Frequency Analysis of a rotating shaft

Objective:
To create a solid model of a rotating flywheel on a shaft and identify 5 critical frequencies by generating 5 mode shapes using Solidworks Simulation’s Frequency analysis feature.

Figure 1: Dimensions of the solid model created

Tools used:

Solidworks Simulation module

Pre-requisites:

A flywheel on a shaft modeled in Solidworks using the Solid modeling tools.

Boundary conditions:

Part type = Shaft with mounted flywheel

Material = Alloy Steel (See figure 4 for Material properties)

Fixtures = 2X bearing supports on either side of the shaft

Tensile load = 120 rad/s Centrifugal force (Assumption)

Mesh size = 6 mm

No. of frequencies = 5

Incompatible bonding options = Automatic

Solver selection = Automatic (FFEPlus / Direct Sparse solver)

Figure 2: Material properties of Alloy Steel

Figure 3: Solid model of the flywheel on the shaft with bearing fixtures and direction of the cetrifugal force

Results:

After applying the aforementioned boundary conditions and settings, the following modes were identified by the simulation.

Mode 1:

Figure 4: Screen snippet of deformation at a frequency of 19.078 Hz.

Mode 2:

Figure 5: Screen snippet of deformation at a frequency of 335.78 Hz.

Mode 3:

Figure 6: Screen snippet of deformation at a frequency of 335.82 Hz.

Mode 4:

Figure 7: Screen snippet of deformation at a frequency of 1031 Hz.

Mode 5:

Figure 8: Screen snippet of deformation at a frequency of 1031.4 Hz.

The following are the resonant frequencies identified by the simulation for the 5 modes.
Mode Frequency (Rad/Sec) Frequecy(Hertz) Period(seconds)

1 119.87 19.078 0.05241600

2 2109.8 335.78 0.00297820

3 2110.0 335.82 0.00297780

4 6478 1031.0 0.00096993

5 6480.3 1031.4 0.00096959

Inference:
The 5 frequencies are identified as resonant frequencies. This tells us that when a system is designed with the above part, it should avoid operation in these frequencies since failure to do so can lead to devastating failures due to resonance.