| Popis: |
A three-dimensional cut-away tool for turning operations has been proposed to improve machinability of difficult-to-cut materials. The tool-chip contact geometry is determined such that the restricted length is proportional to the real uncut chip thickness in the direction of chip flow. The three-dimensional elastic-plastic and thermal finite element method has been employed to simulate the cutting mechanism of an 18%Mn-18%Cr high manganese steel (HB=241) with a sintered carbide cut-away tool. The simulation has revealed that there exists an optimum restricted length of around 1.2 times the feed, where the cutting forces become minimum, leading to the reductions of cutting temperature and tool wear. Measurements of the cutting forces, cutting temperature and tool wear have been conducted to validate the analytical predictions: the cut-away tool with optimum contact geometry brings a more than 10% reduction of tool wear in dry turning of the steel with a cutting speed of 60 m/min, a feed of 0.2 mm/rev, and a depth of cut of 2 mm. |
