Z. Shafiei, S. Sarrami-Foroushani, M. Azhari,
Volume 38, Issue 2 (2-2020)
Abstract
Graphene is one of the nanostructured materials that has recently attracted the attention of many researchers. This is due to the increasing expansion of nanotechnology and the application of this nanostructure in technology and industry owing to its mechanical, electrical and thermal properties. Thermal buckling behavior of single-layered graphene sheets is studied in this paper. Given the failure of classical theories to consider the scale effects and the limitations of the nano-sized experimental investigations of nano-materials, the small-scale effect is taken into account in this study, by employing the modified couple stress theory which has only one scale parameter. On the other hand, the two-variable refined plate theory, which considers the shear deformations in addition to bending deformations, is used to define the displacement field and to formulate the problem. The developed finite strip method formulation is used to evaluate the critical buckling temperature of the nanoplates. The validity of the proposed method is confirmed by comparing the results of this study with the those in the literature. The effects of different boundary conditions, temperature changing patterns, aspect ratio, and the ratio of length parameter to thickness on the critical buckling temperature are considered and the results are presented in the form of Tables and Figures
A. M. Salehizadeh, A. Shafiei,
Volume 38, Issue 2 (2-2020)
Abstract
This paper presents a numerical analysis of granular column collapse phenomenon using a two-dimensional smoothed particle hydrodynamics model and a local constitutive law proposed by Jop et al. This constitutive law, which is based on the viscoplastic behaviour of dense granular material flows, is characterized by an apparent viscosity depending both on the local strain rate and the local pressure. The rheological parameters are directly derived from the experiments. A simple proposed regularization method used in the viscosity relation to reproduce the stopping condition and the free surface of a granular flow where the pressure is disappeared. Pressure oscillation, as the main disadvantage of the weakly compressible SPH method, leads to an inaccurate pressure distribution. In this research, a new algorithm is proposed to remove the nonphysical oscillations by relating the divergence of velocity to the Laplacian of pressure. The simulations based on the proposed SPH algorithm satisfactorily capture the dynamics of gravity-driven granular flows observed in the experiments. The maximum thickness of a granular flowing on a rough inclined plane is obtained based on the local rheology model and compared with the experimental results. The run-out distances and the slopes of the deposits in the simulations showed a good agreement with the values found in the experiments. The results of the simulation proved that the initial column ratio played an important role in spreading the granular mass
