Research On Dissipation Characteristics Of Nanoresonators Based On Generalized Thermoelasticity

Micro-nano resonators have attracted much attention in many fields such as high-precision measurement and signal processing,and have become one of the current research priorities and hotspots.During the vibration process,uneven deformation occurs inside the resonator,the temperature of the pressed region increases,and the temperature of the stretched region decreases,so that the temperature difference causes the irreversible heat flow to diffuse from the high temperature region to the low temperature region.Thermoelastic damping is the energy dissipation caused by the irreversibility of thermal conduction and is one of the main energy dissipation mechanisms of resonators.In order to improve the working efficiency of micro-nano resonators and reduce energy dissipation,it is urgent to study the mechanism of energy dissipation of resonators.In this paper,based on the non-negligible surface effect of the resonator at small scale and the limitations of classical heat conduction theory and objective inconsistency,the thermoelastic damping of micro-nano resonators is studied.The main work is as follows:(1)The effect of surface effect on the thermoelastic damping of the resonator is studied based on the classical Fourier heat conduction theory.Due to its small size,nano-devices have a more pronounced effect on surface atoms,and surface atoms are significantly different in physical properties than internal atoms.Surface effects have also become a very important factor affecting nanostructured materials.This chapter gives the governing equations considering surface effects based on the Hamilton principle and the principle of minimum potential of thermal flow,and solves the expression of thermoelastic damping.The results show that the effect of surface effect on thermoelastic damping is obvious at the micro-nano scale,and it will affect the peak of thermoelastic damping.(2)The effect of surface generalized thermoelastic theory on the thermoelastic damping of resonators is studied based on the non-Fourier heat conduction theory.The classical Fourier theory holds that the heat propagation velocity is infinite,which is inconsistent with the objective facts;therefore,this chapter considers the influence of the generalized thermoelastic theory of heat propagation velocity finiteness on the thermoelastic damping.Studies have shown that for the longitudinal vibration considering the generalized thermoelastic theory,the thermoelastic damping is larger than the peak of the generalized thermoelastic theoretical damping,and the position of the peak is shifted.(3)Based on the surface generalized thermoelastic theory and the relaxation time between temperature increment and thermal expansion,the influence of the thermal vibration damping on the transverse vibration of the resonator beam is discussed.The results show that the surface effect and generalized thermoelastic theory have great influence on the thermoelasticity at the micro-nano scale,and the results based on the generalized thermoelastic theory are far greater than the peaks of the thermoelastic damping based on the LR model;at the same time,the nanobeams The width and initial temperature also have a certain effect on the thermoelastic damping.Finally,the results of lateral vibration show that it has the same mechanism as the thermoelastic damping in the longitudinal vibration mode.In this paper,the effects of surface effects and generalized thermoelasticity on the thermoelastic damping of micro/nano resonators are discussed.The results can provide reference for the sensitivity and efficiency of micro-nano resonator components.