July 29, 2019 at 4:46 pmansysuserSubscriber
I understand the latest versions of ANSYS no longer allow the user to create a custom material model by modifying the USERMAT.f template. What options are there for doing this as alternatives? I know that Engineering Data has many material models, but the model I need to implement is not listed there. Can it be done through USERELEM.f or is there a preferred method to this?
July 29, 2019 at 5:38 pm
July 29, 2019 at 10:18 pmansysuserSubscriber
Thanks SandeepMedikonda! That is great news.
I am a bit confused on where to put the code for my own simulation. I am modeling an active stress such as found in a muscle contraction. In this formulation the total stress is broken into components like this: TotalStress = PassiveStress + ActiveStress. The passive stress is due to the material model alone and the active stress is a function of time.
Would I program this into the USERMAT or would it be better to put it into USERELEM? Or do I need to do both, with the USERMAT only accounting for the passive stress component? I want to know the recommended way to accomplish this, since it seems simpler to implement USERMAT and add the active component as long as I have access to the time variable i.e., the current simulation time.
July 30, 2019 at 5:43 pmSandeep MedikondaAnsys Employee
Please refer to Section 2.4: Subroutines for Customizing Material Behavior of the Programmers Reference
There is also an example in Appendix C of the same guide:
I am not sure how you are dividing the total stress into active and passive components, I haven't come across anyone trying to do this...Either way any operations on the material response should come from the constitutive response....
July 30, 2019 at 6:11 pmansysuserSubscriber
Thank you for the example, SandeepMedikonda.
The division of stress into active and passive components is a common practice in the biophysics modeling field. For just a few examples are posted below: Many researchers have used Abaqus for this, but I am interested in doing the same thing with ANSYS. So it sounds like you are saying it is better to put this into USERMAT than to try to add to a custom element via USERELEM? PLEASE confirm. Thanks
Johansson, T., Meier, P. and Blickhan, R., 2000. A finite-element model for the mechanical analysis of skeletal muscles. Journal of theoretical biology, 206(1), pp.131-149.
Baillargeon, B., Rebelo, N., Fox, D.D., Taylor, R.L. and Kuhl, E., 2014. The living heart project: a robust and integrative simulator for human heart function. European Journal of Mechanics-A/Solids, 48, pp.38-47.
Muehlhausen, M., Janoske, U., & Oertel, H. (2015). Implicit Partitioned Cardiovascular Fluid–Structure Interaction of the Heart Cycle Using Non-newtonian Fluid Properties and Orthotropic Material Behavior. Cardiovascular Engineering And Technology, 6(1), 8-18.
Shavik, S.M., Jiang, Z., Baek, S. and Lee, L.C., 2018. High spatial resolution multi-organ finite element modeling of ventricular-arterial coupling. Frontiers in physiology, 9, p.119.
July 30, 2019 at 8:40 pmSandeep MedikondaAnsys Employee
I briefly skimmed through the first paper:
It looks like they're implementing this without using the usermat. That paper describes the procedure, it's not a standard procedure so we don't support it for commercial customers too. You would have to follow the paper and implement it and ask us specific questions.
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