The Strength of Nanoporous Gold: Strain Gradient and Intrinsic Size Effects

2008 ◽  
Author(s):  
Brian Derby ◽  
Rui Dou
Keyword(s):  
Strain Gradient ◽  
Size Effects ◽  
Nanoporous Gold

Scale-Dependent Crack Modeling for Investigation the Effect of Geometrically Necessary Dislocations in Micro/Nano Grain Size of Copper

2016 ◽  
Vol 15 ◽  
pp. 1-16 ◽  
Author(s):  
Amin Zaami ◽  
Ali Shokuhfar
Keyword(s):  
Grain Size ◽  
Stress Concentration ◽  
Strain Gradient ◽  
Stress Concentration Factor ◽  
Size Effects ◽  
Crack Tip ◽  
Length Scale ◽  
State Variables ◽  
Dependent Model ◽  
Homogeneous Strain

In this study, a scale-dependent model is employed to investigate the size effects of copper on the behavior of the crack-tip. This model includes the homogeneous and non-homogeneous strain hardening based on the wavelet interpretation of size effect. Introducing additional micro/nano structural considerations together with decreasing grain size, different size effects can be obtained. As the size dependency is not taken into account in conventional plasticity, an enhanced theory which is related to the strain gradient introduces a length scale will give more realistic representations of state variables near the crack-tip. Accordingly, the contribution of geometrically necessary dislocations (GNDs) activity on strengthening and stress concentration factor is identified in the crack-tip. Finally, the affected zone which is dominated by presence of GNDs is identified

Strain gradient and wavelet interpretation of size effects in yield and strength

2003 ◽  
Vol 35 (8) ◽  
pp. 733-745 ◽  
Author(s):  
I. Tsagrakis ◽  
A. Konstantinidis ◽  
E.C. Aifantis
Keyword(s):  
Strain Gradient ◽  
Size Effects

scholarly journals Flow-induced vibration and stability analysis of carbon nanotubes based on the nonlocal strain gradient Timoshenko beam theory

2018 ◽  
Vol 25 (1) ◽  
pp. 203-218 ◽  
Author(s):  
Reza Bahaadini ◽  
Ali Reza Saidi ◽  
Mohammad Hosseini
Keyword(s):  
Carbon Nanotubes ◽  
Boundary Conditions ◽  
Timoshenko Beam ◽  
Strain Gradient ◽  
Size Effects ◽  
Length Scale ◽  
Governing Equations ◽  
Material Length Scale ◽  
Material Length ◽  
Nonlocal Strain Gradient

A nonlocal strain gradient Timoshenko beam model is developed to study the vibration and instability analysis of the carbon nanotubes conveying nanoflow. The governing equations of motion and boundary conditions are derived by employing Hamilton’s principle, including the effects of moving fluid, material length scale and nonlocal parameters, Knudsen number and gravity force. The material length scale and nonlocal parameters are considered, in order to take into account the size effects. Also, to consider the small-size effects on the flow field, the Knudsen number is used as a discriminant parameter. The Galerkin approach is chosen to analyze the governing equations under clamped–clamped, clamped–hinged and hinged–hinged boundary conditions. It is found that the natural frequency and critical fluid velocity can be decreased by increasing the nonlocal parameter or decreasing the material length scale parameter. Furthermore, it is revealed that the critical flow velocity does not affected by two size-dependent parameters and various boundary conditions in the free molecular flow regime.

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