## 1 Introduction  
Magnetorheological fluid (MRF) is a solid-liquid two-phase material formed by micron-sized magnetic particles uniformly distributed in a base fluid by the action of additives. Under the action of the magnetic field, the magnetic particles in the MRF are arranged into chains in the magnetic field direction. The liquid fluidity becomes poor, and the MRF shows solid-like mechanical properties. When the magnetic field disappears, the magnetic particles quickly return to a disordered state, and the MRF returns to a viscous liquid. MRF can complete the reversible transformation from Newtonian fluid to Bingham fluid in milliseconds under the action of the magnetic field, and the properties of the material, such as damping and shear yield stress, change continuously with the change in the magnetic field. Based on these characteristics, MRF can be used in such engineering fields as transmission and vibration damping [1, 2]. Shape memory alloys (SMAs) are a class of smart materials with superelasticity and a shape memory effect whose internal metallurgical structure interchanges between low-temperature martensite and high-temperature austenite when the temperature changes. The shape memory effect of SMAs can be used for the purpose of adaptive control and stroke output [3]. The application of MRF and SMAs in transmission has received a lot of attention from a large number of researchers. [PERSON] et al. [4] derived the torque equation for MRF brakes, providing a theoretical basis for the design of MRF actuators. [PERSON] [5] proposed a multi-gap cylindrical magnetorheological (MR) brake to improve the braking torque by increasing the working area of the magnetorheological fluid. [PERSON] et al. [6] investigated a disc-type MR clutch with a composite cylinder, and increased the torque compared with the disc-type MR clutch by 1.45 times. [PERSON] et al. [7] designed an MR clutch with a helical fluid flow channel, which improved the durability of the clutch by 42%. [PERSON] et al. [8]designed a tapered-gap MR drive and enhanced the performance of the MRF by axial squeezing, which combined shear and frictional forces for torque transmission. To control the total volume of the MR transmission device while improving the transmission performance, [PERSON] et al. [9] proposed a cycloidal corrugated MR transmission device with composite shear and squeeze modes, which enhanced the anti-damage capability of the magnetic chain. The torque equation was established based on the Metal Plastic Deformation Theory, which greatly improved the torque transmission capacity of the device at the same volume. [PERSON] et al. [10] proposed an MR damper based on the helical flow mode, and the torque equation was derived based on the consideration of the fluid flow pressure. An experimental analysis was also conducted on the torque performance at different rotational speeds, and the experimental results showed that the new MR damper increased the torque density of the transmission while limiting the volume. SMAs are usually machined into spring shapes for transmission applications. [PERSON] et al. [11] established incremental constitutive equations between stress, strain, and temperature and proposed a method for finite element simulation of complex SMA structures. [PERSON] et al. [12] proposed an SMA actuator with the nonlinear dynamic properties of human muscles and established an analytical expression for the damping coefficient of the actuator. [PERSON] et al. [13] introduced a design concept for an SMA rotary actuator in order to transform the linear motion of SMA springs into high-torque rotary motion and explained its thermodynamic behavior based on experiments. The above-mentioned studies mainly focus on the application of MRF or SMAs alone, and less on the combined application of the two materials. Furthermore, since the shear stress of MRF decreases with increasing temperature, especially at high temperatures, its performance decreases significantly [14].