This study aims to investigate the effect of nonferromagnetic particle content on the properties of the magnetorheological fluid (MRF) under a dynamic magnetic field. A magnetic-induced viscosity calculation model under the temperature field was built. The influence on the viscosity of the MRF made in-house was analyzed by adding different proportions of nonferromagnetic particles, such as glass powder. Experiments show that a certain proportion of glass powder can increase the viscosity of the MRF. When the powder content is less than 10%, viscosity increases as the glass powder content increases. Conversely, viscosity decreases as the glass powder content increases when the content is more than 10% but less than 20%. These results indicate that adding micron glass powder to the MRF can increase the magnetic saturation limit of the MRF under the dynamic magnetic field and improve its settlement resistance by 25.6%.When 10% glass powder is added to the MRF containing 60% iron powder, sedimentation resistance increases by 25.6%. When the magnetic field intensity is 640 mT, the viscosity of the MRF increases by 6.6 times.

In this paper, semi-active control analysis and research on the vibration reduction system of vibratory roller with nonlinear stiffness and fractional damping are carried out. A two-degree-of-freedom semi-vehicle mathematical model with nonlinear stiffness and fractional damping is established, and the fractional calculus operator in the model is approximated by using the Oustaloup filter algorithm. The vibration characteristics of passive control, proportional integral derivative control, and fractional-order [Formula: see text] control on the vibration reduction system of the vibratory roller are simulated and analyzed. Results show that the vibration reduction effect of the first-stage vibration reduction device of the vibratory roller is evidently improved by using fractional-order [Formula: see text] controller. Compared with traditional passive control, the parameters are increased by about 40%, and the vibration intensity evaluation grade of the vibratory roller can be improved by about one level, which provides a new idea for the research of the vibration reduction system of the vibratory roller.

This study aimed to obtain super smooth surface medical implant laser power bed fusion Ti6Al4V samples. A self-modified magnetorheological polishing device and polishing fluid were used to polish the laser power bed fusion additive shaped Ti6Al4V samples to study the effect of the main factors such as abrasive grain size, polishing pressure, and polishing time on the surface roughness and material-removal efficiency of the samples. With continuously decreased Al2O3 abrasive-particle size, the surface roughness initially increased and then decreased, and the material-removal rate decreased. The polishing result of 5 µm Al2O3 was better, no new scratch damage was found after 3 µm Al2O3 polishing; With increased polishing pressure from 5 N to 25 N, the deeper the abrasive particles were pressed, the greater the cutting effect and the more obvious the scratches. Surface roughness initially decreased and then increased, and the material-removal rate increased from 1.19 nm/min to 8.68 nm/min. With continuously extended polishing time, the grinding and polishing effect continued to accumulate, and the surface quality significantly improved, decreasing from 366.33 nm to 19.77 nm. These results showed that magnetorheological polishing technology was very effective in removing LPBF forming defects; the surface roughness was reduced by 96.27% and the additive defects can be completely removed.