Research On Shear Stress Characteristic Of MRF Base On Cylinder Model Under Complex Field

MRF is a new type smart material. It shows low viscosity Newton liquid without magnetic field. Once adding magnetic field, it responds with millisecond, and changes into solid or analogue solid. This character is named magetorhelogical effect. The MRF products generally are the applications of mechanical property of MRF at present. Therefor the research of MRF’s mechanical property is a important aspect of MRF study. Among many mechanical properties, shearing stress property is the widest used, and the study of MRF’s character is concentrate on it. The output of shearing stress property is mainly influenced by numbers factors such as magnetic field, temperature field, gravity field, shearing rate, shearing stress direction, the size shape or distribution of soft magnetic particles, runtime, the material or structure of device, surface roughness. Among those influence factors, magnetic field is the necessary element of magnetorhelogical effect. And in MRF’s practical work, a lot of mechanical energy translate into internal energy and cause the MRF’s temperature rise or temperature inhomogeneous distribution. In conclusion, magnetic field and temperature field is the most outstanding among all influence factors. MRF always works in the environment coupling magnetic field and temperature field.This paper briefly introduces the MRF and its main influence factor of mechanical characteristics. From the perspective of magnetic and temperature field, this paper summarizes the current situation and development tendency of the theory of MRF’s shear stress and the measurement technique of MRF’s characteristics. This paper analyses and compares the advantages and disadvantages of current theory and measurement technique of MRF. For the characteristics of MRF under compound field, this article put forwards its purpose significance, method of research.In the need of designing experimental facility and testing the characteristics of materials, the article summarize Bingham model, Double yield model, Herschel-Bulkley Model and Eyring Model to describe the characteristics of rheology of MRF. By comparison and analysis, Bingham model, which has less parameters and explicit physical meaning, has been chosen as the basic model of rheology theory of MRF under compound field. From the perspective of MRF’s working model, the article summarizes conduit model, plate shearing model, disk shearing model, cylinder shearing model. Cylinder shearing model has been chosen as the basic mechanic theory of experience device by comparing. Using finite element analysis, a force analysis of MRF’s element in cylinder model is made, and the mechanic model is obtained. The mechanic and kinematics law of MRF in cylinder model is analyzed and acquired. Finally, the article summarizes the measuring method of shearing stress and shearing velocity, which avoid the influence of pre-yield area in MRF’s measurement.From the respective of compound field, the article analyses the magnetic field and temperature field’s compound action on MRF practical application. Based on four perspectives which the article are analyses, the shearing stress output theory of MRF under compound field is obtained. With the theoretical derivation, we found that the essence of influence of temperature. The temperature has changed the permeability of soft-magnetic particle and the viscosity of carrier liquid, which has changed the magnetic field intensity of MRF and changed shearing stress output.Based on the analysis of shearing stress model, a set of devices which can be used to study the characteristics of MRF under compound field are developed. Using ANSYS software, the article simulates the distribution of temperature and magnetic field of the device. The simulation shows that the device offers an uniform distribute as well as stabilized compound field.The influence of magnetic field and shear rate experiment, and magnetic field and temperature field of composite measure experiment are designed, a large number of experimental data measured. From the perspective of experiment, the composite influence law of magnetic field and temperature field was studied in magnetorheological fluid shear work process. Data analysis showed that, magnetic rheological fluid shearing stress output rises as the field, shear rate increasing, and decreased with the increasing of temperature field. In comparison, the rising stress output intensity of the magnetic field is much greater than the influence of shear rate rise. The study also found that the magnetic field strength bigger, the shear stress with the rise and fall of the temperature field are larger. It consistent with the rules that when the magnetic field increases, the temperature rise in the influence of magnetic field greater. Analysis of the experimental data show that, the theory that transfer the impact of temperature field into the influence of magnetic field and viscosity by Curie formula, viscosity temperature characteristics of the formula is in good agreement with the actual, which proves the correctness of the theory.Based on the magnetic field and the temperature field theoretical model, the temperature field compensation experiment is designed. Through the micro rise of magnetic field, the Magnetorheological fluid shear stress dropping is compensated, which impact by the rise temperature field. Through the experiment, the magnetorheological fluid shear stress decrease was reduced from 30%/100℃ to 3%/100℃, down to an acceptable range. It proved the correctness of magnetic field and temperature field complexly impact on magnetorheological fluid affect theory.