Experimental Research On Circle-trough MR Braking Performance

Magneto-rheological(MR)fluid is a new type of intelligent materials.The rheological properties of MR fluid are reversibly changed by the application of an external magnetic field.The controllable MR effect of MR fluid has aroused highly attention by overseas and domestic learners.Based on the projects of the Natural Science Foundation of China “Mechanism and application of MR fluid transmission drove by SMA under thermal effect(51175532)”,the structure and parameters of magnetic circuit of circle-trough type MR braking device were designed.The braking performance was studied by ANSYS simulation analysis and experimental testing.The main work in this dissertation is as follows:1)The composition and preparation as well as the three characteristics of MR fluid are presented and introduced.The rheological property when MR fluid exposed to an external magnetic field has been analyzed based on the three constitutive models.2)The working principle of the disc type MR braking device has been researched as well as the model of braking torque.Based on Bingham model,the braking torque equation is derived by utilizing the differential element method.According to the requirement of braking torque,the design of structure and magnetic circuit is completed,which is verified by the method of ANSYS simulation.3)The operation principle of the cylindrical type MR braking device has been researched as well as the model of braking torque,and the braking torque equation is derived by means of Bingham model.According to the requirement of braking torque,the design of structure and magnetic circuit is completed,which is also verified by the method of ANSYS simulation.4)The simulation results of the disc type and cylindrical type MR braking system show that the braking performance of the disc type is better than the cylindrical type,which is the significance of the research on circle-trough type MR braking device.5)The work principle of circle-trough type MR braking device is analyzed.Based on the rheological properties of ring groove,combined with the yield stress model of MR fluid in the action of shear,the equation of braking torque is established.The relationships of magnetic field strength with braking time and braking torque are analyzed.The study for quantitative analysis of three major factors is completed,which directly affect the braking performance.The basic geometric parameters and magnetic circuit of circle-trough type MR braking device are obtained.The design rationality of braking device is determined through ANSYS simulation.6)The relationship of magnetic flux density and braking torque is obtained by experiment.The errors between experimental results and theoretical values are analyzed.The curves of shear stress with magnetic flux density,temperature and shear rate are experimentally measured.