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Unique universal scaling in nanoindentation pop-ins
Yuji Sato1, Shuhei Shinzato1, Takahito Ohmura2,3,4
1Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.
Nature Communications
|August 23, 2020
Summary
This study reveals power-law statistics in nanoindentation plasticity, shifting from Gaussian-like behavior for the first pop-in to power-law for subsequent events. This transition indicates a change in material deformation mechanisms under sharp indentation.
Area of Science:
- Materials Science
- Solid Mechanics
- Physics of Materials
Background:
- Power laws are frequently observed in various scientific disciplines, including the study of material plasticity.
- Understanding deformation mechanisms is crucial for predicting material behavior under stress.
Purpose of the Study:
- To investigate the statistical nature of pop-in events during load-controlled nanoindentation.
- To identify the underlying deformation mechanisms responsible for observed statistical transitions.
- To compare nanoindentation plasticity with other deformation regimes like micro-pillar plasticity.
Main Methods:
- Load-controlled nanoindentation experiments were performed on body-centered cubic (BCC) iron and face-centered cubic (FCC) copper.
- Statistical analysis of pop-in magnitudes was conducted, focusing on the transition from initial to subsequent events.
- Analysis of stress and dislocation density fields induced by sharp indentation.
Main Results:
- The first pop-in event exhibits Gaussian-like statistics, while subsequent pop-ins follow power-law statistics.
- A transition in deformation mechanisms from dislocation nucleation to dislocation network evolution was identified.
- Scaling exponents for power laws were determined for BCC iron (5.6 and 3.9) and FCC copper (6.4).
Conclusions:
- Nanoindentation plasticity exhibits distinct statistical characteristics compared to micro-pillar plasticity.
- The observed power-law exponents in nanoindentation are significantly higher than those in micro-pillar plasticity.
- These findings suggest that nanoindentation plasticity belongs to a different universality class.
