Viscoelastic problem with UMAT

[zouyu00]

I've developed the UMAT for a viscoelastic material. However, when simulating the stress relaxation test, I have a question of the input file.

For the material, I just use

*Material, name=Material-1
*Depvar
12,
*User Material, constants=12
0,0,.....

And in the step period,

*STEP,NLGEOM,INC=1000000
*VISCO,CETOL=0.05
1E-5,2000,1E-10,20
**

However, the dat file reported the error of:
***WARNING: A VISCO ANALYSIS IS NOT MEANINGFUL SINCE THERE ARE NO MATERIAL
DATA FOR CREEP, SWELLING, VISCOELASTICITY OR VISCOUS


My question is how to link my UMAT to the visco analysis of stress relaxation test? Should I use other keywords?

Thanks very much!


Yu Zou

[Jorgen]

If you use a UMAT then you should use the *Static keyword.

-Jorgen