Frequency Analysis of a Rotating shaft - FEA

FREQUENCY ANALYSIS OF A ROTATING SHAFT

Aim :

To conduct a frequency analysis on a rotating shaft and to find out the 5 mode shapes and list the resonant frequencies corresponding to the mode shapes.

Introduction :

Resonant vibration in mechanical structures such as pumps, turbines and motors occurs when a natural frequency is at or close to a forcing frequency such as rotor speed. When present, this condition can cause severe vibration levels by amplifying small vibratory forces from machine operation.

Description :

The sketch of the rotating shaft was done first with the below mentioned dimensions and the revolved base option was used to make an extrusion for the sketch along the longest dimension as the axis. The dimensions of the sketch are as follows :

All measurements are in millimeters (mm)

The extruded part of the sketch is as follows :

Conditions, Models & Mesh :

Material applied : Alloy Steel

Fixed Geometry : Stepped cicular face of the rod at the two ends

Mesh : Default mesh

Number of mode shapes : 5

Model and Mesh :

Observations :

Mode Shape 1 :

Mode Shape 2 :

Mode Shape 3 :

Mode Shape 4 :

Mode Shape 5 :

Resonant Frequency :

The resonant frequencies for the 5 mode shapes are as follows :

Conclusion :

From the above obtained results for 5 mode shapes and their respective resonant frequencies, it can be clearly inferred that the rotating shaft cannot be rotated at these frequencies as they damage and degrade the shaft for a higher value and necessary changes must be made to make the shaft reliable, durable and to operate smoothly for a longer run.