Journal ArticleDOI
Indentation size effects in crystalline materials: A law for strain gradient plasticity
William D. Nix,Huajian Gao +1 more
TLDR
In this article, the indentation size effect for crystalline materials can be accurately modeled using the concept of geometrically necessary dislocations, which leads to the following characteristic form for the depth dependence of the hardness: H H 0 1+ h ∗ h where H is the hardness for a given depth of indentation, h, H 0 is a characteristic length that depends on the shape of the indenter, the shear modulus and H 0.Abstract:
We show that the indentation size effect for crystalline materials can be accurately modeled using the concept of geometrically necessary dislocations. The model leads to the following characteristic form for the depth dependence of the hardness: H H 0 1+ h ∗ h where H is the hardness for a given depth of indentation, h, H0 is the hardness in the limit of infinite depth and h ∗ is a characteristic length that depends on the shape of the indenter, the shear modulus and H0. Indentation experiments on annealed (111) copper single crystals and cold worked polycrystalline copper show that this relation is well-obeyed. We also show that this relation describes the indentation size effect observed for single crystals of silver. We use this model to derive the following law for strain gradient plasticity: ( σ σ 0 ) 2 = 1 + l χ , where σ is the effective flow stress in the presence of a gradient, σ0 is the flow stress in the absence of a gradient, χ is the effective strain gradient and l a characteristic material length scale, which is, in turn, related to the flow stress of the material in the absence of a strain gradient, l ≈ b( μ σ 0 ) 2 . For materials characterized by the power law σ 0 = σ ref e 1 n , the above law can be recast in a form with a strain-independent material length scale l. ( builtσ σ ref ) 2 = e 2 n + l χ l = b( μ σ ref ) 2 = l ( σ 0 σ ref ) 2 . This law resembles the phenomenological law developed by Fleck and Hutchinson, with their phenomenological length scale interpreted in terms of measurable material parametersbl].read more
Citations
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Journal ArticleDOI
A finite element framework for distortion gradient plasticity with applications to bending of thin foils
TL;DR: In this article, a general purpose finite element framework is presented to study small-scale metal plasticity, where a distinct feature of the adopted distortion gradient plasticity formulation is the constitutive inclusion of the plastic spin, as proposed by Gurtin, through the prescription of a free energy dependent on Nye's dislocation density tensor.
Journal ArticleDOI
Individual strain gradient effect on torsional strength of electropolished microscale copper wires
TL;DR: In this article, a significant strain gradient effect is confirmed in wire torsion by electropolishing the wires with an initial diameter of 50μm at room temperature for different time periods.
Journal ArticleDOI
Taylor-based nonlocal theory of plasticity: numerical studies of the micro-indentation experiments and crack tip fields
TL;DR: The Taylor-based nonlocal theory (TNT) of plasticity as mentioned in this paper was developed from the Taylor dislocation model for this purpose and applied to study micro-indentation experiments.
Journal ArticleDOI
Microstructural and fatigue behavior of cold sprayed Ni-based superalloys coatings
Pasquale Cavaliere,A. Silvello,A. Silvello,Nuria Cinca,H. Canales,Sergi Dosta,I. Garcia Cano,J.M. Guilemany +7 more
TL;DR: In this article, the microstructural and mechanical properties of Ni-based superalloys coatings, cold sprayed on C steel substrates, are analyzed using optical and scanning electron microscopy.
Journal ArticleDOI
Irradiation resistance of MAX phases Ti3SiC2 and Ti3AlC2: Characterization and comparison
Qing Huang,Renduo Liu,Guanhong Lei,Hefei Huang,Jianjian Li,Suixia He,Dehui Li,Long Yan,Jie Zhou +8 more
TL;DR: In this paper, the microstructural evolution and the changes in mechanical properties of 7 MeV Xe26+-ion-irradiated Ti3SiC2 and Ti3AlC2 were investigated.
References
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Journal ArticleDOI
The deformation of plastically non-homogeneous materials
TL;DR: The geometrically necessary dislocations as discussed by the authors were introduced to distinguish them from the statistically storages in pure crystals during straining and are responsible for the normal 3-stage hardening.
Journal ArticleDOI
Strain gradient plasticity: Theory and experiment
TL;DR: In this paper, a deformation theory of plasticity is introduced to represent in a phenomenological manner the relative roles of strain hardening and strain gradient hardening, which is a non-linear generalization of Cosserat couple stress theory.
Journal ArticleDOI
A phenomenological theory for strain gradient effects in plasticity
TL;DR: In this paper, a strain gradient theory of plasticity is introduced, based on the notion of statistically stored and geometrically necessary dislocations, which fits within the general framework of couple stress theory and involves a single material length scale l.
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