+1 vote
in Machine Dynamics by (34.3k points)
Assuming the shaft to be freely supported. Calculate the whirling speed of the shaft : 2 cm diameter and 60 cm long carrying a mass of 1 kg at its mid-point. The density of the shaft material is 40 Mg/m^3, and Young’s modulus is 200 GN/m^2.

(a) 2598

(b) 2434

(c) 2756

(d) 2634

The question was asked in my homework.

I would like to ask this question from Critical or Whirling Speed of a Shaft in chapter Longitudinal and Transverse Vibrations of Machine Dynamics

1 Answer

0 votes
by (38.6k points)
Right choice is (a) 2598

The best I can explain: I = πd^4/64 = 7.855×10^-9 m^4

d due to 1 kg mass = 28×10^-6 m

d due to mass of the shaft = 0.133×10^-3m

substituting these values into the frequency relation of transverse vibrations

we get

f = 43.3 Hz

Therefore Nc = 43.3×60 = 2598 rpm.

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