Research On Transmission Performance Of Electrothermal Shape Memory Alloy Spring And Magnetorheological Fluid

Shape memory alloys and magnetorheological fluids,typical smart materials,have broad application prospects in aerospace,bridge construction,biomedicine,automotive industry and other fields due to their unique mechanical properties.In this paper,a method and transmission device of combined transmission of electrothermal shape memory alloy spring and magnetorheological fluid based on shape memory effect and magnetorheological effect are proposed to address the defects of magnetorheological fluid that decay or even fail under high temperature.The combined transmission process and the transmission mechanism were analyzed,the selection of the combined transmission configuration and the design of key dimensions were studied,and the parameters of the magnetic field performance and transmission performance of the combined transmission were quantitatively analyzed by combining theoretical analysis and experimental research such as the finite element method.It aims to provide a theoretical basis for the design and manufacture of intelligent transmission devices with stable hightemperature transmission performance and multi-physical layer sensing capabilities such as temperature field,electric field and magnetic field.It is expected to provide a new idea for the design and research of combined shape memory alloy and magnetorheological fluid transmission in the field of intelligent transmission.The main research works in the full paper are as follows.(1)The unique shape memory effect and superelastic mechanical properties of shape memory alloys were introduced,and the process and mechanism of action of the shape memory effect and superelasticity were described;the composition of magnetorheological fluid materials was introduced,and the mechanism of magnetorheological effect generated by magnetorheological fluid and the basic working mode of magnetorheological fluid were elaborated.(2)Based on the pure shear constitutive model of shape memory alloy,the deformation equation of electrothermal shape memory alloy helical spring was derived,and the thermodynamic equation of electrothermal shape memory alloy helical spring was derived based on the heat balance equation to obtain the thermomechanical characteristics of electrothermal shape memory alloy helical spring drive;the basic structure and drive performance of three types of typical magnetorheological fluid drives were analyzed,and the geometry size of magnetorheological fluid working gap,magnetorheological fluid volume were used as design variables to obtain the drive performance of magnetorheological fluid drives of different configurations.The basic structure and drive performance of three types of typical magnetorheological fluid drives were analyzed,and the drive performance of different configurations of magnetorheological fluid drives was obtained by taking the geometry of the magnetorheological fluid working gap and the volume of magnetorheological fluid as design variables;the design of the drive structure and magnetic field was carried out according to the drive performance design values,and the influence of parameters such as the size of the drive structure and the size,current and number of turns of the excitation coil on the drive performance was obtained.(3)Based on the finite element method,simulation and analysis of the whole process of shape memory effect of electrothermal shape memory alloy springs were carried out.The force-driven,displacement-driven and force-displacement-driven characteristics of electrothermal shape memory alloy springs were analyzed according to the load and constraint conditions,and the results of finite element analysis of the thermomechanical properties of electrothermal shape memory alloy springs were basically consistent with the theoretical values.(4)The magnetic field distribution law of the combined transmission device of electrothermal shape memory alloy spring and magnetorheological fluid was derived by the finite element method;the thermal field finite element analysis of the transmission device was carried out by combining the heat load and heat conduction boundary conditions,and the influence of the heat generation of the transmission device on the electrothermal shape memory alloy spring during the transmission process was discussed to derive the combined transmission performance,and the influence of the magnetorheological fluid gap size,current,coil arrangement and current direction of each coil on the transmission performance of the transmission device was quantitatively analyzed.(5)The effects of the microscopic body-centered tetragonal structure of the magnetorheological fluid on the equivalent permeability of the magnetorheological fluid were analyzed.The magnetic and mechanical properties of magnetorheological fluids with different volume fractions were investigated,and the effects of temperature,volume fraction,permeability and coil current on the transmission performance of a variable volume fraction magnetorheological fluid drive driven by an electrothermal shape memory alloy spring were derived.(6)A complete experimental analysis of the thermo-mechanical properties of the electrothermal shape memory alloy spiral spring was carried out by the constructed experimental device,and the combined transmission performance of the shape memory alloy spring and magnetorheological fluid was tested by the constructed transmission test system,comparing the theoretical analysis results with the experimental test results to verify the theoretical correctness of this paper in the design and analysis process.The innovations of this paper are as follows.(1)Based on the pure shear constitution model of shape memory alloy and the thermal equilibrium equation of electrothermal shape memory alloy spring,a theoretical model of thermal drive of electrothermal shape memory alloy spiral spring is established,which provides a theoretical basis for the design and manufacture of new shape memory alloy actuators.(2)Based on the shape memory effect and magnetorheological fluid effect,the combined drive equation of electrothermal shape memory alloy spring and magnetorheological fluid was established,and the mechanism of the combined drive equation was revealed,which provides a new idea and method to solve the performance degradation of magnetorheological fluid at high temperature.(3)Based on the thermal driving characteristics of shape memory alloy,the equivalent permeability model and shear yield stress equation of magnetorheological fluid were established,and the relationship between the volume fraction of magnetic particles and the equivalent permeability and shear yield stress of magnetorheological fluid was revealed,which provides a useful reference for the transmission performance improvement of magnetorheological fluid transmission device.