Interlayer shear effect on vibrational behavior of bilayer graphene using the molecular mechanics simulation

In this article,the interlayer shear effects on vibrational behavior of bilayer graphene(BG)are studied by using the molecular mechanics(MM)simulation.Investigation on mechanical behavior of graphenes has recently attracted because of their excellent properties.MM simulation is exploited for modeling of covalent bond in the plane of graphene layers and they are modeled as space-frame structures.The interaction between two layers is modeled by Lennard–Jones potential for not only two apposite atoms but also for all adjacent atoms.The frequencies and mode shapes for cantilever and bridged bilayer graphene as well as monolayer graphene(MG)are obtained by a finite element approach.Results show that the interlayer shear interaction has considerable effect on vibrational behavior of BG and increases the natural frequencies,because existence of horizontal forces(shear forces)that prevent the lateral displacements.It can be seen that the interaction between two layers are more considerable in second mode because the curvature and variation of displacement are higher in second mode.Also it can be found that changing of mode shapes has considerable effect on shear interaction.

Vibration behavior optimization of planetary gear sets

This paper presents a global optimization method focused on planetary gear vibration reduction by means of tip relief profile modifications.A nonlinear dynamic model is uspd to study the vibration behavior.In order to investig ate the optimal radius and amplitude,Brute Force method optimization is used.One approach in optimization is straightforward and requires considerable computation power:brute force methods try to calculate all possible solutions and decide afterwards which one is the best.Results show the influence of optimal profile on planetary gear vibrations.

Nonlinear vibration analysis of a rotor supported by magnetic bearings using homotopy perturbation method

In this paper,the effects of nonlinear forces due to the electromagnetic field of bearing and the unbalancing force on nonlinear vibration behavior of a rotor is investigated.The rotor is modeled as a rigid body that is supported by two magnetic bearings with eightpolar structures.The governing dynamics equations of the system that are coupled nonlinear second order ordinary differential equations(ODEs)are derived,and for solving these equations,the homotopy perturbation method(HPM)is used.By applying HPM,the possibility of presenting a harmonic semi-analytical solution,is provided.In fact,with equality the coefficient of auxiliary parameter(p),the system of coupled nonlinear second order and non-homogenous differential equations are obtained so that consists of unbalancing effects.By considering some initial condition for displacement and velocity in the horizontal and vertical directions,free vibration analysis is done and next,the forced vibration analysis under the effect of harmonic forces also is investigated.Likewise,various parameters on the vibration behavior of rotor are studied.Changes in amplitude and response phase per excitation frequency are investigated.Results show that by increasing excitation frequency,the motion amplitude is also increases and by passing the critical speed,it decreases.Also it shows that the magnetic bearing system performance is in stable maintenance of rotor.The parameters affecting on vibration behavior,has been studied and by comparison the results with the other references,which have a good precision up to 2nd order of embedding parameter,it implies the accuracy of this method in current research.