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Athermal creep deformation of ultrastable amorphous solids
by Pinaki Chaudhuri, Ludovic Berthier, Misaki Ozawa
Submission summary
| Authors (as registered SciPost users): | Pinaki Chaudhuri |
| Submission information | |
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| Preprint Link: | https://arxiv.org/abs/2501.17952v1 (pdf) |
| Date submitted: | 2025-02-14 11:47 |
| Submitted by: | Chaudhuri, Pinaki |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approaches: | Theoretical, Computational |
Abstract
We numerically investigate the athermal creep deformation of amorphous materials having a wide range of stability. The imposed shear stress serves as the control parameter, allowing us to examine the time-dependent transient response through both the macroscopic strain and microscopic observables. Least stable samples exhibit monotonicity in the transient strain rate versus time, while more stable samples display a pronounced non-monotonic S-shaped curve, corresponding to failure by sharp shear band formation. We identify a diverging timescale associated with the fluidization process and extract the corresponding critical exponents. Our results are compared with predictions from existing scaling theories relevant to soft matter systems. The numerical findings for stable, brittle-like materials represent a challenge for theoretical descriptions. We monitor the microscopic initiation of shear bands during creep responses. Our study encompasses creep deformation across a variety of materials ranging from ductile soft matter to brittle metallic and oxide glasses, all within the same numerical framework.
Author indications on fulfilling journal expectations
- Provide a novel and synergetic link between different research areas.
- Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
- Detail a groundbreaking theoretical/experimental/computational discovery
- Present a breakthrough on a previously-identified and long-standing research stumbling block
Current status:
Reports on this Submission
Strengths
1) The aims of the manuscript are twofold and intersting.
2) the numerical work is careful and at the state of the art
Weaknesses
1) more care to the finite size effect study and sample to sample fluctuations
Report
The manuscript investigates the creep regime at zero temperature in atomistic simulations of amorphous materials with varying degrees of annealing. The authors prepare samples with three different annealing levels and study the strain rate under an applied stress . A threshold stress is identified, σc, which increases for better-annealed materials. For σ<σc , the strain rate exhibits a power-law decay, whereas for σ>σc , the strain rate reaches a minimum before the onset of a fluid shear band.
The aims of the manuscript are twofold: (1) to characterize the threshold , the power-law decay, and the shear band formation time as functions of annealing; (2) to explore the presence of precursors that signal the formation and location of the shear band.
Overall, the manuscript is well written and addresses an interesting problem. However, I have some concerns regarding certain conclusions:
(A) Initial Growth of Strain Rate:
The manuscript does not mention the initial growth of the strain rate. What is the origin of this growth phase? Is it related to an initial elastic response or transient effects?
(B) Power-Law Decay Below :
The authors report that for , the strain rate follows a power-law decay with an exponent expected to be independent of annealing. However, the results indicate a very low exponent in poorly annealed samples, even below unity. This cannot be the long-time decay discussed in Popović et al., since the total strain is the time integral of the strain rate and would diverge for . From Figures 1a and 1b, it seems that at long times, the decay becomes faster. It would be interesting to check whether this corresponds to the expected value or if it transitions to an exponential decay, as mentioned for the short-time dynamics in the supplementary information of Popović et al.
(C) Divergence of Failure Time Near :
The time to failure diverges as . I assume that determining the exponent is challenging due to sample-to-sample fluctuations in for a given annealing degree. Could the authors provide an estimate of these fluctuations in the case of the stable glass?
The second part of the manuscript is more descriptive but highly interesting. From the examples provided, it appears that the plastic deformation map does not allow one to predict where the shear band will form. I find the discussion in its current form appropriate and believe it will be valuable for future studies.
Conclusion:
The manuscript presents a compelling analysis of the creep regime in amorphous materials with varying annealing conditions.
Requested changes
I suggest the authors clarify :
1) the initial strain rate growth
2) further investigate the long-time decay behavior for
3) discuss possible fluctuations in .
Addressing these points would strengthen the conclusions and enhance the overall clarity of the study.
Recommendation
Ask for minor revision