# UMATH, HETVAL or DFLUX

Hello everyone,

I am new to coding user subroutines.

I have the following questions. I need to construct my own heat sources as a function of strain rates and the components of the stress tensor.

The final aim is it to code my own stress-temperature relation. For this I need the heat sources, fluxes etc... .

My geometry setting is such that each element in my geometry is deposited in a separate element set. Therefore I should be able to have access to each element separately.

My first basic question is now, how can I read in the strain rates and stress components using one of the three user subroutines:

UMATH, HETVAL or DFLUX, menaing how do I get access to these variables?

As mentioned before I have to do this for every element of my geometric object (no orphan mesh).

ciao Gunkerle

If I remember right, you cannot actually determine the strain-rate or stress from any of these subroutines since they are for purely thermal analyses. You might want to check that in the Abaqus manuals.

- Jorgen

[QUOTE=Jorgen,3322]If I remember right, you cannot actually determine the strain-rate or stress from any of these subroutines since they are for purely thermal analyses. You might want to check that in the Abaqus manuals.

- Jorgen

Hello Jorgen,

I do not want to determine the strain-rate or stress within these subroutines I want to pass the information of the values of these variables into the thermal-analysis-subroutines and then manipulate them there (e.g. using numerical integration procedures). The aim is it to constuct an integral like:

Integral (strainrate times stress)

to determine the proper internal energy and from this the rising/change of the temperature in every element.

The reason why I have to do this is that Abaqus does not provide one with a change of the internal energy due to pure viscoleastic (no plasticity involved) material behaviour (due to an answer I got from abaqus support). Therefore I need to construct my own heat sources/fluxes/internal energy changes and finally variation of the temperature due to the change in the viscoelastic part of the total energy.

I want to do this in such a way that I pass the information the strain-rates and stress from each element in my geometrical object to calculate an integral as given above to determine my New internal energy. As mentioned in my first statement every single element of my geometrical object is deposited in its own (element)-set. Thus at least I should be able to have access to all of them. I just do not know how I can pass the informations INTO this user thermal-analysys-subroutines .

Is it possible to use the routines UFIELD, UTEMP, USDFLD to accomplish this and if how could it be done?

ciao gunkerle

You might be able to do that using a USDFLD subroutine. You can feed the field variables into the other subroutines using field-dependent material parameters.

- Jorgen

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