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Frequency dependent Isolation analysis of viscoelastic material in abaqus  


joe hormon
Posts: 9
(@joe hormon)
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Joined: 6 years ago

Hello Sir,

I am doing shape optimization study of a damper, used for isolation application and its material is viscoelastic material.

For this analysis, i am using Abaqus software. For static analysis i am using Hyperelastic test data. Now for this kind of analysis, i am planning to do frequency dependant dynamic testing with the help of DMA.

The probable outcome i am expecting from testing is loss modulus, storage modulus, frequency and uniaxial strain(preload).

Following are my doubts-

1. while giving input to software should i convert dynamic test data(loss modulus, storage modulus) to prony series?

2. At how much preload and strain amplitude, dynamic testing should be carried?

{Additional info of analysis setup -

damper of viscoelastic material is in between of two steel plate (top and base plate).

base plate is exited by an acceleration input from 1Hz to 1000Hz.

and acceleration response is taken on the top plate. that should give frequency dependent transmissibilty of rubber (i.e. isolation characteristic of rubber)}

Thanks,

Tarup,

India.

4 Replies
Jorgen
Posts: 3882
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You are asking good questions that unfortunately are difficult to answer in a general sense.
1) You can convert the DMA data to a Prony series, or you can let Abaqus (or MCalibration) do it for you.
2) That depends on your application.

The main problem with linear viscoelasticity is that it is usually only accurate at small strains.

-Jorgen

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joe hormon
Posts: 9
(@joe hormon)
Active Member
Joined: 6 years ago

Thanks Jorgen for your reply.

I have performed DMA test on MTS 831.50 x 1000Hz Elastomer Test System. Test specification was , preload- 400N(compression), frequency - 1 to 200Hz, dynamic amplitude- 1mm(peak to peak).

Probable outcome i was expecting from testing was loss modulus, storage modulus, but instead of that i am getting Elastic and loss stiffness with respective to the frequency. Is there any way to convert this output into storage and loss modulus.

Besides testing query i have some general query.

i. What are the major differences between linear and Non-linear viscoelasticity?

And ii. which test are required to find out that, the material is having linear or Non-linear viscoelasticity?

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Jorgen
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I dont know for sure, but I would guess that Elastic and loss stiffness is the same as the storage and loss moduli. Do you agree?

There are many differences between linear and non-linear viscoelasticity. One of the most important differences is that for linear viscoelasticity the stress is proportional to the strain amplitude when you perform a strain jump. This is not the case for non-linear viscoelasticity.

-Jorgen

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joe hormon
Posts: 9
(@joe hormon)
Active Member
Joined: 6 years ago

Thanks Jorgen for your reply.

I was not able to get direct output of loss modulus, storage modulus in MTS 831.50 x 1000Hz Elastomer Test System, so I tested a rubber specimen (cylinder of dia = 5mm and height 2mm) on METRAVIB DMA 50. Test specification was , preload- 10% strain (compression), frequency - 1 to 200Hz, dynamic amplitude- 5% strain. With this machine I got loss and storage modulus along with the dynamic stiffness of rubber specimen. Using these loss and storage modulus values, i analysed same size of specimen with same load condition in abaqus. I compared the analysis dynamic stiffness and testing dynamic stiffness. Analysis stiffness value is close to testing stiffness at all frequency points.

Now I want to know that if I use these loss and storage values for analysis of a component (of same material) with same preload and dynamic load, will I able to predict the dynamic stiffness?

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