FREQUENCY ANALYSIS OF A ROTATING SHAFT
AIM: TO RUN A FINITE ELEMENT FREQUENCY ANALYSIS FOR A ROTATING SHAFT USING SOLIDWORKS SIMULATION.
OBJECTIVE:
- To create 3D model of shaft.
- To perform Frequency analysis simulation study for the shaft.
- To obtain a plot for five different Amplitudes.
- To find the critical frequencies.
- To compare the results.
OVERVIEW:
In solid mechanics, in the field of rotodynamics, the critical speed is the theoretical angular velocity that excites the natural frequency of a rotating object, such as a shaft, propeller, leadscrew, or gear. As the speed of rotation approaches the object's natural frequency, the object begins to resonate, which dramatically increases system vibration. The resulting resonance occurs regardless of orientation. When the rotational speed is equal to the numerical value of the natural vibration, then that speed is referred to as critical speed.
The simplest way to describe resonance is the amplification of vibration. The vibration being amplified could originate from a number of sources: unbalance, misalignment, pump vane vibration – almost any source of vibration can cause resonance. And that vibration does not have to be a problem in itself. For example, resonance can cause slight unbalance to appear as if the rotor is seriously out of balance.
The vibration that arises in a well-balanced rotor, at a particular rotational speed, is caused by small differences in the rotor density and minor machining variations. This results in a miniscule movement of the center of mass away from the center of the axis of rotation. As speed increases, the elastic forces of the metal and the radial forces caused by rotation become unbalanced and vibration occurs. This vibration increases shaft deflection and can result in component wear (seals, wear rings and bearings) and even shaft breakage. If speed continues to increase, this natural frequency disappears and vibration will cease, but at an even higher speed, yet another natural frequency will be encountered. The lowest rotational speed at which this natural vibration occurs is called the first critical speed.
PROCEDURE:
Firstly, we will create 3D model of the shaft
Now we will create a new study with Frequency Analysis and Provide the material, as Alloy steel
Providing the Support, as –
Bearing support-1
Bearing support-2
Creating mesh
Then we will run the simulation and Define different mode shapes
Now we can get the required results by clicking on the result section.
RESULTS:
Amplitude-1
Amplitude-2
Amplitude-3
Amplitude-4
Amplitude-5
COMPARISON:
Data
Plot
CONCLUSION:
We have obtained the Resonant frequencies at different mode shapes (Amplitudes) and to avoid the failure, the shaft should not be rotated as for critical frequency.
Link for Plots, Results –
https://drive.google.com/file/d/1HwiI27HT2sgBXqk2MA4Han-VFKf356uB/view?usp=sharing