In this paper, a double-side grinding method with variable position rotation is proposed, which changes the motion mode of the workpiece in the fixed distance rotation grinding from the grinding principle, and realizes the irregular planar motion of the workpiece in the isolation dics at the same time as the rotation. That is, the movement trajectory of the workpiece rotation center relative to the grinding tool is the curve of the change. Different grinding principles fundamentally overcome some defects of traditional planar grinding methods. A prototype model of variable position rotation grinding is established, and the feasibility of the new method is verified by simulation experiments. The simulation data also further proves the time-varying nature of this grinding method in improving the grinding trajectory, the uniformity of relative velocity distribution of grinding and the superiority and diversity of the mechanical wear of the grinding mechanism and the ability to adjust the grinding trajectory.

Micro-arc oxidation coatings were prepared on magnesium alloy AZ91D substrates at the different applied voltages in aluminate solution. The morphologies, phase components, and corrosion resistances of the coatings were investigated. The effect of the applied voltages on the microstructure and corrosion resistance of the coatings was also discussed. The results indicate that the coatings are uniform in thickness, and mainly composed of MgAl2O4 and MgO. There were many residual discharging channels on the coatings surface. The coatings improved the corrosion resistances of magnesium alloy AZ91D considerably. With the increase of the applied voltage, the thickness and the MgAl2O4 content of the coatings increase, while no significant variation is observed in the MgO content. The coatings surface becomes lower porosity and larger pore size with increasing of the applied voltage. In addition, the corrosion resistances of the coatings on magnesium alloy AZ91D surface are obviously superior to the magnesium alloy AZ91D substrate in the 3.5 wt. % NaCl solutions, and the effect is more remarkable at higher voltage.