Dear Peter,

yes you're right, you already told me this. I am using as input the following command:

/prep7

mp, ex, 1,3700 !Elastic modulus in MPa

mp,nuxy, 1,0.4 !Poisson ratio

!Define cast iron model

TB,CAST,1,,,ISOTROPIC

TBDATA,1,0.4 !Plastic poisson ratio

TB,CAST,1,1,7,TENSION !(stresses in MPa)

TBTEMP,20.

TBPT,,0,80.

TBPT,,0.007055167,82.24

TBPT,,0.00783981,84.93375

TBPT,,0.008905017,87.6605

TBPT,,0.009870315,90.3875

TBPT,,0.012339927,93.267

TBPT,,0.016915443,96.906

TB,CAST,1,1,6,COMPRESSION !(stresses in MPa)

TBTEMP,20.

TBPT,,0,40.

TBPT,,0.03855,40.95

TBPT,,0.077985,69.3

TBPT,,0.103,88.

TBPT,,0.1345,102.

TBPT,,0.155322,108.

I have another question, if you may help me. How does Ansys know when to apply the compression or tension data? I mean, how does Ansys know when the material is compressed and when it is in tension, so it can apply the correct material behaviour? I looked for this information in the Mechanical APDL help for cast iron, but they only talk about the yielding criterion used for compression and tension. The model I am working on is under a triaxial loading.

My idea was this: in a triaxial stress state, Ansys considers the principal stress with the higher magnitude, and if this principal stress is positive then that element is under tension, if the principal stress is negative there is compression. Can it be a possible explanation?

Thank you again