Abstract

The micropillar compression test is a novel experiment to study the mechanical properties of materials at small length scales of micro and nano. The results of the micropillar compression experiments show that the strength of the material depends on the pillar diameter, which is commonly termed as size effects. In the current work, first, the experimental observations and theoretical models of size effects during micropillar compression tests are reviewed in the case of crystalline metals. In the next step, the recent computer simulations using molecular dynamics are reviewed as a powerful tool to investigate the micropillar compression experiment and its governing mechanisms of size effects.

Highlights

  • The current work reviews the size effects, during micropillar compression experiments

  • The results showed that the governing mechanisms of size effects depend on the size of the pillar in a way that the mechanisms changed from dislocation starvation, which is a special subset of source exhaustion mechanism, for very small samples to the forest hardening mechanism for larger samples

  • 0.25 to investigate the presented results is to show the responsesStrain of both pillars at similar strain rates, as shown in Figure 23.5 The results show that, as the strain rate decreases, more size effects are observed

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Summary

Introduction

The current work reviews the size effects, during micropillar compression experiments. The focus of this work is on the governing mechanisms of size effects for crystalline metals during micropillar compression tests. The results showed that the governing mechanisms of size effects depend on the size of the pillar in a way that the mechanisms changed from dislocation starvation, which is a special subset of source exhaustion mechanism, for very small samples to the forest hardening mechanism for larger samples. Another aspect that is addressed here is to study the coupling effects of size and strain rate during the micropillar compression experiment. The observed trend can justify why the observed size effects in MD simulation is different from those of the quasi-static experiments

Experimental Observations
Comparison of and power exponents
Size Effects Models
Dislocation Source Truncation Mechanism
Dislocation Source Exhaustion Mechanism
Weakest
Atomistic
15. The responses ofof samples compression in the cases of pillars
16. The between the the responses responsesof ofthe thepillar pillarwith withH
Conclusions
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