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# Deviatoric strain output

## Deviatoric strain output

(OP)
Hi guys,

I am facing the following problem:
I want to obtain the maximum value of deviatoric strain at each integration point during a certain step in my simulation.
Is this possible without the usage of any subroutine (I was thinking about output from fields/output from frames)? If so, could you explain me how to obtain deviatoric strain as an output in abaqus and especially how to obtain the maximum value of deviatoric strain during a whole step?

I guess it should be possible somehow via the 'create output from fields'-feature, but I cannot figure out how to exactly calculate it.

The material model that I am using is just linear elastic.

### RE: Deviatoric strain output

Unfortunately deviatoric strain is not available as a predefined output variable in Abaqus. But you should be able to use the data generated by the software and calculate deviatoric strain which is given by the following formula:

e = ε - (1/3) tr(ε) I

Basic arithmetical operations on field output data can be performed using Create Field Output --> From Fields. List of available operations may be found in the "Overwiev on operations on field output" chapter of the Abaqus/CAE User's Manual). For more advanced computations Abaqus/CAE won't be enough.

### RE: Deviatoric strain output

(OP)

I am struggling with implementing that formula in the field ouput 'formula line'. I cannot simply put the identity matrix 'I' in there, so then how to substract the hydrostatic part from the whole strain tensor?

### RE: Deviatoric strain output

Say an example to generate the hydrostatic pressure:

(s1f1_S.getScalarField(componentLabel="S11")+s1f1_S.getScalarField(componentLabel="S22")+s1f1_S.getScalarField(componentLabel="S33"))/3
(You can use this in Python also or directly in the GUI of ABAQUS/CAE, Create - > Field Output ..)

So to get the deviatoric 11 stress component: s1f1_S.getScalarField(componentLabel="S11") - the hydrostatic pressure shown above.

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