Fluctuations and scaling in creep deformation

TL;DR

This study investigates the spatial fluctuations of deformation during creep in paper samples, revealing increasing fluctuation strength over time and identifying scaling behaviors consistent with phase transition models.

Contribution

It provides experimental evidence of fluctuation scaling in creep deformation and links it to theoretical models of phase transitions and depinning.

Findings

Fluctuation strength increases with time in creep regimes.

Strain rate fluctuations follow a power-law decay with specific exponents.

Experimental results align with depinning transition models.

Abstract

The spatial fluctuations of deformation are studied in creep in the Andrade's power-law and the logarithmic phases, using paper samples. Measurements by the Digital Image Correlation technique show that the relative strength of the strain rate fluctuations increases with time, in both creep regimes. In the Andrade creep phase characterized by a power law decay of the strain rate $\epsilon_t \sim t^{-\theta}$, with $\theta \approx 0.7$, the fluctuations obey $\Delta \epsilon_t \sim t^{-\gamma}$, with $\gamma \approx 0.5$. The local deformation follows a data collapse appropriate for an absorbing state/depinning transition. Similar behavior is found in a crystal plasticity model, with a jamming or yielding phase transition.