This article presents the design and multi-physics coupling analysis of a shear-valve-mode magnetorheological fluid damper with different piston configurations. The finite element model is built to study the effects of the shape of the piston slot and magnetism-insulators at both ends of the piston yoke on the performance of the magnetorheological damper. Particle swarm optimization and finite element simulation are combined to optimize the structural parameters of the magnetorheological damper. The influences of different piston configurations on the magnetic flux density in the working gap, the shear stress, the viscous stress, and the dynamic range are investigated. The simulation results reveal that the magnetorheological damper, in which the corners of the piston slot are chamfered and the edges of the magnetism-insulators are filleted, exhibits a better damping performance. Furthermore, magnetorheological dampers with and without magnetism-insulators are fabricated. The influences of control current, displacement, and velocity on the mechanical performance of the magnetorheological dampers are experimentally investigated, and the experiment results are in accordance with the theoretical derivation and finite element simulation results.

This paper proposes a scheme to control the low-frequency vibration of pipelines by using magneto-rheological (MR) vibration reduction technology. The state equation and the transfer function of the pipeline system are established, and its stability and the sinusoidal excitation response are analyzed. The prototype of MR damper is developed. The dynamic characteristics of MR damper are tested and the double-sigmoid model of MR damper is established. The two-state control, Proportion Integration Differentiation (PID) control and sliding-mode-variable-structure (SMVS) control methods of pipeline vibration using MR damper are analyzed comparatively, and the vibration control laws are deduced. The simulation analyses are carried out to predict the control effect of different pipeline vibration control algorithms. The verification tests through a semi-active measurement and control platform are carried out, and the feasibility and applicability of different pipeline vibration control strategies are analyzed. The test results show that the three kinds of pipeline vibration control methods based on MR damper can effectively control the pipeline vibration. Especially, SMVS control has the best vibration control effect, the pipeline amplitude drop and the acceleration drop can reach 22.31 dB and 16.34 dB respectively, while the amplitude attenuation rate and the acceleration attenuation rate can reach 92.34% and 84.77%, respectively.

Aiming at the problem of low-frequency vibration of the hydraulic pipeline, a new type of semi-active damping magnetorheological (MR) damping clamp structure is designed. The structure size and material of the MR damping clamp were determined. The control model of the vibration damping system was established, and the control method combining fuzzy control and Proportional-Integral-Derivative (PID) control was used to carry out the numerical simulation, which proved that the fuzzy–PID control algorithm is effective and stable. The results show that the MR damping clamp proposed in this paper can effectively suppress the axial displacement and acceleration of the hydraulic pipeline in the excitation frequency range of 1 Hz~10 Hz. This research provides a new technical approach for low-frequency vibration control of hydraulic pipelines.

To improve the abrasion resistance performance of the critical tribopairs within water hydraulic piston pumps, tribological characteristics of the stainless steel 17-4PH and 17-4PH coated with Cr₃C₂-NiCr, WC-10Co-4Cr, Cr₂O₃ and Al₂O₃-13%TiO₂ sliding against carbon fiber reinforced polyetheretherketone (CF-PEEK) composite under water-lubricated condition were experimentally studied using a pin-on-ring test bench with different working conditions. It has been demonstrated by the experimental results that the tribological behaviors of CF-PEEK/cermet coatings tribipairs were better than that of CF-PEEK/17-4PH tribopair under water lubrication. However, the Cr₃C₂-NiCr coating could be damaged under high rotational speed. Due to the reaction film produced by the Al₂O₃-13%TiO₂ and water, the CF-PEEK/Al₂O₃-13%TiO₂ material combination exhibits more excellent tribological behaviors than other tribopairs lubricated with water, and could preferentially be used in water hydraulic piston pumps.