# Stiffness interpolation with field variables

Dear all,

Im trying to evaluate my material modell doing some single element tests. The stiffness of my material depends on 6 field variables, used to degradate the the materials stiffness after a the occurence of failure. Therefore the values of FV are calculated in a USDFLD subroutine.

And now my problem: Even though my FV-Values offer CONSTANT values, the stiffness is wrong as they vary over the time. How can that be? Abaqus shouldnt interpolate any stiffness, so there should be constant stiffness values, too.

But perhaps Im just wrong calculating my materials stiffness by simply dividing stresses through strains at the integration points?! I thought, that must be right looking at the analysis manual, chapter 18.2.1 (defining orthotropic elasticity by specifying the engineering constants).

So what can I do? Where is the problem in the linking between stiffnesses and field variables FV?

Thanks a lot!!

Carol

The problem is solved. I can only say: Better calculate the stiffnesses just the way it is written in the manual.... Of course, I cannot just divide stresses through strains (only for shear modulus).

ðŸ™„

yield point in USDFLD

HELLO, all

Iam a post graduate engineer, i model a soft clay in braced excavation applications,

i need to define the yield point in usdfld,

my plasticity model is extended drucker and prager model. How can i define the yield point in the usdfld to change the soil modulus after yielding.

best regards

I dont use the Drucker-Prager model so I dont know for sure, but you may be able to make your material parameters dependent on the field variable that you calculate in the USDFLD routine. That may solve your problem.

-Jorgen

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