a minor mechanical conditioning and (ii) a subsequent slow recovery that approaches the original macroscopic elastic state. Early work in sandstones and other consolidated granular materials—and more recent work in unconsolidated granular materials—have found the recovery to be logarithmic-in-time, at least for seconds to hours after conditioning. However, other recent studies have observed recoveries in consolidated granular materials that deviate from log(time), particularly for early recovery times. This talk will present experimental investigations in to the nature of the SD recovery, especially at early times. The experimental venue will be the single bead system (a single bead confined between two large plates of a similar material) introduced previously. We will measure SD recoveries using multiple methods, such as Dynamic Acoustic Emission Testing (DAET) and Larsen Monitoring, to better compare our experiments with previous work. The effect of different conditioning mechanisms on the early time recovery will also be investigated. The presentation will conclude with some discussion of proposed mechanisms for slow dynamics.