An industrial machine of 750 kg is fixed securely to the upper floor of a shoppi
ID: 1719307 • Letter: A
Question
An industrial machine of 750 kg is fixed securely to the upper floor of a shopping center building having two floors. Unfortunately, at the start of the machine we see that the floor of the building vibrates in an acceptable way. So we appealed to your services to correct the situation with a dynamic absorber suspended directly below the machine floor.
By varying the speed of the machine, it was observed that the maximum amplitude of vibration occurs at 1680 r/min. Preliminary tests with a dynamic absorber of 375 kg tuned at the operating speed of 1750 r/min, yields new resonance frequencies of 1460 and 2015 r/min.
If the design criteria require that the resonance frequencies of the modified system fall outside the frequency band between 1350 and 2100 r/min, determine:
a) the equivalent mass of the floor;
b) the characteristics (k2 and m2) of the dynamic absorber required
Explanation / Answer
Equivalent mass = 750 + 375 = 1125 kg