In latest years small scale machining has been widely used in advanced engineering applications such as medical and optical devices, micro- nano-electro-mechanical systems. micromachining of metals, a depth cut becomes usually smaller than an average crystal size polycrystalline structure; thus, the cutting process zone can be localized fully indoors single grain. Due to crystallographic anisot...

We perform atomistic Monte Carlo simulations of bending a Lennard-Jones single crystal in two dimensions. Dislocations nucleate only at the free surface as there are no sources in the interior of the sample. When dislocations reach sufficient density, they spontaneously coalesce to nucleate grain boundaries, and the resulting microstructure depends strongly on the initial crystal orientation of...

Classical plasticity models, being scale independent, cannot capture any size depedent behavior. A remedy is to adopt a gradient plasticity model at the sub-granular (meso) scale to account for the different micro-processes leading to the various size effects. In this contribution, we adopt, at the meso scale, the isotropic gradient plasticity model in [1] which incorporated the plasticity rota...

We study the combined effects of grain size and texture on the strength of nanocrystalline copper (Cu) and nickel (Ni) using a crystal-plasticity based mechanics model. Within the model, slip occurs in discrete slip events exclusively by individual dislocations emitted statistically from the grain boundaries. We show that a Hall-Petch relationship emerges in both initially texture and non-textu...

Using a dislocations-based model of slip and crystal plasticity, we show by illustrative examples that the experimentally observed increase in the yield stress of very thin metallic membranes most likely is due to the variation of grain orientations through the thickness of the membrane, as well as the surface hardness due to oxidation or contamination, both of which generally are insignificant...

As an extension to strain-gradient models of size-dependent plastic behaviour, this work proposes a model for stress-gradient theory. The is distinguished from earlier works on the topic by its being embedded in thermodynamically consistent framework. development carried out context single-crystal plasticity, and draws conventional plasticity. explored numerically using example torsion thin wir...

The mechanisms of stress-assisted grain growth are explored using molecular dynamics simulations of nanoindentation in nanocrystalline Ni and Ni-1 at.% P as a function of grain size and deformation temperature. Grain coalescence is primarily confined to the high stress region beneath the simulated indentation zone in nanocrystalline Ni with a grain size of 3 nm. Grain orientation and atomic dis...

In this paper, a self-consistent plasticity theory is proposed to model the mechanical behaviours of irradiated face-centred cubic nanocrystalline metals. At the grain level, a tensorial crystal model with both irradiation and grain size effects is applied for the grain interior (GI), whereas both grain boundary (GB) sliding with irradiation effect and GB diffusion are considered in modelling t...

Gradient nano-grained (GNG) metals are a unique class of materials with spatial gradients in grain size, typically from the surface to the bulk. Here the gradient mechanical behavior inGNG copper is studied by a crystal plasticity finite elementmodel that accounts for grainsize-dependent yield strengths. The associated finite element simulations reveal both the gradient stress and gradient plas...