Analytical and experimental determination of the material intrinsic length scale of strain gradient plasticity theory from micro- and nano-indentation experiments

2004 ◽  
Vol 20 (6) ◽  
pp. 1139-1182 ◽  
Author(s):  
Rashid K. Abu Al-Rub ◽  
George Z. Voyiadjis
Keyword(s):  
Experimental Determination ◽  
Strain Gradient ◽  
Plasticity Theory ◽  
Strain Gradient Plasticity ◽  
Length Scale ◽  
Gradient Plasticity ◽  
Nano Indentation ◽  
Intrinsic Length ◽  
Strain Gradient Plasticity Theory

The correlation between the internal material length scale and the microstructure in nanoindentation experiments and simulations using the conventional mechanism-based strain gradient plasticity theory

2009 ◽  
Vol 24 (3) ◽  
pp. 1197-1207 ◽  
Author(s):  
B. Backes ◽  
Y.Y. Huang ◽  
M. Göken ◽  
K. Durst
Keyword(s):  
Yield Stress ◽  
Strain Gradient ◽  
Plasticity Theory ◽  
Strain Gradient Plasticity ◽  
Length Scale ◽  
Gradient Plasticity ◽  
Hardening Behavior ◽  
Material Length Scale ◽  
Material Length ◽  
Strain Gradient Plasticity Theory

In the present work a new equation to determine the internal material length scale for strain gradient plasticity theories from two independent experiments (uniaxial and nanoindentation tests) is introduced. The applicability of the presented equation is verified for conventional grained as well as for ultrafine-grained copper and brass with different amounts of prestraining. A significant decrease of the experimentally determined internal material length scale is found for increasing dislocation densities due to prestraining. Conventional mechanism strain gradient plasticity theory is used for simulating the indentation response, using experimentally determined material input data as the yield stress, the work-hardening behavior and the internal material length scale. The work-hardening behavior and the yield stress were taken from the uniaxial experiments, whereas the internal material length scale was calculated using the yield stress from the uniaxial experiment, the macroscopic hardness H0 and the length scale parameter h* following from the nanoindentation experiment. A good agreement between the measured and calculated load–displacement curve and the hardness is found independent of the material and the microstructure.

Strain Gradient Plasticity Theory Based on Dislocation - Controlling Mechanism for Nanocrystalline Materials

2010 ◽  
Vol 97-101 ◽  
pp. 2155-2158
Author(s):  
Jian Qiu Zhou ◽  
Lu Ma ◽  
Rong Tao Zhu
Keyword(s):  
Strain Gradient ◽  
Plasticity Theory ◽  
Strain Gradient Plasticity ◽  
Gradient Plasticity ◽  
Two Phase ◽  
Grain Sizes ◽  
Controlling Mechanism ◽  
Model Predictions ◽  
Theory Comparison ◽  
Strain Gradient Plasticity Theory

Due to their dissimilar properties and different deformation mechanisms between grain interior (GI) and grain boundary affected zone (GBAZ) in the nanocrystalline (NC) materials, a two-phase composite model consisting of GI and GBAZ was developed and adopted to build strain gradient plasticity theory. Comparison between experimental data and model predictions at different grain sizes for NC copper shows that the developed method appears to be capable of describing the strain hardening of NC materials.

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