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ANSYS Prony series from shear modulus vs. frequency

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Posts: 2
Topic starter
(@ricejr)
New Member
Joined: 16 years ago

Folks,

I have loss and storage moduli vs. frequency.

Freq(Hz) Storage Modulus (MPa)

0.1 649.284

0.2 679.789

0.5 725.454

1 762.565

2 794.796

5 837.495

10 864.113

20 889.855

50 920.256

100 939.799

How can I define a Prony series using this data within ANSYS since the software asks for loss modulus vs. time (should I input 1/ frequency in Time Column in Ansys)? Can I define an Ogden model based on Prony series?

Thank you...

6 Replies
Posts: 3998
(@jorgen)
Member
Joined: 4 years ago

Actually, I think that ANSYS asks for the shear modulus and the bulk modulus as a function of relaxation time. That data set is then used to calculate the Prony series for the material.

Some FE software (e.g. ABAQUS) also allows for the experimental data in the form of storage modulus and loss modulus as a function of frequency. The FE software then internally calculates the Prony series from the given frequency data.

If ANSYS does not allow for experimental data in frequency format, then you will need to convert your data to a Prony series yourself. You cannot input 1/freq data.

I wrote a short description on how to do that conversion in the following [URL= https://polymerfem.com/polymer_files/Prony_Series_Conversion.pdf ]paper[/URL].

- Jorgen

6 Replies
Posts: 2
Topic starter
(@ricejr)
New Member
Joined: 16 years ago

Jorgen

Thank you Jorgen,

I was afraid of your answer...I neded to be sure, since their manual is not that clear. I worked with Ansys for 10 years, and they always do things a bit differently (see piezo input matrices).

I have those curve fitting algorithms from my Ph.D. days.

Regards and thanks...

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Posts: 2
(@DineshDK)
New Member
Joined: 15 years ago

Reason

Can you pl tell me why we cant use 1/frequency for time in ANSYS modeling. I am currently studying the viscoelastic behavior of Photo resists, and trying to incorporate in the warpage modeling.

We performed experiments using DMA and have got the details of storage n loss modulus with respect to frequency. I need to develop prony series from this. Can you pl why 1/frequency is not time that is the input variable for ANSYS and if 1/f is not time, can you pl tell how to find the time that is required to be input in ANSYS?

Thanks

Rgds,

Sathyanarayanan

RA, GA tech.

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Posts: 2
(@DineshDK)
New Member
Joined: 15 years ago

Query

I found the relaxation time tou = 1/(tan delta x omega), is this the value that is required for ANSYS?

Sathyanarayanan

RA

GA Tech

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Posts: 1
(@kompozits)
New Member
Joined: 15 years ago

how can we get and use of data in ANSYS plz give detail procedure/method

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Posts: 1
(@MedTrust)
New Member
Joined: 9 years ago

how to evaluate storage and loss moduli in ansys

hi, could you please help me how to evaluate storage and loss moduli in ansys,if possible please send an example in ansys

[QUOTE=alex,2728]Folks,

I have loss and storage moduli vs. frequency.

Freq(Hz) Storage Modulus (MPa)

0.1 649.284

0.2 679.789

0.5 725.454

1 762.565

2 794.796

5 837.495

10 864.113

20 889.855

50 920.256

100 939.799

How can I define a Prony series using this data within ANSYS since the software asks for loss modulus vs. time (should I input 1/ frequency in Time Column in Ansys)? Can I define an Ogden model based on Prony series?

Thank you...

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