Study On Mechanical Behavior Of Self-sustained Rolling Of A Responsive Rod

In recent years,smart materials have not only become the subject of extensive academic research,but also have been promoted widely as a key technology,widely used in industry,aerospace,medicine,modern architecture and other fields.It has been found that some properties of intelligent materials can produce special intelligent behaviors such as self-sensing,self-healing,self-actuating,self-diagnostic and shape changing under the action of external stimulation when they are used in some special systems.These intelligent behaviors may become the basis of new products with unique functions in the future,which is of positive significance to the discovery of new technologies and the realization of scientific and technological innovation.The realization of intelligent behavior depends on the material properties and the external systems that respond to the material properties.The realization of intelligent behavior depends more on the design of external systems responding to material properties than material properties.Among many external systems,the self-excited vibration system has gained the favor and attention of a large number of scholars and experts because of its advantages of self-sustaining,autonomous movement and no need for external control.Various devices based on the self-excited vibration system have been designed.However,the design and research of various self-excited vibration systems are mostly concentrated in the experimental field,and the theoretical modeling is very scarce.Therefore,the internal motion mechanism and principle of most self-excited vibration systems can not be reasonably explained,which limits the application of these self-excited vibration systems in traditional industries and new technology fields.In this paper,the newly discovered self-excited vibration mode of the rolling rod on the platform is theoretically modeled and studied.First of all,taking the self-excited vibration system of ordinary elastic rod and viscoelastic rod in rolling motion mode under thermal stimulation as the research object,based on the heat conduction and viscoelasticity theory,the rolling theoretical models of thermal responsive elastic and viscoelastic rods are established.By analyzing the temperature field,thermal moment,transverse bending curvature,deformation and velocity of the rod under stable rolling state,the rolling behavior of elastic and viscoelastic rods under thermal stimulation is simulated.Then,taking the self-excited vibration system of azobenzene liquid crystal elastomer rod in rolling motion mode under light stimulation as the research object,based on the theory of photo-induced deformation and photo-mechanical effect,the rolling theoretical model of photo-responsive azobenzene liquid crystal elastomer rod is established.The rolling behavior of azobenzene liquid crystal elastomer rod under different light angles was simulated by analyzing the number fraction of the photochromic liquid crystal molecules in cis state,transverse bending curvature,out-of-plane moment and velocity.The research work of this paper is as follows:(1)The rolling velocity of thermal and light responsive rods on the platform is studied.There are two stable states of the thermal and optical responsive rods while rolling on the platform,which are called the phenomenon of bistable state of the velocity.The difference is that the thermally responsive rod must be pushed to trigger rolling,while the photo-responsive rod can roll autonomously as the light angle increases.However,when the light angle is increased to 90 degrees(i.e.,parallel lighting),the rod never rolls.(2)The universal effective driving moment formula of the rod under the condition of stable rolling on the hot platform is obtained.Based on the long-rod hypothesis,the effective driving moment of both thermally responsive elastic and viscoelastic rods is the product of the transverse bending curvature and the out-of-plane bending moment,and the transverse bending curvature of the rods is determined by the rod itself during rolling.(3)The relationship between rolling velocity and viscosity of thermally responsive viscoelastic rod is studied.The results show that the rolling velocity of the thermally responsive viscoelastic rod is strongly related to the viscosity,and the effect of the material viscosity is most significant when the characteristic time scale related to the viscoelastic material is equivalent to the time scale of the rod rolling(i.e.,η1～).The results reveal the internal motion mechanism and principle of the self-excited vibration system of the rod in rolling mode induced by thermal and light stimulation,which is an effective supplement to the self-excited vibration system theory which is relatively lacking at present,and provides sufficient theoretical guidance and support for the future application of this new self-excited vibration mode.Figure[33]table[1]reference[83]...