Hi Jorgen

I am a beginner in ABAQUS and I need to simulate a tire using viscoelastic proprierties of the rubber. At first, I know the Mooney Rivlin coeficients (C01 =0.825, C10 = 0.8 and D1 = 0.012) and I have the relaxation test data (concerning t, G(t)) and frequency sweep data (concerning G,G,G* and freq.). However I do not know how could a set the long term modulus in the input file of ABAQUS.

I mean , if I write

*HYPERELASTIC, MODULI=LONG TERM,MOONEY-RIVLIN

0.825,0.8,0.0122

*VISCOELASTIC,TIME=FREQUENCY DATA

G1/Ginf , 1-G1/Ginf,,,freq1

G2/Ginf , 1-G2/Ginf,,,freq2

G3/Ginf , 1-G3/Ginf,,,freq3

Gk/Ginf , 1-Gk/Ginf,,,freqk

where the Ginf = long term modulus

But how can I find the value of Ginf to calculate G/Ginf and G/Ginf ?

If I write MODULI=INSTANTANEOUS instead of MODULI=LONG TERM, how could I calculate Ginf and consequently G/Ginf and G/Ginf?

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I tried to change the input file writing:

*HYPERELASTIC, MODULI=LONG TERM,MOONEY-RIVLIN

0.825,0.8,0.0122

*VISCOELASTIC,TIME=RELAXATION TEST DATA

*SHEAR TEST DATA,SHRINF = ratiog

gr1 , t1

gr2 , t2

gr3 , t3

grk , tk

where grk = G*(tk)/G(0) and ratiog = Ginf/G0

Usually,the value of Ginf can be found in the relaxation test data (it is the last measured point or interpolated after the last point) and G0 is the G(t=0), but if everything is normalized by G0, I must inform the G0, mustnt I ? How could I do that.

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For this material, as I had told, I have both the Sweep Frequency Test Data and a Relaxation Test Data. The problem is when a run a dynamic analysis model (first using the Sweep Frequency Data and after, in the same model, using the Relaxation Test Data), there a considerable difference between the responses (strain, stress, displacements, damping ...etc)

To simulate both tests , i made a virtual specimen with the same geometry of the real one and simulated a relaxation test. I noted when I used the option TIME=FREQUENCY DATA, the simulated specimen relaxed so fast and when I used the TIME=RELAXATION TEST DATA, the same specimen relaxed so long as similar as the same Relaxation Test.

My doubt is , when I set the viscoelastic properties in the ABAQUS, independent of the option (TIME = FREQUENCY DATA or RELAXATION TEST DATA), mustnt the viscoelastic properties be the same ? For both cases, Abaqus estimates the PRONY Series Coefficients that define the viscoelasticity in frequency domain and the viscoelasticity in time domain !

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I hope you understand my doubt !

Could you indicate me a good and easy Literature ?

Thank you very much !

Best Regards

ThiagoSaccheto

(mechanical engineering)