TNM for Celcon-M90

[Vinod Kumar mannaru]

Hello,

I am using TNM to simulate Celcon-M90 material, calibration shown good fit with experiemental data (Uniaxial tensile data). Results (ANSYS) shows huge stresses in the order of ~320MPa and equivalent plastic strain of '0', however the max/break point in the experimental data is at ~67MPa. Analysis has simple compression loading, however the critical region of interest is in tension that made me convince to use uniaxial tensile data (I don't have any other experimental data). When I rerun the analysis with elasto-plastic model, I could see max equivalent stress as ~77MPa. Is there something going wrong in the analysis? Can anyone help me to interpret the results?

Thanks in advance,
Vinod Kumar

[Jobie.Gerken]

Vinod,

You don't give many details about the simulation or material model. However, I suspect your large stress relative to your "break point" stress is due to pressure. You can try looking at the deviatoric stresses or von Mises stress to see if this is the case. If this is the case, remember that in Ansys MAPDL the Bergstrom-Boyce model has a pressure-volume relationship that is linear in the volume ratio (if it's not incompressible). This means the pressure can increase without bound and it does not affect the behavior of the BB model.

Large pressures can be caused by triaxial constraints in your simulation or can be caused by numerical errors in the solution. Numerical errors in a converged solution are not common but can be caused if you overconstrain the pressure degrees of freedom - this is common for very simple simulations (eg, 1 element uniaxial simulation) that are sometimes used to investigate the behavior of the material model. See the discussion about mixed u-P formulations and overconstraint in the Theory and Element references.

Jobie

[Jorgen]

Vinod, Can you provide the experimental data file(s) and the TNM material parameters. And if you used MCalibration, also the mcal-file.
If you cannot provide them for everyone on this forum, feel free to send them directly to me (and if you want Jobie).

-Jorgen