I want to create a custom field output in ABAQUS. For the purpose of proof on concept, I want to display the maximum shear stress as calculated from the Mohrs circle, as discussed here for a 2D shell.

I have my code below for reference:

from abaqusConstants import *
from odbAccess import *
from math import *
from copy import deepcopy
from caeModules import *
from driverUtils import executeOnCaeStartup

# ******************************************************************************
#Items in this box require student input when changing files

#must input the file path here.
odbPath = "/home/MohrsTest.odb"

odb = session.openOdb(name=odbPath, readOnly=FALSE)
odb = session.odbs[odbPath]
#this will display the instance names. Please choose one to input in line 14.
print odb.rootAssembly.instances.keys()
grout_instance = odb.rootAssembly.instances['SQUARE-1']
# ******************************************************************************
keys = odb.steps.keys()
for key in keys:
    step = odb.steps[key]
    for frame in step.frames:
        print frame.description
        Stress = frame.fieldOutputs['S']
        #try modifying scalar fields rather than creating new var element by element.
        TauMax=((S11+S22)*0.5+sqrt(power((S11-S22)/2, 2)+power(S12, 2)))-((S11+S22)*0.5-sqrt(power((S11-S22)/2, 2)+power(S12, 2)))/2
        ThetaP=(atan2(2 * S12, (S11 - S22))/2) * 180/pi
        frame.FieldOutput(name='Tau Max', description='Max Tau from Mohrs circle',field=TauMax)
        frame.FieldOutput(name='Theta P', description='Thetap as measured ccw from 0 degree',field=Thetap)
#  must re - open the output database to see the new custom field output

Abaqus throws an error immediately upon trying to calculate TauMax because of "Type Error: A float is required." However, I tried using "Tools->Field Outputs-> Create from Fields" and then created a field output in the cae for the individual frame. If I look at the replay file for this action, I can see the following code:

s1f1_S = session.odbs['/home/MohrsTest.odb'].steps['Step-1'].frames[1].fieldOutputs['S']
tmpField = (((s1f1_S.getScalarField(componentLabel="S11")+\
    componentLabel="S22"))/2, 2)+power(s1f1_S.getScalarField(
    componentLabel="S12"), 2)))-((s1f1_S.getScalarField(componentLabel="S11")+\
    componentLabel="S22"))/2, 2)+power(s1f1_S.getScalarField(
    componentLabel="S12"), 2))))/2

Thus, clearly math operations on a FieldObject must be possible. Why does my code not permit this?

I am happy to provide all .odb and .cae files for reference and verification.

  • $\begingroup$ likely atan2 doesnt like the field object. $\endgroup$
    – agentp
    Feb 2, 2018 at 12:29
  • $\begingroup$ ...note in the ABAQUS GUI operators list there is an atan but not a 2- argument atan2 . $\endgroup$
    – agentp
    Feb 2, 2018 at 16:13


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