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Predicting the flow stress and dominant yielding mechanisms: analytical models based on discrete dislocation
Jianqiao Hu1,2, Hengxu Song3, Zhanli Liu4
1State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing, 100190, P R China.
Scientific Reports
|January 2, 2020
Summary
Plasticity in copper crystals depends on strain rate and size. Simulations reveal a shift in yielding mechanisms from dislocation multiplication to surface nucleation in small pillars, explained by new analytical models.
Area of Science:
- Materials Science
- Solid Mechanics
- Computational Materials Science
Background:
- Dislocations drive plasticity in crystalline materials.
- Their collective behavior is influenced by strain rate and sample size.
- Nucleation mechanisms are critical in small-scale specimens.
Purpose of the Study:
- Investigate yielding mechanisms in small copper pillars.
- Understand the transition in nucleation processes.
- Develop predictive models for material strength.
Main Methods:
- Discrete dislocation dynamics (DDD) simulations.
- Simulations on single crystalline copper pillars (100-800 nm diameter).
- Analysis across varying strain rates and sample sizes.
Main Results:
- Observed a transition from dislocation multiplication to surface nucleation.
- Two physics-based analytical models were developed.
- Models accurately predict the transition for different conditions.
Conclusions:
- Analytical models successfully capture the interplay of parameters and nucleation mechanisms.
- Models provide a tool to estimate material strength under various conditions.
- Findings enhance understanding of plasticity in nanomaterials.
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