Changhe Li

Feasibility investigations on compound process: a novel fabrication method for finishing with grinding wheel as restraint

This article describes the validity of a compound precision finishing process that combines grinding with abrasive jet finishing for micro-removal machining. Experiments were carried out with a M7120 plane grinder and a workpiece material of 40Cr steel, which was ground to a surface roughness with a mean value of Ra = 0.6 μm. The machined surface morphology was studied using a scanning electron microscope (SEM), and a metallography microscope. Microcosmic geometry parameters were measured with a TALYSURF5 instrument. The experimental results show that this novel processing method can effectively diminish longitudinal geometry parameter values of the ground surface, moreover attain an isotropic surface and uniform veins in the parallel and perpendicular machining directions. Furthermore, the finished surface has little comparability compared with a grinding machining surface. The effectiveness of the process was verified.

Theoretical Analysis and Experimental Evaluation Surface Morphology Integration of Grinding and Precision Finishing

The integration manufacturing technology is a kind of compound precision finishing process that combined grinding with abrasive jet finishing, in which inject slurry of abrasive and liquid solvent to grinding zone between grinding wheel and work surface under no radial feed condition when workpiece grinding were accomplished. The abrasive particles are driven and energized by the rotating grinding wheel and liquid hydrodynamic pressure and increased slurry speed between grinding wheel and work surface to achieve micro removal machining. In the paper, the machining process validity was verified by experimental investigation and theoretical analysis. Experiments were performed with plane grinder M7120 and workpiece material 40Cr steel which was ground with the surface roughness mean values of Ra=0.6 mum. The machined surface morphology was studied using scanning electron microscope (SEM) and metallography microscope and microcosmic geometry parameters were measured with TALYSURF5 instrument. The surface topographical characteristics were evaluated with correlation of random process about machined surface before and after finishing. The results show that longitudinal geometry parameter values of finishing machining surface were diminished comparing with ground surface, and the mean ripple distance was decreased and, ripple and peak density were increased. Furthermore, The finished surface has little comparability compared to grinding machining surface. The isotropy surface and uniformity veins at parallel and perpendicular machining direction were attained by abrasive jet precision finishing with grinding wheel as restraint.

Analysis and numerical investigation for thermal stress on arc spraying 3Cr13 coating

The theoretical analysis for arc spraying 3Cr13 coating thermal stress has been made; the heat conduction temperature field and stress field model for arc spraying 3Cr13 molten drop has been built and numerical simulation has been done for theoretical model. The result is proven that: when the high temperature molten drop is deposited on the matrix, the matrix temperature is sharply rising. However the molten drop coating has a shock chilling process that the molten drop temperature is suddenly dropping from 2,270 K to 400 K after melting to cover the matrix and finally the coating and matrix jointly drop to the room temperature 300K after 190s. The coating is exposed to tensile stress while the matrix is exposed to pressure stress. Furthermore, the lower the coating temperature and the less the matrix temperature, the smaller the radial stress that the coating and matrix are exposed to. The coating tensile stress is the minimum when the coating temperature is 1,000 K. The flying speed of particle along w...