Journal of Simulation and Analysis of Novel Technologies in Mechanical Engineering
Volume:10 Issue: 3, Aug 2017

The dynamic instability of single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT) and triple-walled carbon nanotubes (TWCNT) embedded in an elastic medium under combined static and periodic axial loads are investigated using Floquet–Lyapunov theory. An elastic multiple-beam model is utilized where the nested slender nanotubes are coupled with each other through the van der Waals (vdW) interlayer interaction. Moreover, a radius-dependent vdW interaction coefficient accounting for the contribution of the vdW interactions between adjacent and non-adjacent layers is considered. The Galerkin’s approximate method on the basis of trigonometric mode shape functions is used to reduce the coupled governing partial differential equations to a system of extended Mathieu-Hill equations. Applying Floquet–Lyapunov theory, the effects of elastic medium, length, number of layers and exciting frequencies on the instability conditions of CNTs are investigated. Results show that elastic medium, length of CNTs, number of layer and exciting frequency have significant effect on instability conditions of multi-walled CNTs.

AISI 301 stainless steel is a frequently used metal, especially in high temperature demands and or in part with high corrosion risk. Thin spring steel plates can be used as expansions of heat furnaces insulation and variety of all other springs. The present study has assessed the effects of temperature and thermal treatment time span on the microstructure of stainless steel 301 to achieve elasticity and found out that microstructure gets smaller. As well as the Martensitic ά phase in the sample distributes uniformly after thermal treatment at 450 ºC for 20 minutes then water quenched in 10 ºC. By using X-ray diffraction, it can be found that the reduction in crystalline size of the Martensite ά and increasing in Martensite volume fraction is the cause of the elasticity of the samples. All obtained results confirmed by Ferittscope test.

The structural analysis of an infinite unsymmetric laminated composite Timoshenko beam over Pasternak viscoelastic foundation under moving load is studied. The beam is subjected to a travelling concentrated load. Closed form steady state solutions, based on the first-order shear deformation theory (FSDT) are developed. In this analysis, the effect of bend-twist coupling is also evaluated. Selecting of an appropriate displacement field for deflection of the composite beam and using the principle of total minimum potential energy, the governing differential equations of motion are obtained and solved using complex infinite Fourier transformation method. The dynamic response of unsymmetric angle-ply laminated beam under moving load has been compared with existing results in the literature and a very good agreement is observed. The results for variation of the deflection, bending moment, shear force and bending stress are presented. In addition, the influences of the stiffness, shear layer viscosity of foundation, velocity of the moving load and also different thicknesses of the beam on the structural response are studied.

This paper presents a model-based control design for trajectory tracking of two-wheeled mobile robots based on Linear Quadratic Regulator (LQR) optimal control. The model proposed in this article has been implemented on a computational model which is obtained from kinematic and dynamic relations of KHEPERA IV. The purpose of control is to track a predefined reference trajectory with the best possible precision considering the dynamic limits of the robot. Applying several challenging paths to the system showed that the control design is able to track applied reference paths with an acceptable tracking error.

In this paper, free vibration analysis and forced vibration analysis of FG doubly clamped micro-beams is studied based on the third order shear deformation and modified couple stress theories. The size dependent dynamic equilibrium equations and both the classical and non-classical boundary conditions are derived using a variational approach. It is assumed that all properties of the FG micro-beam follow a power law form through thickness. The motion equations are solved by employing Furrier series in conjunction with Galerkin method. Also, effects of aspect ratio, power index and dimensionless length scale parameter on the natural frequencies and amplitude-excite frequency curves are investigated. Findings indicate that dimensionless frequencies are strongly dependent on the values of the material length scale parameter and power index. The numerical results of this study indicate that if the thickness of the beam is in the order of the material length scale parameter, size effects are more significant.

In this paper, an experimental study has been conducted on the rheological behavior of Water (80%) and Ethylene-glycol (20%) in presence of Al2O3-MWCNTs hybrid nanomaterials. For this purpose, nanofluid samples were prepared by suspending the nanomaterials in a mixture of water and EG with solid volume fractions of 0.0625%, 0.125%, 0.25% and 0.5% Viscosity measurements were performed at various shear rates and in the temperatures range of 25 to 50⁰C. Experimental data showed that all hybrid nanofluid samples had Newtonian behavior. also Results showed that nanofluid viscosity decreased with increasing temperature and augmented with increasing the volume fraction. Eventually, a new accurate correlation was developed to assist the calculation of the viscosity of the Al2O3-MWCNTs/water-EG at different temperatures and volume fractions.