Hi All,

I would like to use Abaqus to model the viscoelastic material behaviour of a polymer (test run to see how it works).

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 Ihave to specify the normalized bulk jk(t) and normalized shear compliance js(t).

js(t)=G0Js(t), jk(t)=K0Jk(t)

where Js is the shear compliance and Jk the volumetric compliance

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

J(t)=epsilon(t)/sigma0 where sigma0=F/A0

J(t) then is the inverse of a time-dependent elastic modulus: 1/E(t)

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

1/G(t)=2(1+v)*1/E(t) where 1/G would be the shear compliance Js and v the Poissons ratio

1/K(t)=3(1-2v)*1/E(t) where 1/K would be the volumetric compliance Jk.

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 Im 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?

Thanks,

Andreas