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Viscoelasticity in Abaqus

Hi All,

 I would like to use Abaqus to model the viscoelastic material  behaviour of a polymer.

I have material data from a simple uniaxial creep experiment (nominal strain vs time).  I tried to use the viscoelastic material model in Abaqus.  I am a bit confused as to how I need to enter my data (what format). 

The manual says I have to specify the normalized bulk and normalized shear compliance


where is the shear compliance and the volumetric compliance


Is it correct if I use my strain to calculate the creep compliance, which is defined as:


    then is the inverse of a "time-dependent elastic modulus":

And then to get the shear and volumetric compliance, is it valid to use the following equations:


where would be the shear compliance and

the Poisson's ratio

where would be the volumetric compliance .

Now according to the manual I have to calculate the normalized shear and bulk compliance by multiplying the values by G0 and K0, respectively.  That part I'm not really understanding... I guess G0 and K0 are the initial shear and bulk modulus, respectively.  To get them I need to again use the above equations (G=E/2(1+v) and K=E/3(1-2v)) and use the initial elastic modulus, which I can get from the initial elastic deformation. 

What confuses me is that the shear and bulk compliance are supposed to be 1 at t=0.

All of the above of course assumes linear viscoelasticity... What if it is not linear??

Does anyone have any hints or comments about my approach?








I've never used the built-in visco-elastic model in Abaqus, so I cannot be much of a help. I looked up that portion of the manual, but obviously I don't see anything you do not.

I think what you need to do really is to divide by the initial values. That gives you normalized values, but scaling them so that a certain value (in this case, the initial value) is 1. This sort of normalization is employed in many engineering problems.

Abaqus does not have built-in, nonlinear viscoelastic models (to the best of my knowledge). To perform a simulation with nonlinear viscoelasticity, you would need to use a UMAT user subroutine to define the material behaviour for Abaqus.


Good luck!

Aaron Goh's picture


This has been discussed before:check out this thread:


ABAQUS does have a user-friendly way of modelling non-linear viscoelasticity.


thanks for the link Aaron


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