Frequency Analysis of a rotating shaft
Objective: To find out the critical frequencies of a rotating shaft in Solidworks
Problem Statement:
To create the model in Solidworks according to the dimensions that you see fit. Model it in Solidworks according to the image shown below
Conduct a frequency analysis and apply a bearing fixture on the stepped face of the rod at the two ends and perform the analysis.
Find out 5 mode shapes and list the resonant frequencies
Theory:
Vibration analysis of industrial machinery has been around for many decades, but gained prominence with the introduction and widespread use of the personal computer. Vibration Analysis refers to the process of measuring the vibration levels and frequencies of industrial machinery, and using that information to determine the “health” of the machine, and its components.
When an industrial machine (such as a fan or pump) is operated, it generates vibration. This vibration can be measured, using a device called an accelerometer. An accelerometer generates a voltage signal, proportional to the amount of vibration, as well as the frequency of vibration, or how many time per second or minutes the vibration takes place. This voltage signal from the accelerometer is fed into a data collector, which records this signal as either a time waveform (amplitude vs. time), as a Fast Fourier Transform (amplitude vs. frequency), or as both. This signal can then be analyzed by a trained vibration analyst, or by the use of a “smart” computer program algorithm. The analyzed data is then used to determine the “health” of the machine, and identify any impending problems in the machine, such as misalignment, unbalance, a bearing or lubrication problem, looseness, and more.
The use of vibration analysis can determine problems caused due to improper installation, machining errors, insufficient lubrication, improper shaft or sheave alignment, loose bolting, bent shafts, and much more. It can, in most cases, detect these problems long before the damage can be seen by maintenance, and long before it damages other machine components.
The use of vibration analysis, condition monitoring, or predictive maintenance has made great strides increasing the usable life of machinery.
Study Setup:
Open Solidworks Part and create the following sketch in the top plane.
Then use the revolved boss/base to create the profile as shown below.
Use the study setup and select the vibration study.
Then apply the material as shown below.
Use the bearing supports in the fixtures option and select the faces as shown.
Create a mesh with appropriate mesh refinement.
Then use the mesh and run option to get the results.
Results:
This is a plot of the frequency for Mode Shape 1.
This is a plot of the frequency for Mode Shape 2.
This is a plot of the frequency for Mode Shape 3.
This is a plot of the frequency for Mode Shape 4.
This is a plot of the frequency for Mode Shape 5.
These are the list of frequencies for each mode as shown in the figure above.
Conclusion:
The transfer of energy can be visualized as occurring at certain discrete rates depending on the stiffness and mass of the system. These rates of vibration are called natural frequencies. Asociated with each of these rates of vibration is a shape of the structure called the mode shape. Every system's vibration behavior can be characterized by computing these natural frequencies and mode shape associated with them. The total vibration of the system can be formed by summing up different amounts of vibration in each mode. The amount of vibration in each mode depend on the type of excitation.
The excitation at or close to the natural frequencies must be avoided as this leads to very large responses/rather etc.
The simulation has been successfully run and the necessary results are plotted for each case.
References:
https://vibralign.com/resources/concepts/vibration-analysis/
Project Link: https://skill-lync.com/projects/frequency-analysis-of-a-rotating-shaft-169