Frequency Analysis of a rotating shaft
OBJECTIVE:
To create a rotating shaft model in Solidworks, perform a frequency analysis and find the critical frequencies of the model.
SOLUTION:
Frequency Analysis is the study of the vibrations in a body, so as to design the model to avoid failures. Every part/body has a natural frequency with which it vibrates, when there is no repeated or continuous load acting on it. Care should be taken so to avoid applying loads on these bodies which makes it vibrate at its natural frequencies. The failure to do so, will result in a phenomenon called resonance, which will create large deformations which will be destructive for the body. Hence it is of prime importance to study perform a frequency analysis before the part is used in a mechanical system.
Modal analysis is the process of determining the inherent dynamic characteristics of a system in forms of natural frequencies, damping factors and mode shapes, and using them to formulate a mathematical model for its dynamic behaviour. The mode of vibration or mode is the property of a structure, which depends on the material properties and boundary conditions applied on the structure, and changes if any of these parameters changes. It’s defined by the resonant frequency, mode shape and modal damping.
The aim of this project is to perform a frequency analysis on a rotating shaft and to find the mode shapes and resonant frequencies.
The geometry of the rotating shaft is given below:
After creating the model, Alloy steel was assigned as the material for the part. The material properties are as given below:
The next step is to define the boundary conditions of the model. Both ends of the shaft was fixed using a bearing fixture. It was applied on the stepped face of the shaft as shown in figure.
The model was meshed using an element size 2.5mm.
RESULTS:
The modes shapes and the resonant frequencies of the system were obtained.
|
Mode No |
Frequency (rad/sec) |
Frequency (Hertz) |
Period (seconds) |
|
1 |
0 |
0 |
1e+32 |
|
2 |
3695.2 |
588.11 |
0.0017004 |
|
3 |
3695.4 |
588.15 |
0.0017003 |
|
4 |
12787 |
2035.1 |
0.00049137 |
|
5 |
12789 |
2035.4 |
0.00049131 |