How can I get the second and third natural frequency of a cantilever beam experimentally??
The problem that I am facing is that I got only the first natural frequency.. I can't get other frequencies..
Have you tried a sweep sine test? While increasing the frequency, you would hit the first, then the second, then the third resonance.
You may visit the VLAB portal of education wherein Free Vibration of a Cantilever Beam (Continuous System) experiment procedure is given with complete information. The link is provided for your convenience .
https://vlab.amrita.edu/?sub=3&brch=175&sim=1080&cnt=1
@Vyacheslav Ryaboy, is there any equipment needed for this test? And how can I hit the beam 3 times.. Please explain
Dear Murana Awad,
Please check these links.
https://studylib.net/doc/6941045/mec316-l4---natural-vibration-modes
https://vlab.amrita.edu/?sub=3&brch=175&sim=1080&cnt=1
Article Modeling and Analysis of Multiple Attached Masses Tuning a P...
Best regards
To expand on the answer provided by Vyacheslav Ryaboy, when performing the increasing-frequency sine sweep test, you would pass through the first resonance frequency of the cantilever beam. This is what is referred to as "hitting" the first resonance frequency. If you continue to increase the frequency, you will eventually reach and pass through the second resonance frequency. If you continue to increase the frequency further, you will eventually reach and pass through the third resonance frequency.
Depending on the equipment at your disposal, you may wish to use an impact hammer to simultaneously excite a number of modes of vibration. The measurement system would likely have the ability to compute the transfer function between the response and the excitation force. The frequency response curve would generally show the first few natural frequencies of vibration of the cantilever beam, dependent somewhat on the bandwidth of the force impulse and also the point of application of the transient excitation force.
The links provided by Om Prakash Chhangani and Mohamed-Mourad Lafifi give the formulas for the first three natural frequencies of a cantilever beam, as well as a graphical representation of the associated mode shapes. There are some suggestions for how to go about experimental testing there too.
What test equipment do you have available to conduct the experiments with?