Theory of Machines - GATE practice papers - Mechanical for Q. 359
Q. The punching rate of a punching press is 20 holes per minute. It is required to punch a hole of diameter 50 mm on a plate of 20 mm thickness. Press requires 10 N-m of energy per mm2 of sheared area. Calculate the energy required for punching work per second. (Marks: 02)- Published on 19 Oct 15a. 628318.2 Nm/s
b. 10471.97 Nm/s
c. 31416 Nm/s
d. none of the above
ANSWER: 10471.97 Nm/s
d =50 mm
t = 20 mm
Number of holes = 20 holes per minute
Energy required = 10 N-m/mm 2
Sheared area per hole = πdt
= π × 50 × 20
= 3141.6 mm2
Energy required to punch one hole = 3141.6 × 10
= 31416 N-m
and the energy required for punching work per second
= energy required per hole × number of holes per second
= 31416 × (20/60)
= 10471.97 Nm/s
