Simulation On Dynamics Properties Of Rotary-Oscillatory Devices From Curved Carbon Nanotubes

Carbon nanotubes are potential candidate material in design of such nanodevices as nanobearing,nano oscillator,nanomotor,etc,due to their super high flexibility and inter-shell superlubrication.Up to now,rotary-oscillatory properties of multi-walled carbon nanotubes attracts much attention and lots of related work were published to reveal the properties of straight CNTs.In this dissertation,the rotary-oscillatory properties of curved double-walled CNTs(DWNTs)were investigated systematically by molecular dynamics simulations,and following results,which will guide the related design,are obtained:(1)The histories rotation and oscillation of an inner tube having high initial rotational frequency in a curved outer tube were investigated by putting the curved DWNTs at the microcanonical NVE ensemble.It is found that both rotation and oscillation of the inner tube damp quickly.The damping rate increases with the increase of the curvature of outer tube(stator);(2)We provide the conceptual design of a nano universal joint from curved DWNTs.The rotation transmission system has a deformable stator.As the curvature of stator changes,the output rotation of the rotor(inner tube)will be different from that of the nanomotor which provides input rotation on the rotor.As changing the configuration of the adjacent ends of nanomotor and rotor,not only the rotational direction but also the frequency of the rotor are different from those of nanomotor.Hence,the system can provide both the same and different output rotation of the rotor as comparing the input rotation;(3)In studying the output rotation of a curved rotor,we find that the in-plane vibration of the middle part of the rotor may become serious.It can be considered as resonance of the rotor during rotation.Due to large amplitude vibration,the free end of the rotor shows oscillation with large amplitude,too.It is found that the amplitude depends on the difference between the input rotational frequency and the natural frequency of the system,i.e.,lower difference leads to higher amplitude.Hence,the system can provide not only different rotation but also oscillation of rotor.The system,therefore,can be considered as a system with multiple output system;(4)We design an over-speeding rotation transmission system,in which the rotational frequency of rotor is greater than that of input rotation.Results show that only when the radius of the rotor is lower than that of the nanomotor,the over-speeding state may appear.Besides,the ratio between the output and input rotational frequencies is not higher than that between the radii of the rotor and nanomotor.The rotation transmissions state can be adjusted by changing such factors as environmental temperature,input rotation,curvature of rotor,configuration of the adjacent ends of rotor and nanomotor,etc.