+1 vote
in Machine Dynamics by (34.3k points)
Calculate the work done per minute by a punch tool making 20 working strokes per min when a 30 mm diametre hole is punched in 5 mm thick plate with ultimate shear strength og 450 Mpa in each stroke.

(a) 10.69 kNm

(b) 20.69 kNm

(c) 30.69 kNm

(d) 40.69 kNm

The question was posed to me in an online interview.

My question is based upon Effect of Gyroscopic Couple on a Naval Ship during Steering and Pitching topic in portion Gyroscopic Couple and Precessional Motion of Machine Dynamics

1 Answer

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by (38.6k points)
The correct answer is (a) 10.69 kNm

The best explanation: Force required to punch one hole = area shared x ultimate shear strength = пdt x Ss

Ss = п x 30 x 5 x 450/1000 = 212.05 kN

Work done/min = Average force x Thickness of plate x No. of holes/min

              = 212.05/2 x 5/1000 x 20 = 10.69 kNm.

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