Frequency Analysis of a rotating shaft

INTRODUCTION:

• Natural Frequency: All physical structures have natural frequencies.These are the frequencies at which the structure will tend to vibrate when subjected to certain external forces. These frequencies are dependent on the way mass and stiffness are distributed within the structure.

• Resonance: Resonance is a phenomenon in which a dynamic force drives a structure to vibrate at its natural frequency. When a structure is in resonance, a small force can produce a large vibration response.

What does this mean in practice? When a dynamic force is applied to a physical object, it will vibrate. When a force is applied at the object’s natural frequency, it goes into resonance, and a higher amplitude vibration response is created. Resonance can cause discomfort or be catastrophic.

OBJECTIVE:

This project aims to find out the natural frequency of a rotating shaft. So that the operating conditions of the system can be taken care without causing resonance. The first five mode shapes and natural frequencies are found out.

BOUNDARY CONDITIONS:

The rotating shaft is considered as Homogeneous, isotropic bodies

1. Shaft materiall is taken as Alloy steel.
2. Applied a bearing fixture on the stepped face of the rod at the two ends.
3. Mesh conditions.

Mesh type : Solid mesh

Mesher used : standard mesh

RESULTS:

MODE SHAPE 1:

MODE SHAPE 2:

MODE SHAPE 3:

MODE SHAPE 4:

MODE SHAPE 5:

Frequency Number	Rad/sec	Hertz	Seconds
1	0.65659	0.1045	9.5693
2	8004.8	1274	0.00078492
3	8019.9	1276.4	0.00078345
4	22613	3599	0.00027786
5	22620	3600.1	0.00027777

CONCLUSION:

The first five mode shapes and natural frequencies are found out. Hence that the operating conditions of the system can be taken care accordingly without causing resonance.