Novel nickle foil micro-bend tests and the need for a relook at length scale parameter’s numerical value
TL;DR: In this paper, the authors provide a discussion on two aspects of size effects which is known to be a characteristic behavior of micro-scaled structures and provide the experimentalists with a novel...
Abstract: The current study provides a discussion on two aspects of size-effects which is known to be a characteristic behavior of micro-scaled structures. First it provides the experimentalists with a novel...
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TL;DR: In this article , the couple stress and strain gradient theory have been used to predict the mechanical behavior of micro/nano-scale structures, and the increase of bending rigidity is analyzed based on couple stress theory and the length scale parameter is measured as 0.78 µm.
11 citations
TL;DR: In this article , a modified couple stress theory (MCST) and a mixed finite element method were used to develop a novel interface that can capture the microstructure-dependent size effect and be applied in the simulation of a PnC-based PEH device.
2 citations
TL;DR: In this paper , a constitutive model for shape memory alloys considering size effects is developed based on thermodynamic framework, which can be used for the analysis of structures having arbitrary shapes by being adopted into the finite element method.
1 citations
TL;DR: In this article , four-node quadrilateral and eight-node hexahedral elements are developed to simulate size effect based on strain gradient theory, and the displacement gradient field is approximated with linear polynomials and the coefficients are determined using the superconvergent patch recovery.
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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.
Abstract: Dislocation theory is used to invoke a strain gradient theory of rate independent plasticity. Hardening is assumed to result from the accumulation of both randomly stored and geometrically necessary dislocation. The density of the geometrically necessary dislocations scales with the gradient of plastic strain. A deformation theory of plasticity is introduced to represent in a phenomenological manner the relative roles of strain hardening and strain gradient hardening. The theory is a non-linear generalization of Cosserat couple stress theory. Tension and torsion experiments on thin copper wires confirm the presence of strain gradient hardening. The experiments are interpreted in the light of the new theory.
3,266 citations
TL;DR: HAL as discussed by the authors is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not, which may come from teaching and research institutions in France or abroad, or from public or private research centers.
Abstract: HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Elastic materials with couple-stresses R. Toupin
2,574 citations
TL;DR: In this paper, a new set of higher-order metrics is developed to characterize strain gradient behaviors in small-scale structures and a strain gradient elastic bending theory for plane-strain beams is developed.
Abstract: Conventional strain-based mechanics theory does not account for contributions from strain gradients. Failure to include strain gradient contributions can lead to underestimates of stresses and size-dependent behaviors in small-scale structures. In this paper, a new set of higher-order metrics is developed to characterize strain gradient behaviors. This set enables the application of the higher-order equilibrium conditions to strain gradient elasticity theory and reduces the number of independent elastic length scale parameters from five to three. On the basis of this new strain gradient theory, a strain gradient elastic bending theory for plane-strain beams is developed. Solutions for cantilever bending with a moment and line force applied at the free end are constructed based on the new higher-order bending theory. In classical bending theory, the normalized bending rigidity is independent of the length and thickness of the beam. In the solutions developed from the higher-order bending theory, the normalized higher-order bending rigidity has a new dependence on the thickness of the beam and on a higher-order bending parameter, bh. To determine the significance of the size dependence, we fabricated micron-sized beams and conducted bending tests using a nanoindenter. We found that the normalized beam rigidity exhibited an inverse squared dependence on the beam's thickness as predicted by the strain gradient elastic bending theory, and that the higher-order bending parameter, bh, is on the micron-scale. Potential errors from the experiments, model and fabrication were estimated and determined to be small relative to the observed increase in beam's bending rigidity. The present results indicate that the elastic strain gradient effect is significant in elastic deformation of small-scale structures.
2,466 citations
2,228 citations
TL;DR: In this article, a theory of non-local elasticity is presented via the vehicles of global balance laws and the second law of thermodynamics via the use of a localized Clausius-Duhem inequality and a variational statement of Gibbsian global thermodynamics.
2,201 citations