HW3 - 21.45 t=0.1 mm width of cut = 5mm t c =0.2 mm V c = 2...

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ME363 HW3 Due: 9/28/2011 1. Calculate the expected main cutting force in an orthogonal machining operation where the shear stress is 35,000 psi (241 MPa). The rake angle is +10 o , the feed is 0.015 inch (0.381 mm) and the depth of cut is 0.100 inch (25.4 mm). Assume that the F n /F s ratio is equal to 1 where F n = force normal to the shear plane and F s = shear plane force). The chip thickness ratio is 0.6. 2. It is desired to determine the efficiency of a lathe. A cutting test was performed with velocity of 165 ft/min (50 m/min), feed of 0.010 inch (0.254 mm), and depth of cut of 0.100 inch (2.54 mm). During the test, the dynamometer reading indicated 450 lbs (2000N) in the cutting direction and 200 lbs (890 N) in the feed direction. The wattmeter reading for the main spindle motor was 2.68 HP (2 KW). (a) Determine the efficiency of this machine. (b) What is the specific horsepower of this material? 3. An orthogonal cutting operation has been performed with the following conditions (textbook
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Unformatted text preview: 21.45): t=0.1 mm, width of cut = 5mm, t c =0.2 mm, V c = 2 m/s, rake angle=10 , main cutting force= 500N, thrust cutting force= 200N. Calculate the total percentage of the total energy dissipated in the shear zone. 4. Calculate the shear plane temperature rise during orthogonal machining of mild steel using the following data gathered. Assume that the percentage of heat going to the work =0.1. Cutting data cutting force = 890 N (200 lbf), thrust force = 667 N (150 lbf), cutting speed V= 2 m/s (394 fpm), undeformed chip thickness=0.25 mm (0.0098 in.), width of cut=2.5mm (0.098 in.), cutting ratio = 0.3, rake angle=0 material data for mild steel density= 7200 kg/m 3 (0.26 lb/in 3 ), heat conductivity k= 43.6 W/m-K (320.6 Btu-in/hr-ft 2- F), specific heat c= 502 J/Kg-K (0.12 Btu/lb-F)...
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