Fluctuations and scaling in creep deformation

Area of Science:

• Materials Science
• Physics
• Solid Mechanics

Background:

• Creep deformation is a time-dependent mechanical behavior observed in materials under constant stress.
• Understanding spatial fluctuations in deformation is crucial for predicting material failure and performance.
• Andrade and logarithmic creep regimes represent distinct phases of material response over time.

Purpose of the Study:

• To investigate the spatial fluctuations of deformation during creep in Andrade and logarithmic phases.
• To quantify the evolution of strain rate fluctuations over time.
• To explore the relationship between deformation fluctuations and phase transition phenomena.

Main Methods:

• Experimental analysis of paper samples under creep conditions.
• Utilizing digital image correlation (DIC) technique for precise deformation measurement.
• Analysis of strain rate fluctuations (Δϵt) and their temporal evolution (t).
• Comparison with a crystal plasticity model.

Main Results:

• The relative strength of strain rate fluctuations increases with time in both creep regimes.
• In Andrade creep (ϵt∼t(-θ), θ≈0.7), fluctuations follow Δϵt∼t(-γ), with γ≈0.5.
• Local deformation exhibits a data collapse indicative of a phase transition.
• Similar behaviors were observed in a crystal plasticity model, suggesting jamming or yielding transitions.

Conclusions:

• Spatial deformation fluctuations intensify over time during creep.
• The observed data collapse points to a phase transition mechanism governing local deformation.
• The findings are consistent with jamming or yielding transitions in crystal plasticity models.
• This study provides insights into the fundamental mechanisms of creep and material instability.