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Time domain testing of viscoelastic material in Abaqus

Dear All;

Hope you are having a wonderful day. I am currently working on a project which is related to developing a user material interface for a viscoelastic material, for testing it I have to compare it with the existing built-in Abaqus model. Since my working is on small strain deformation I am using time-domain in Abaqus. I have the bulk modulus of the material "K", Young's Modulus of the Material "E", the shear moduli for Prony series "mu1", "mu2" and "mu3" and the relaxation times "tau1" AND "tau2". I need to convert this data into Abaqus input mode which so I need "g(i)p", "k(i)p" and "tau(i)". I know that according to equations:

K=E/3(1-2v), mu(infinity)=E/2(1+v) and mu(i)=mu(infinity)*g(i)p

will give me the values for Poisson's ratio "v" and values for "g(i)p" but can someone please guide me how to find the bulk moduli and relaxation times. I do not have test data for the material unfortunately and I have been trying to locate any conversion formulation from books or papers. 


Thanking you in advance for helping.


Best Regards;

Asim Gillani 


Frank Richter's picture

Look up the BAQUS example 2.1.1
'Viscoelastic rod subjected to constant axial load'


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Dear Sir;

Thank you so much for your kind response. I will surely join the blogs and groups mentioned. 

Best Regards;

Asim Gillani 


Dear Sir;

I have read the example you mentioned and it does explain how to convert certain data available for UMAT to ABAQUS input data but it does not give information on finding bulk moduli k(i)p, I have searched on different forums and what I have found is that if Poisson's ratio is 0.49~0.5 the k(i)p values are zero (not mentioned) which is true for the example listed. but if the Poisson's ratio is not within this range then how do we calculate k(i)p from conversion from above-mentioned data. Further, I have tried searching for the reference listed in the example "Collingwood et al. (1985)" but I am unable to find it. Could you please kindly provide guidance in this matter. thanking you in advance.


Best Regards;

Asim Gillani

Frank Richter's picture

I also wanted to get this manual into my hands. The german Abaqus HQ forwarded to me an e-mail from Abaqus World HQ:

"The bench mark problem is simply a clone of the first example problems in the second volume of TEXVISC user's manual. Besides the example problems, the manual only describes how to use the program. There is nothing noteworthy to make a copy. TEXVISC is a 2D finite element program for thermal and mechanical analysis."

So, forget it.


It is bizarre to declare a simulation correct simply on the grounds that some other FE program is declared correct.


Consult the forum.

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