Abaqus: coordinate transformation in cae and via python yield different results

Hi,

I am analyzing a very simple model of an hollow cylinder which is subjected to torsion in Abaqus 6.13-1.

I am interested in the stresses of one node (node 13) in my model. 

 

Using Cae I get the following results:

s13@node13 (cartesian coordinate system) = -17.2586250

s23@node13 (cylindric coordinate system) =    17.2586250

 

But using python to query the stresses i get:

s13@node13 (cartesian coordinate system) =  -17.2586250305176

s23@node13 (cylindric coordinate system) =    17.2585487365723

 

This is how I get my results in python:

myOdb = openOdb('Job-1_py.odb') 

myDatumCsys = myOdb.rootAssembly.datumCsyses[name_of_datum_csys]  #my cylindric coordinate system

myStep = myOdb.steps[name_of_step]

myFrame = myStep.frames[-1]

myFieldOutput_S  = myFrame.fieldOutputs['S']

myFieldOutput_S_transformed  = myFieldOutput_S.getTransformedField(datumCsys=myDatumCsys)

mySubset_from_Set_A = myFieldOutput_S.getSubset(region=myNode_A,position=ELEMENT_NODAL)

mySubset_from_Set_A_transformed = myFieldOutput_S_transformed.getSubset(region=myNode_A,position=ELEMENT_NODAL)

The results are in    mySubset_from_Set_A_transformed. values

 

Can anyone tell me why there is a difference in s23@node13 (cylindric coordinate system) between cae and python?

 

Thank you very much.