Study On The Vibration Characteristics Of Functionally Graded Fluid-conveying Microtubes Based On The Theory Of Higher Order Continuum Mechanics

With the development of microelectronics technology,fluid-conveying microtubes are gradually becoming the core components of micro-electro-mechanical systems.As an important part of micro-electro-mechanical systems,the dynamic characteristics of the fluid-conveying mic.rotubes is very important to the safe operation of the whole micro-electro-mechanical systems.Therefore,it is one of the key scientific problems to be solved in the design and application of micro-electromechanical systems to accurately grasp the vibration mechanism of the fluid-conveying microtubes.Functionally graded material is a kind of new composite material,which composed of two or more kinds of constituent phases.Its component phases,microstructure and material mechanical properties have the characteristics of continuous change.In engineering applications,material mechanical properties can be designed according to the needs.Therefore,based on the theory of higher-order continuum mechanics,a fluid-conveying microtube composed of functionally graded materials is proposed as the research object in this paper,and the differential equation of the motion of functionally graded fluid-conveying microlubes is established by Hamilton principle.Through numerical analysis methods,the effects of functionally graded materials,microscale parameters,mass ratio,excitation loads,fluid velocity and other physical parameters on the vibration characteristics of functionally graded fluid-conveying microtubes are studied.The main research contents of this paper are as follows:(1)The differential equation of free vibration motion of ffinctional gradient fluid-conveying microtube is established.1 he effects of functionally graded materials,microscale parameters,mass ratio and fluid velocity on the free vibration characteristics of functionally graded fluid-conveying microtube are investigated by numerical analysis.T he results show that the larger the volume fraction power law index and fluid velocity is,the worse the stability of the fluid-conveying microtube is.The smaller the microscale parameters and the larger the mass ratio,the better the stability of the fluid-conveying microtube.(2)The vibration characteristics of functional gradient fluid-conveying microtube under multiple physical fields coupling are studied.Considering the coupling effects of temperature,magnetic field and elastic medium stiffness,the effects of temperature,magnetic field strength and elastic medium stiffness on the vibration characteristics of functionally gradient fluid-conveying microtube are analyzed.The results show that the higher the temperature,the worse the stability of the fluid-conveying microtube,the more unstable.The larger the magnetic field intensity and elastic medium stiffness,the better the stability of the fluid-conveying microtube.(3)The nonlinear motion differential equations of functionally gradient simply supported fluidconveying microtubes under excitation loads are constructed.The nonlinear motion differential equations were solved by Runge-Kutta method.The effect of excitation loads on nonlinear vibration characteristics of simply supported fluid-conveying microtube is analyzed by phase diagram,bifurcation diagram and time history diagram.The results show that the vibration displacement is proportional to the amplitude of the excitation loads when the simply supported fluid-conveying microtube is in steady state.When the simply supported fluid-conveying microtube is unstable,the amplitude effect of excitation loads is almost negligible,but the larger the frequency of excitation loads,the larger the vibration displacement.(4)The nonlinear vibration of functionally graded simply supported fluid-conveying microtube in pulsating internal flow is studied.Considering the pulsation of fluid velocity,the nonlinear motion differential equation of functionally graded simply supported fluid-conveying microtube is established.The effect of fluid pulsation on the nonlinear vibration characteristics of simply supported fluid-conveying microtube is analyzed by phase diagram,bifurcation diagram and power spectrum diagram.The results show that the motion pattern of simply supported fluid-conveying microtube changes from quasi periodic to chaotic with the increase of fluid velocity.The greater the amplitude of fluid pulsation,the worse the stability.Reducing the amplitude of fluid pulsation can improve the stability.