Hi all,
I am currently using v2.22 solver.
I was trying to calibrate a material constitutive model using the deformation plasticity option in CalculiX. Per the manual section 8.33, the Ramberg-Osgood parameters are defined in terms of true (Cauchy) stress and true (logarithmic) strain, which I did.
The model is a simple cube stretched by pulling on a face by displacement BC. The displacement is 20% of the cube length, which would result in an applied engineering strain of 0.20. However, the strain output I am getting at the end of the step is 0.22. This appears to be the Lagrange strain, since the relationship:
E = 0.5*(lambda^2-1) where lambda = L/L0
This would give E=0.22 for the engineering strain of 0.2 (i.e. lambda = 1.2)
It looks like more in depth discussions about the strain types are already discussed here.
What is confusing me is the section of the manual below, which states the strain output for the deformation plasticity is the Euler strain. If the output was the Euler strain, I would expect the strain output to be ~ 0.18 (lower than the applied engineering strain level).
Could it be that the strain output type may have been changed to Lagrange strain at some point even for deformation plasticity?
More details:
Here’s the material constitutive model I am using:
*DEFORMATION PLASTICITY
70000.0,0.3,290.,14.0,4.
Output is requested here:
*El file
S, E, PEEQ, NOE
NLGEOM is not explicitly turned on by keywords, but the solution triggers it on automatically per output message.