Pull In Characteristics Of Micro And Nano Structure Under Multi Field Coupling

There are many unique physical properties better mechanical and electrical coupling characteristics and lower energy consumption in Micro / nano electromechanical systems(M/NEMS).They have been used in micro and nano intelligent engineering in recent years.In the micro / nanoelectromechanical systems,pull in characteristics of micro and nano structure is the key component to the whole system,and it is significant to achieve the independent control,improve the automation and intelligent level of the system and enhance the reliability of the system.In this paper,we regarded the carbon nanotubes reinforced Euler Bernoulli nano-beam with clamped ends and axisymmetric circular nano-plate as the research objects and established the corresponding electromechanical coupling model by using continuum theory.And we studied and analyzed the pull-in characteristics of the models multi field coupling including thermal stress,Casimir force,surface effect,electric force.We used Fredholm integral equation and the method of separation of variables to investigate the pull-in characteristics of nano-beam and nano-plate,and the theoretical results of static pull-in displacements and static pull-in voltages were obtained.Besides,we utilized fifth-order Taylor expansion to study dynamic pull-in characteristics of axisymmetric circular nanoplate,and the numerical solution of the dynamic pull-in displacements and the pull-in voltages were obtained.The results show that carbon nanotubes can improve the structure stability,but CNTs reinforced structures are less stable due to the thermal stress induced by the temperature change;The influence of surface effect on pull-in characteristics of micro and nano structure is obvious,and the role of surface residual stress is dominant in this occasion.We also found that the bigger specific area of structure was,the more obvious the surface effect was;Dynamic pull-in voltages are about 90% of the static pull-in voltages,and the influence of thermal stress,surface effect and the Casimir force on the dynamic pull-in voltages are similar to the influence on the static pull-in voltages.The results of this paper will provide the relative theoretical basis for the better design and application of the micro and nano intelligent structure in the future.