Research On MRF Shear Characteristics Of The Non-uniform Magnetic Field And Temperature Composite Field

Magnetorheological fluid(MRF)is an important branch of the intelligent materials. In the absence of magnetic field, MRF is suspended Newton fluid, when the external magnetic field exists, MRF can turns into the sticky solid or solid structure in milliseconds, the reversible transformation is called the MRF effect.The MR devices is developed based on the MRF effect, in which the MRF shear stress in the MR devices are widely used. MRF shear stress is mainly influenced by numbers factors such as magnetic field, temperature, 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 and so on. MRF devices cannot do without producing heat and then change the work temperature, which leads the MR devices to working in the coupling environment of the magnetic field and temperature.At present the MR devices is mostly based on a static uniform magnetic field MRF shear stress model, do not study on the change of magnetic field and temperature, which leads to device failure. Having imitated the device failure environment, it researched on the effects of the MRF shear by the non-uniform magnetic field and temperature composite field.It introduced MRF and its characteristics, analysising the MRF research status at home and abroad and the pros and cons of the shear stress measurement devices, mainly explained the failure of the static magnetic field of MRF shear model from the angle of magnetic field and temperature. It put forward the researching methods to complete researching on MRF shear stress under the non-uniform magnetic field and temperature composite field, to provide a reference for the design and application of MR device. The main works is as follows:(1) Established the MRF shear stress microscopic model under the action of non-uniform magnetic field. Considering the effects of the non-uniform magnetic field and temperature on the interaction between the magnetic dipoles, it pointed out that the temperature changes the action play a secondary role between magnetic dipole interactions. While the magnetic field changes the magnetic dipole magnetization is the decisive role of the interaction. The non-uniform magnetic field is very complex, and the finite element idea is used to divide the whole non-uniform magnetic field space. Each grid is uniform magnetic field,according to the ampere molecular current hypothesis to obtain a uniform magnetic field of magnetic dipole interaction theory formula, and then the shear stress of non-uniform magnetic field shear stress formula is obtained by integrating the uniform magnetic field, to get the MRF shear stress influence factors.(2) Developed a non-uniform magnetic field and temperature composite field MRF shear stress measurement device, which mainly includes the non-uniform magnetic and temperature composite field device, cutting device, mechanical movement module and data acquisitionand processing module. Having selected the Czochralski method to measure the shear stress,built an non-uniform magnetic field and temperature of generating devicethe by the coupling way, assisted by ANSYS simulation to adjust the shearing direction of the MRF shear device,debugged the program to realize the automatic measurement of shear, it completed the overall design of the whole measuring device.(3) Completed the description of the non-uniform magnetic field and temperature composite field environment. In the experiment, the temperature of magneto rheological fluid are equal everywhere at the same time, therefore need to compare the influence of temperature on MRF shear stress by the longitudinal comparison. In the experimental area,the spatial distribution of magnetic induction intensity by the two C type electromagnet is not the superposition of a simple single electromagnet magnetic field, it need the law of magnetic circuit, ANSYS simulation and measurements to get an accurately describe of the non-uniform magnetic field spatial distribution of magnetic induction intensity.(4) Completed the measurement the MRF shear stress of the non-uniform magnetic field and temperature, and analyzed the experimental data: the same magnetic field distribution, the differences between MRF shear stress measurements of composite field and the theoretical value of the uniform magnetic field shear stress model shows that the uniform magnetic field theory is fail under the coupling field. Under the same temperature, the magnetic field of magneto rheological fluid shear stress increases with the increasing of the magnetic induction intensity. Under the same magnetic induction intensity, the shear stress decreased with the increasing of temperature. The greater the magnetic induction intensity field is, the greater the influence of temperature-rise on the magnetic and shear stress is. In comparison, the influence of the rise of the magnetic induction intensity is greater than the temperature rise on shear stress. The research did not only verify the accuracy of the experimental device and measurement results, and also analysis the cause of the differences.It simulated the working environment of magneto rheological devices, studied the failure mechanism of magnetorheological devices due to the change of temperature and magnetic field, providing some guidance for design and development of MR devices.