Xiangfan Wu

To address the issue of unstable output torque in magnetorheological (MR) clutch due to temperature rise, this paper proposes a water-cooled MR clutch with helical channels. Through magnetic circuit modeling and simulation, the distribution characteristics of the magnetic induction intensity within the working gap and its key influencing factors were systematically analyzed. Results show that when the excitation current reaches 3.0 A, the magnetic induction intensity in the working gap reaches ∼560 mT on the right side and 400 mT on the left side, with the magnetic field aligned perpendicular to the shear direction of the MR fluid to effectively utilize its rheological properties. The width of the cooling water gap has a significant impact on the magnetic circuit performance. Experimental results show that at 3.0 A, the output torque reaches 72.5 N m, with a deviation from the theoretical value of 9.375%. During a 300 s operation, the helical channel water cooling system maintains the working temperature stably below 80 °C, reducing the temperature rise by more than 30% compared to the uncooled condition, significantly delaying the thermal performance degradation of the MR clutch. This work provides a practical design with validated magnetic and thermal performance for high-duty MR clutch applications.

The traditional vertical-shaft-impact sand-making machine has the problems of uneven discharge particles and discharge port wear. To solve these problems, the influence of the main structural parameters (number of impact rotors, angle of impact plates, angle of anvil, and number of teeth on the anvil) on sand production is researched through orthogonal testing and polar analysis. The results show that the parameters’ degrees of influence on the sand production rate are as follows: the angle of impact plates, the number of impact plates, the angle of the anvil, and the number of teeth on the anvil. The double rotor exhibits the best crushing effect when the number of impact rotors is six, the angle of the impact plate is 0°, the angle of the anvil plate is 0°, and the number of teeth on the anvil plate is 89. By taking the working speed of the double rotors as a factor, an equal-level uniform design table is constructed for the double-rotor crushing system. Polynomial regression analysis shows that the best crushing effect occurs when the accelerating rotor speed is 1200 r/min and the impact rotor speed is 585 r/min. Finally, the crushing characteristics of the double-rotor vertical-shaft-impact sand-making machine are simulated and analyzed to obtain the kinetic energy distribution of particles in the crushing chamber. The kinetic energy of particles in the main crushing area is determined, and the wear pattern of the discharge port and parts is identified.

Aiming at the drawback of unstable torque output caused by heat generation due to slip in magnetorheological fluid transmission devices, this paper proposes a new type of non-coaxial conical disk magnetorheological fluid transmission structure and deduces its mathematical model of output torque. The magnetic circuit design was carried out based on the conical disk configuration. The electromagnetic field analysis of the transmission device was conducted by the finite element method, and the influence laws of parameters such as the coil current, magnetic conductive material, the conical angle of the disk, and the working gap on the distribution of the magnetic induction intensity in the working area were obtained. The test system for the non-coaxial conical disk type magnetorheological fluid transmission device was established, and experiments on electromagnetic fields, transmission performance, torque response, etc., were carried out. Research results show that the magnetic induction intensity in the working area increases with the increase of the current in the excitation coil, decreases with the increase of the working gap between the two conical disks, and is positively correlated with the magnetic permeability of the conical disk and the magnetic conducting ring materials. The effective working area range and magnetic induction intensity of the governor both decrease as the conical angle of the disk increases. The magnitude of the magnetic induction intensity on the center line is basically the same, but the effective working area range corresponding to different angles shows significant differences.

Magnetorheological fluid exhibits shear-thinning behavior when subjected to high temperature environments exceeding 100 °C, which will significantly compromise the operational stability and reliability of the associated mechanical systems. To enhance the performance of magnetorheological fluid, this study selects soft magnetic particles, base carrier fluid, and surfactants based on their resistance to high temperatures and shear-thinning effects. A novel magnetorheological fluid with enhanced thermal stability and shear stability is subsequently developed by carefully selecting flake-shaped carbonyl iron powder, dimethyl silicone oil, and surfactant exhibiting both sedimentation stability and high temperature resistance. The apparent rheological properties and mechanical performance of the fluid are systematically evaluated. Experimental results indicate that the sedimentation rate of the prepared magnetorheological fluid is 3.86% after standing for 10 days, the thermal expansion rate at 200 °C is 12.8%, and the evaporation rate following repeated high temperature applications is only 0.66%. The shear yield stress of the prepared magnetorheological fluid is 31.2 kPa under the magnetic field of 817 mT. The prepared magnetorheological fluid demonstrates excellent thermal stability and shear-thinning resistance, which holds significant potential for enhancing the performance of magnetorheological devices in future applications.

Traditional belt deflection detection devices for underground belt conveyors in coal mines have problems, such as their single function, poor fault location and analysis accuracy, low automation level, and low reliability. In order to solve the defects of traditional detection devices, the belt deviation faults of the underground belt conveyor transport process require to be detected effectively and reliably. This paper proposes a belt deviation detection method based on machine vision. This method makes use of a global adaptive high dynamic range imaging method to complete the brightness enhancement processing of the underground image. Then the straight-line features of the conveyor belt edges are extracted using Canny edge detection and the Hough transform algorithm. In addition, a dual-baseline localization judgment method is proposed to realize the identification of band bias faults. Finally, a test bench for belt conveyor deviation was built. Testing experiments for different deviations were conducted. The accuracy of the tape deviation detection reached 99.45%. The method proposed in this study improves the reliability of belt deviation fault detection of underground belt conveyors in coal mines and has wide application prospects in the field of coal mining.

A magnetorheological fluid (MR fluid) is mainly composed of soft magnetic particles, surfactants, and the base carrier fluid. Among these, soft magnetic particles and the base carrier fluid influence the MR fluid significantly in a high-temperature environment. Therefore, a study was carried out to investigate the changes in the properties of soft magnetic particles and base carrier fluids in high-temperature environments. On this basis, a novel magnetorheological fluid with high-temperature resistance was prepared, and the novel magnetorheological fluid had excellent sedimentation stability, of which the sedimentation rate was only 4.42% after heat treatment at 150 °C followed by one-week placement. At 30 °C, the shear yield stress of the novel fluid was 9.47 kPa under the magnetic field of 817 mT: higher than the general magnetorheological fluid with the same mass fraction. Moreover, its shear yield stress was less affected by the high-temperature environment, reducing by only 4.03% from 10 °C to 70 °C. The novel MR fluid can be applied to a high-temperature environment, effectively expanding the application range of MR fluid.

Aiming to solve the problem of high-power magnetorheological fluid transmission heat dissipation, a new type of magnetorheological fluid drive disk is designed. The characteristics of the flow field and temperature field of high power MR fluid transmission devices are analyzed. Meanwhile, the influence of factors, such as rotating speed, inlet velocity, inlet position, diameter and number of magnetic columns, on the flow field are also investigated. Furthermore, the distribution characteristics of the ultimate slip power and the transient temperature field are obtained. The experimental platform of an MR fluid transmission device was established, and the torque transfer performance and heat dissipation performance were tested. The experimental results show that the device has good heat dissipation performance and can transfer high-power torque.