FRF with different rubber thickness

[wshrr]

hi all,

The question is about my sandwich beam "two steel and a viscoelastic material with 50ib mass at the tip".

When I made many run with different rubber thickness, I saw two different cases



1-The H"rubber"=<H"steel"



2-The H"rubber"=>H"steel"



Why the decrease in rubber thickness in Case 1 is increases the damping and in Case 2 decreases the damping. The decrease in rubber thickness should always give me increase in damping.
Any help is appreciate it.

[Jorgen]

Are you talking about experimental data or finite element simulations?

If you are using FE simulations. What material models did you use to represent the response of the steel and the rubber?

-Jorgen

[wshrr]

thank you Dr.Jorgen

i'm using ABAQUS simulations and i'm using hyperelastic "Mooney Rivlin" +viscoelastic prony series" model for my viscoelastic material.what about the steel?i'm only using "E & density" for steel.

for element type,i'm using C8D20 for steel, and C8D20H for my viscoelastic?

Do you think there is something wrong in these material models or element types.

thank you so much for your help.

[Jorgen]

Your simulation sounds good. My only concern is the Mooney-Rivlin + Linear viscoelasticity model. That model will only be less accurate at "large" strain. Perhaps that is causing the results that you did not expect...

- Jorgen

[wshrr]

what do suggest Dr.Jorgen for this problem.I'm only looking for the result between 1-40 HZ.Is changing the Mooney-Rivlin will solve the problem.What is the best model for my case.Thank you again.

[Jorgen]

Accuracy concern is more dependent on the strain amplitude than the frequency. What strain amplitudes are you interested in?

- Jorgen