Frequency Analysis of a Rotating Shaft

AIM:

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

INTRODUCTION:

SolidWorks Simulation module is used to analyze the resonant frequencies of a rotating shaft.

THEORY:

A rotating shaft not only rotates but also wobbles around its axis. Due to wobbling, the shaft undergoes a transverse motion which creates vibration in the arrangement. This is due to large amplitude of vibration occuring at particular frequencies called natural frequency. If the shaft runs at a frequency equal to or close to its natural frequency, this frequency is called resonant frequency. So it is very important to find out the resonant frequencies of the rotating shaft at which the shaft, if it is operated, will lead to failure (i.e., breakage) of the shaft which is dangerous since it can cause a huge wreckage to the nearby machineries and people.

EXPLANATION:

A SolidWorks model of a rotating shaft is created.

The material applied for the model is Alloy Steel.

Once the model is created, the frequency analysis is carried out by giving necessary boundary conditions. Two bearing fixtures are set on either of the stepped circular part of the shaft.

Once the boundary condition is set, a mesh of 8mm size is created to get an accurate result against the default mesh size of around 13-14 mm recommended by the software.

Once meshing is done, the simulation is made to run and the results are obtained as follows:

The above table shows the resonant frequencies for 5 mode shapes.

The model results are as follows:

MODE SHAPE 1:

MODE SHAPE 2:

MODE SHAPE 3:

MODE SHAPE 4:

MODE SHAPE 5:

CONCLUSION:

From the results obtained, we can clearly see that there are 5 mode shapes corresponding to the resonant frequencies. Hence we can infer that the rotating shaft should not be operated in these frequency values so that the shaft runs smoothly and its life can also be kept as long as possible.