Viscoelastic Deformation Analysis To Tubular Dielectric Membrane Spring Actuator

Electroactive polymer?EAP?is a new type of flexible smart material developed in recent years and has become an important part of the research in the field of soft matter.EAP materials are mainly divided into ionic and electronic types according to their mechanism of action.Dielectric elastomer?DE?has excellent material properties due to their large strain,light weight,good flexibility,fast response and low cost.Therefore,the actuator,generator,artificial muscle and the like processed based on DE materials have great market value and application prospects.The mechanism of driving by the actuator made of DE material is:firstly,the surface of the DE material is uniformly coated with the flexible electrode,and then the dielectric elastomer is energized,and the thickness of the DE material is reduced under the applied electric field,and the surface area will be Increased,the dimensional deformation of the DE material is used to achieve the driving function and convert the electrical energy into mechanical energy.However,as a high molecular polymer material,DE material has significant viscoelastic properties.During the deformation process,its electrical and mechanical behavior has a significant dependence on the deformation time.At present,there are many researches on the elastic behavior of DE materials,and the research on its viscoelastic behavior is still in the ascendant.This paper studies the viscoelastic behavior of tubular dielectric membrane-spring actuator based on DE materials.The main research contents are as follows:?1?A tubular dielectric membrane-spring actuator consisting of a tubular dielectric membrane,a lightweight spring,and a rigid disk was constructed.Based on the principle of non-equilibrium thermodynamics,combined with the nonlinear dissipative theoretical model of dielectric elastomer,the tubular spring dielectric film driver is used as the research object,and the energy variation principle is used.The material model and the viscoelastic rheological model composed of spring and clay pot are selected to derive the state equation and kinematic equation for the deformation of the tubular spring dielectric actuator.The state equation and kinematic equation of the model is solved by the shooting method and the improved Euler method.Combined with the equation of motion of the viscoelastic rheological model,the variation of the physical variables considered with time and the variation of the profile deformation of the tubular dielectric membrane with time are obtained.The numerical simulation calculations show the force load type of the tubular dielectric membrane-spring actuator,and the spring stiffness has a significant influence on the viscoelastic force electrical behavior.A threshold value for the associated load when the tubular dielectric membrane-spring actuator is destabilized is also predicted.Different spring stiffness coefficients have significant influence on the contour deformation process of dielectric membrane.?2?The effects of the aspect ratio of the tubular dielectric membrane-spring actuator and the periodic force electrical load in the form of a sinusoidal function on the viscoelastic force behavior of the tubular dielectric membrane-spring actuator are discussed.Numerical simulation calculations show that the smaller the aspect ratio,the better the stability of the tubular spring dielectric membrane.Under the action of periodic force electric load in the form of sinusoidal function,the shear modulus of the dielectric membrane is gradually reduced due to the influence of viscoelasticity,and the longitudinal stretch ₁?and the longitudinal stress?₁ of the relevant physical quantities considered in numerical simulation calculation increase with the number of cycles.The results of this paper will help to understand the viscoelastic behavior of tubular dielectric membrane-spring actuator,and provide theoretical support for the optimal design of such dielectric membrane actuators.