Tuning fork modal analyis using FEA

[lerlo]

Hi, when we strike the tuning fork, we hear the first mode right?

So how do we excite the structure to get the the subsequent modes?

[eamonnmcstravick]

Great Stuff Dave, I carried out an analysis with very similar results using NX I-DEAS....

[Aresholewins]

The fundamental mode should be tune A 440Hz

[DrDaveBilliards]

@Aresholewins

The tuning fork we used was C523.3 (an octave above middle C).

[rasmasyean]

@ 01:35 is the fork moving slightly back and forth along its long axis? Why doesn't your finger dampen that?

[DrDaveBilliards]

@rasmasyean

There is slight vibration along the long axis due to centrifugal force from the rotating tines. The fingers do damp this motion, but not very fast because the amplitude is so small.

[jashalen]

Excellent and informative video. Thank for doing this.

[DrDaveBilliards]

Thank you ... and you're welcome.

[Chillysum]

Hallo Dr. Dave:

It's amazing in your video! I'm a beginner and i wonder what FEA software exactly do you use? Which fundamental subjects do i need in order to simulate the vibration models of a tuning fork? Thanks a lot!

[DrDaveBilliards]

Pro-Mechanica was used. Whatever FEA program you are using should come with help screens and tutorials to help you get started.

[sk1nsane]

i am modelling an undamped free hanging plate . My problem is the first mode in abaqus shows that the plate is in first torsion but experiment shows that the plate is in first bending . Do i have to put any BC for a hanging plate ? . Any comment would be appreciated .

[DrDaveBilliards]

There should be no BCs for a hanging plate.

[ravinethi]

i have the field data (accelero meter outputs) of a a big motor casing.i have to validate my FEA modal analysis vth the feild data....how can i do that...after completing the analysis.like....post processing....

very very very thanks in advance

[DrDaveBilliards]

There are no simple answers to these questions, and I'm probably not the best person to try to answer them anyway. I recommend talking to an FEA software company ... ask to speak to an "applications engineer."

Good luck,

Dr. Dave

[AlderE87]

I am now trying to carry out a modal analysis on my structure, I was wondering how you went about setting up your model? - What step and loads/boundary conditions do you use? I know you said it was unconstrained but I am unsure how you do that?

Although the constrained model is probably more appropriate for what I want - do you just put in boundary conditions as usual for that?

[DrDaveBilliards]

I recommend you read your software help screens and/or manuals for modal analysis information. It seems like you need some more background first before you attempt an analysis.

[AlderE87]

I have used Abaqus for static stress and deformation analyses before but have never done any dynamic or vibration analysis. How would you go about finding the damping when the fork is constrained by the fingers?

Thanks

Liz

[DrDaveBilliards]

We just experimented with different numbers to get a reasonable response. The other thing difficult to quantify is the mass and stiffness properties of the finger skin-flesh-bone composite.

You could estimate a damping ratio by measuring ring-down time of a fork.

Regards,

Dr. Dave

[AlderE87]

Thanks.

I was also wondering how your model was setup, is the input force a frequency or impact and where is it applied.

I am trying to model the vibration transmission across a honeycomb panel (ie an input vibration at one end & measure the output at the other). At present I have no idea where to start as I have only used Abaqus for static stress and deformation problems.

Any ideas or information on setting up vibration models would be much appreciated.

Thanks again,

Liz

[DrDaveBilliards]

Modal analysis doesn't require a force or impact.

Dr. Dave

[GreatestPotential]

thanks for the demonstration!

[DrDaveBilliards]

You're welcome.

Dr. Dave