This study investigates the temperature distribution characteristics, temperature rise behavior, and the thermal effects on the output torque in a Permanent Magnet/Magnetorheological Fluid (PM/MRF) variable-stiffness drive joint through a combined approach of simulation and experimentation. First, a thermal simulation model of the joint was established using COMSOL Multiphysics, and steady-state and transient temperature field analyses were conducted under slip powers ranging from 25 W to 100 W. The steady-state results show that, when the joint reaches thermal equilibrium under 100 W, its internal maximum temperature is 113 °C, which falls within the allowable operating temperature range of the MRF. Transient simulations indicate that, within 180 s, the temperature in the working area of the joint continuously rises, but the rate of temperature increase gradually slows down, with a maximum temperature rise of 18.35 °C observed in the transmission mode. Furthermore, an experimental test system was constructed to conduct temperature rise characteristic tests and torque temperature characteristic tests on the joint. The experimental results show that the maximum actual temperature rise measured within 180 s in transmission mode was 17.36 °C, slightly lower than the simulated prediction. Within the temperature variation range of 10 °C to 50 °C, the maximum reductions in driving torque and braking torque were 14.1% and 14.9%, respectively. The study demonstrates that, under short-term operating conditions, the effect of the internal temperature rise on the output torque is predictable and can be mitigated through closed-loop current compensation. These findings provide theoretical and experimental foundations for the thermal safety design and high-precision control of PM/MRF variable-stiffness joints.

Flow resistance is a critical determinant of the efficiency and economics of a slurry pipeline. This study aims to reduce pipeline resistance by integrating a swirler to enhance particle suspension. The variation laws of slurry conveying resistance with and without a swirler under various conveying conditions were investigated. Whether a swirler is present or not, the conveying resistance increases with an increase in the conveying velocity (1~6 m/s), volume concentration (10~50%), particle diameter (0.1~5 mm), particle density (1100~1500 kg/m³), and pipe inclination (0~90°). It decreases with an increase in the pipe diameter (50~200 mm). A moderate swirling intensity reduces the resistance in high-velocity large-particle slurry transport. Considering the swirling flow characteristics in the conveying pipeline, resistance loss calculation models accounting for these characteristics were established for different flow states of the slurry in the pipeline. Taking into account the swirling characteristics in the conveying pipeline, a calculation model for resistance loss of the slurry in different flow states within the pipeline was established. The average error between this model and the experimental results was 9.04%.