Despite myriad challenges, clinicians see room for progress.
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Communicated by Zdenek P. Bazant, Northwestern University, Evanston, IL, October 3, 2005 (received for review April 19, 2005)
Article Figures & SI
Figures
- Fig. 1.
Self-similar experiments in pure tension Cu films. Comparison between the mechanical response of submicronic ultrafine-grained thin films (MDE) and millimeter-thick coarse-grained films (Fullam tensile stage).
- Fig. 2.
TEM and SEM observations on MDE-tested Au films. (a and b) Study of the plastic activity of 0.3-μm-thick Au films (a) (SEM picture showing the fracture surface) and 1-μm-thick Au films (b) (SEM picture showing large deformation slip bands close to the fracture edge). (c) Cross-sectional TEM view of fracture region. (d) High-aspect-ratio grain exhibiting dislocation network.
- Fig. 3.
Problem definition for DDD calculations. (a) Columnar grains simulating by rectangular boxes with various heights. (b) Present study: single crystal (grain) considered as a rectangular box [thickness: h; grain size: d with a crystallographic direction
perpendicular to the film plane (consistent with the strong 〈111 〉 texture of the film) and with an applied tensile loading parallel to the 〈112 〉 direction (arbitrary)]. The sides are impenetrable to simulate grain boundaries, and the top and bottom faces are attractive to represent free surfaces. - Fig. 4.
Thickness effect obtained by DDD calculations for different thicknesses (h = 0.2, 0.4, 0.6, and 1 μm) considering a freestanding columnar grain. The error bars represent the statistical scatter of different runs at the end of the simulation for each sample. (a) Source density = 2.4 × 104 per cm. (b) Source density = 0.8 × 104 per cm.
- Fig. 5.
Final dislocation configurations for an applied strain of 0.8% [top view (Left), 3D view (Right)]. (a) 0.2-μm sample. (b) 0.6-μm sample. (c) 1-μm sample.
- Fig. 6.
Flow stress (defined as the stress corresponding to 0.2% permanent deformation upon elastic unloading) as a function of film thickness inverse.
Data supplements
Espinosa et al. 10.1073/pnas.0508572102.
Supporting Movies
Files in this Data Supplement:
Supporting Movie 1
Supporting Movie 2
Supporting Movie 3
Supporting Movie 4
Supporting Movie 5
Supporting Movie 1Movie 1. Microstructure evolution recorded by optical imaging.
Supporting Movie 2Movie 2. Local strain fields obtained by digital image correlation.
Supporting Movie 3Movie 3. Discrete dislocation plasticity simulation of the 0.2-μm-thick sample.
Supporting Movie 4Movie 4. Discrete dislocation plasticity simulation of the 0.6-μm-thick sample.
Supporting Movie 5Movie 5. Discrete dislocation plasticity simulation of the 1 μm-thick sample.
An interpretation of size-scale plasticity in geometrically confined systems
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