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Vibrational analysis of armchair phosphorene nanotubes by a DFT-based finite element model

Rouhi S., Shahnazari A., Ansari R.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 2

611--621

EN

A finite element model based upon the density functional theory is developed to investigate the vibrational characteristics of armchair phosphorene nanotubes. To this end, the PP bonds are simulated by beam elements whose elastic properties are obtained from the analogy of molecular and structural mechanics. The effects of nanotube length, diameter and boundary conditions on the frequencies of armchair phosphorene nanotubes are evaluated. It is shown that the effect of nanotube radius on its natural frequency is weakened by increasing the nanotube aspect ratio. Comparing the first ten frequencies of armchair phosphorene nanotubes with different diameters, it is observed that the effect of diameter on the vibrational behavior of phosphorene nanotubes is more pronounced at higher modes.

2

Effects of multi-pass FSP on the β phase (Mg17Al12) distribution and mechanical properties of AZ91C magnesium alloy

Rouhi S., Dadashpour M., Mostafapour A., Doniavi A.

Journal of Achievements in Materials and Manufacturing Engineering

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2017

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Vol. 82, nr 2

77--85

EN

Purpose: The principle and advantages of friction stir processing (FSP) for the production of a highly formable Mg alloy, and some convincing experimental results are reported in this paper. The aim is to understand the relationship between the microstructure characteristics and the mechanical properties behaviour of the number of FSP passes AZ91C alloy. Design/methodology/approach: FSP is a solid state processing technique which involves plunging and traversing a square pin profiles FSP tool through the material. In this study, a fine-grained multi-phase AZ91C magnesium alloy was produced by applying FSP on as-cast AZ91C alloy. Findings: FSP achieved grain refinement and homogenization of the as-cast microstructure in Mg alloy AZ91C. FSP produced a fine homogeneous microstructure having a grain size of 6 μm throughout the plate. Also tensile properties of the specimen produced in one, two and three passes were investigated by standard tensile test. Results show that FSP improved the tensile characteristics of the as cast AZ91C alloy significantly. As the number of passes increased, higher UTS and TE were achieved due to finer grains and more dissolution of β phase (Mg17Al12). Originality/value: The present study shows that FSP is an efficient production method for a large-scale plate of a highly formable Mg alloy.

3

Stability characteristics of single-walled boron nitride nanotubes

Ansari R., Rouhi S., Mirnezhad M., Aryayi M.

Archives of Civil and Mechanical Engineering

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2015

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Vol. 15, no. 1

162--170

EN

Boron nitride nanotubes, like carbon nanotubes, possess extraordinary mechanical properties. Herein, a three-dimensional finite element model is proposed in which the nanotubes are modeled using the principles of structural mechanics. To obtain the properties of this model, a linkage between the molecular mechanics and the density functional theory is constructed. The model is utilized to study the buckling behavior of single-walled boron nitride nanotubes with different geometries and boundary conditions. It is shown that at the same radius, longer nanotubes are less stable. However, for sufficiently long nanotubes the effect of side length decreases.