Baik Jin Kim Are you talking about gyroscopic mode shapes or stationary mode shapes?

If stationary mode shape means nothing rotates when measuring 1st & 2nd bending natural frequencies in free-free mode, that is what I am looking for

You can use Polytec Laser Vibrometers. I can pass you the contact of the person who works with us from Polytec.

https://www.polytec.com/us/vibrometry/products

I was able to accurately measure mode shapes and resonance frequencies for structures in my research.

Thanks, Zaryab Shahid! I will look through this. Hope you are doing well.

Sorry for a late answer, Baik Jin Kim.

Although Polytec LDVs are a great tool, they are a bit expensive. I do not know the exact dimensions of your rig but I would start with standard testing methods such as impact testing using a modal hammer (as this is a quick and cheap method). The response can be measured using standard eddy current sensors or piezo accelerometers. High-quality hammers and accelerometers are produced by Endevco, Kistler, Brüel and Kjaer and others.

As for software, the best available software is probably ME'Scope from Vibrant Technologies. ME'Scope can work with binary files produced by wide-spread acquisition systems (DAQs) such as National Instruments, Brüel & Kjaer, Dewetron, Oros, Simulink / Matlab, Siemens etc. If you are looking for a low price, a National Instrument DAQ is a good starting point.

If you own a National Instrument DAQ, you can even use ME'Scope for a direct data acquisition (without data export/import).

There are also some software packages available under a GNU license, check e.g. OpenModal at http://www.openmodal.com/

https://github.com/ladisk/pyEMA might be useful.

ARTeMIS software with using accelerometers 2D or 3D are satisfied software and instruments to extract modal properties of a structure experimentally.

Here is a free one that is matlab based. The python one recommended by Nils works fine too, but there is no gui.

https://bwk.kuleuven.be/bwm/macec

if you search RG, you will find this question answered with more suggestions.

if you want also measurement and use NI hardware, ModalView is a low cost option worth a look. It can do most things, also ods at varying rpm, but does not separate few and be rotating modes. (The developer sometimes add things when asked nicely).

http://absignal.com/literature/index.php

/claes