hysteresis effect

[dermicha29]

dear all,

i´m using the neo-hookean model (hyperelastic) with hybrid elements and a coefficient D1=0 for simulating a fully incompressible elastomer specimen under large deformations. i would like to consider the hysteresis effekt as well but there are allways the following errors:

"Hysteresis material calculations did not converge for 144 elements at one or more integration points. The elements have been identified in element set warnelemhysteresisstep1inc1.

No convergence in computing elastic jacobians or stretches at 1152 points. Also, material instability may have been detected. Only the first 100 have been reported above"

can anybody help me on this subject?

thanks in advance

michael freund
university of hannover
Germany

[Jorgen]

- What element type do you use?
- Does it work better if you take smaller time increments?
- Does it work better if you make D1 > 0 (that is make the material slightly compressible)?
- How large strain can you reach before you get the error?

I have developed my own UMAT implementation of the *Hysteresis model. My implementation is for most cases more stable and robust than the built-in model in ABAQUS. If you cannot get the built-in hysteresis model to work well enough then my UMAT implementation (which is commercially available (http://www.polymerfem.com/modules.php?name=User_Subroutines)) would be a great option.

- Jorgen