8. This problem is aimed at comparing the effects of possibly changing one of the cutting conditions, namely cutting speed and the cutting tool material. Throughout, assume that except for cutting speed, all other cutting conditions are kept constant and that the machining time is inversely proportional to the cutting speed as described by Taylor's tool life equation. Coefficients of tool life equations for this problem are given in Table 4.4. (a) Assume that the current cutting edge material is K10 carbide and the work- piece material is GFRP. Furthermore, assume that the current speed is 20 m/min. Estimate the tool life T for this tool material at this cutting speed. (b) As a change in operating strategy, cutting speed will be selected to give a tool life of 3.5 h, so that cutting edges are changed about twice per shift. Find the cutting speed that will give this tool life for K10 carbide, and compute the ratio of this new machining time to the machining time in part (a). (c) Retain the operating strategy from part (b), i.e., the cutting speed is selected so that the tool life is 3.5 h. This time, PCD tool will be used as a tool material. With this new tool material, for T = 3.5h, compute the cutting speed and the ratio of this new machining time to the machining time in part (a). Table 4.4 Taylor's tool life equation coefficients for several tool-workpiece combinations. T in minutes, feed = 0.1 mm/rev, VB = 0.2 mm [22] Workpiece Tool d (mm) n UD-GFRP (V = 0.7) UD-GFRP (V= 0.7) CFRP filament wound CFRP filament wound GFRP (V = 0.5) GFRP (V = 0.5) aVB = 0.1 mm bDiamond-coated K10 K10 PCD K10 PCDa K10b K10 2.0 2.0 2.0 2.0 1.0 1.0 C 0.2334 90 0.1684 398 0.7813 1,640 0.4237 2,900 0.4069 565.6 0.2710 152.66 Cutting speed (m/min) 30-50 200-250 80-300 500-1500 100-300 100-300