3.19 Techniques for Analysing Earthquake Response
121
Prob. 3.8
Prob. 3.9
3.9 A 15 kg rotor has an unbalance of 3 × 10
− 3 kgm. Neglecting the mass of the
shaft, find the amplitude of vibration and force at each bearing for a 20 mm
diameter shaft.
3.10 Assuming a shaft to be simply supported between bearings, determine the
lowest critical speed if a solid disc of mass 5 kg is keyed to the centre of the
shaft. The diameter of the shaft 3 mm and the distances between bearings
200 mm.
3.11 An aircraft radio weighing 110 N is to be isolated from engine vibrations in
the frequency range between 20 and 40 Hz. What static deflection must the
isolators have for 85% isolation?
3.12 Turbines run through dangerous speed at resonance each time they started
or stopped when they are made to operate at critical speed. Assuming the
critical speed ω n to be reached with amplitude p 0 , determine the equation for
the amplitude building with time for an undamped system.
3.13 A water rotating eccentric weight exciter is used to produce forced vibration
of a spring supported mass, as shown in the Fig. When the speed of rotation
is varied, a resonant amplitude of 0.50 cm is recorded. When the speed of
rotation is increased considerably beyond the resonant frequency, the amplitude tended to be constant at 0.75 cm. Determine the damping factor of the
system.
121
Prob. 3.8
Prob. 3.9
3.9 A 15 kg rotor has an unbalance of 3 × 10
− 3 kgm. Neglecting the mass of the
shaft, find the amplitude of vibration and force at each bearing for a 20 mm
diameter shaft.
3.10 Assuming a shaft to be simply supported between bearings, determine the
lowest critical speed if a solid disc of mass 5 kg is keyed to the centre of the
shaft. The diameter of the shaft 3 mm and the distances between bearings
200 mm.
3.11 An aircraft radio weighing 110 N is to be isolated from engine vibrations in
the frequency range between 20 and 40 Hz. What static deflection must the
isolators have for 85% isolation?
3.12 Turbines run through dangerous speed at resonance each time they started
or stopped when they are made to operate at critical speed. Assuming the
critical speed ω n to be reached with amplitude p 0 , determine the equation for
the amplitude building with time for an undamped system.
3.13 A water rotating eccentric weight exciter is used to produce forced vibration
of a spring supported mass, as shown in the Fig. When the speed of rotation
is varied, a resonant amplitude of 0.50 cm is recorded. When the speed of
rotation is increased considerably beyond the resonant frequency, the amplitude tended to be constant at 0.75 cm. Determine the damping factor of the
system.