Study on diamond cutting-to-burnishing for thermal-force dispersion in dry metal grinding

摘要

In metal grinding, abrasive grain cutting depends on grain edge sharpness for material shear deformation, but the thermal-force concentration on the grain-workpiece interface wears the sharp cutting edges and damages workpiece surface. In single-diamond grinding, a cutting-to-burnishing is proposed for the thermal-force dispersion by increasing the cutter flank surface and decreasing the relief angle to zero. The objective is to explore the dry grinding behavior from the grain cutting to burnishing. First, the grinding force and workpiece temperature were modeled with the mechanical friction between the diamond and metal in single-diamond grinding. Based on the flank area of the thermal-conductive diamond, a transition coefficient was introduced to characterize the cutting-to-burnishing. Finally, it was applied to the dry grinding experiment of hardened steel. It is shown that from the cutting to burnishing, the workpiece force dispersion is triggered along with diamond graphitization suppression, and the workpiece thermal dispersion is finally achieved. This indicates that increasing the transition coefficient from 0.05 % to 0.79 %, which is positively related to the cutting depth, decreases the normal contact pressure by 94 %, the local workpiece temperature rise by 73 % and the diamond temperature rate by 91 %, thus leading to the decrease of both workpiece damage and diamond edge wear. The cutting-to-burnishing with thermal-force dispersion achieves a polishing-alike smooth and microburr-free metal surface with 51-nm-Ra while a larger residual compressive stress and hardened layer thickness, compared to general polishing. Hence, dry grinding may improve the smoothened surface integrity by diamond cutting-to-burnishing at large cutting depths.

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