| Magnetorheological fluids are magnetic intelligent materials controlled by an external magnetic field.The magnetorheological transmission device designed according to the mechanical properties of magnetorheological fluid has the advantages of easy control and environmental protection.However,when the magnetic particles in magnetorheological fluid reach magnetic saturation,the shear yield stress of magnetorheological fluid will no longer increase,which greatly limits the application of magnetorheological transmission device.In this paper,based on the extrusion strengthening effect of magnetorheological fluids and using shape memory alloy as the power source of extrusion magnetorheological fluids,a transmission mode of magnetorheological fluids extruded by shape memory alloy is proposed,and its transmission mechanism is explored.It provides a theoretical basis for increasing the applicable range of magnetorheological transmission device and a new idea for the application of shape memory alloy and magnetorheological fluid in the transmission device.The main research work of this paper is as follows:(1)The composition,chaining mechanism and constitutive model of magnetorheological fluid were introduced.The influence of thickening coefficient in Herschel-Bulkley model on shear stress of magnetorheological fluid was analyzed.Based on the magnetic dipole model and the friction surface film effect,the shear yield stress model and the extrusion-enhanced shear yield stress model of magnetorheological fluids are established.(2)The superelasticity and shape memory effect of shape memory alloy are introduced.the output force model and displacement model of shape memory alloy spring with and without axial displacement are established according to the material characteristics of shape memory alloy and the design method of spiral cylindrical spring.(3)The transfer modes of cylinder,disk,cone and arc magnetorheological transmission devices are introduced,the relationship between the transfer torque of cylinder,disk and cone magnetorheological transmission is compared.At the same time,the equation of transfer torque of shape memory alloy spring drive is established.Based on the characteristics of shape memory alloy and magnetorheological transmission device,the theory of shape memory alloy extrusion magnetorheological fluid transmission is established,and the equation of transfer torque is obtained.(4)Based on the established theory of shape memory alloy extrusion magnetorheological fluid transmission,the key size of the transmission device was designed,and the material parameters and size parameters of the shape memory alloy spring used were determined;The magnetic circuit of the transmission device is designed and the finite element analysis is carried out.The influence of the working clearance of magnetorheological fluid on the transfer torque of magnetorheological fluid was investigated.The influence of a variable surface magnetorheological device on the transfer torque of the device before and after the clearance change is analyzed.(5)The output force characteristics of the shape memory alloy spring are analyzed experimentally.The theoretical and experimental values of cylindrical magnetorheological transmission mode are compared and analyzed. |
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