Using Mooney-Rivlin model for hyperelastic materials

Anonymous · ‎03-15-2018

Hi, I am trying to do some simulation of constrained buckling of a hyperelastic material sheet. I started form a butyl rubber and modified the physical properties by adding hyperelastic behavior using the Mooney-Rivling model. The problem I have is that I can change the first two parameters A1 and A2, but the value of the third parameter D1 cannot be changed and is fixed at D1=(A1+A2)* 10^3 (making the material essentially incompressible).

With the parameters I am using, A1=100000 Pa, A2=339000 Pa (which I obtained from a publication on coefficients estimation for rubber, so I expect them to be more or less acceptable), this gives a value of D1 ~ 4*10e8 Pa, and the simulation complains about this value before throwing an error and crashing.

Can you help?

Thanks

Marco

ahreum.ryu · ‎03-15-2018

Hi @Anonymous,

Thank you for your posting!

I tested it with my sample model so I think the material information seems to be ok.

Are you working on the verification model of nonlinear which have the "Warning: NO CONVERGENCE IN MAXIMUM NUMBER OF ITERATIONS PERMITTED" error?

(If yes, you got the simulation support ticket and I'm working on it)

Could you confirm whether my information I have is correct?

I look forward to your reply

Many thanks,

Ahreum.

Ahreum Ryu

Product Support Specialist

My Screencasts | Fusion 360 Webinars | Tips and Best Practices | Troubleshooting

Anonymous · ‎03-16-2018

HI Ahreum,

Thanks again for the support.

I answered to your private email trying to give you some more information, but yes, I do get a "Warning: NO CONVERGENCE IN MAXIMUM NUMBER OF ITERATIONS PERMITTED" error. But to keep to the subject of the post, why can't I change the parameter D1 in the Mooney-Rivlin model? I know for sure that it was possible in the past - there is a post where somebody mentioned that he/she set it to a specific value. Why can't I change it? Apart of maybe being (or not) relevant to my simulation failures, it is important to be able to change this parameter to allow for compressible materials.

Cheers

Marco

Anonymous · ‎03-19-2018

Hi @Anonymous

What you are seeing is a small UI bug that is a known issue. The expression can be deleted, but the highlighting doesn't go away and you cannot enter 0. To work around this, just highlight the whole expression and then start typing the values you want to enter. If this does not work, please let me know, but I am able to enter values for D1.

Further, once you enter your material properties as desired, assuming the above works for you, if you are still encountering issues with convergence in Nonlinear Static Stress, you may want to consider the Event Simulation study type. Event Simulation is a transient study that is well suited for very short duration, highly dynamic events. This will likely converge better if you expect a very dynamic response to your loading condition.

I hope this helps. Let us know if you continue to have problems.

Thanks,

Mike Smell

Product Manager, Fusion 360 - Simulation

Anonymous · ‎03-21-2018

Hi Mike,

thanks for the help. Yes now it works as you describe. When I raised the problem it wouldn't "hold the edit" and jump back to the default formula. Probably a glitch on my side..

I already tried the event simulation, but that also crashes.. I hope it's something I'm doing wrong, but I don't understand how to fix it. Now I am simplifying the problem (I am removing the "top" constraining block - the one not touching the plate) trying to isolate the bug(s) but till now I still have failed simulations.

I have just rerun a nonlinear static stress on the simplified model (attached), and it failed with the following details:

unconstrained_hyperelastic_plate_buckling v4: Simulation Model 1 - Study 1 - Nonlinear Static Stress
_____ 2018-03-21 13:47:50 _____

unconstrained_hyperelastic_plate_buckling v4: Simulation Model 1 - Study 1 - Nonlinear Static Stress
_____ 2018-03-21 13:47:50 _____
Job has finished successfully. Receiving results.

unconstrained_hyperelastic_plate_buckling v4: Simulation Model 1 - Study 1 - Nonlinear Static Stress
_____ 2018-03-21 14:00:59 _____

unconstrained_hyperelastic_plate_buckling v4: Simulation Model 1 - Study 1 - Nonlinear Static Stress
_____ 2018-03-21 14:00:59 _____
7912 Tetrahedra : 100.0% of elements (100.0% of volume)
       Face Angle min: 4.2, max : 171
       Dihedral Angle min: 3.45, max : 173
       Worst shape ratio : 29.3 on element 1537
       Worst aspect ratio : 13.5 on element 355, shortest edge: 0.005, longest : 0.0773
       Lowest collapse ratio : 0.0516 on element 1537
       Worst Jacobian ratio : 1 on element 1
Base mesh: 14959 nodes, 7912 elements
Job has finished successfully. Receiving results.

unconstrained_hyperelastic_plate_buckling v4: Simulation Model 1 - Study 1 - Nonlinear Static Stress
_____ 2018-03-21 14:01:27 _____

unconstrained_hyperelastic_plate_buckling v4: Simulation Model 1 - Study 1 - Nonlinear Static Stress
_____ 2018-03-21 14:01:27 _____
635291 Tetrahedra : 100.0% of elements (100.0% of volume)
       Face Angle min: 12.8, max : 146
       Dihedral Angle min: 10.4, max : 159
       Worst shape ratio : 8.46 on element 63008
       Worst aspect ratio : 4.64 on element 7457, shortest edge: 0.00227, longest : 0.0201
       Lowest collapse ratio : 0.173 on element 63008
       Worst Jacobian ratio : 1 on element 1
Base mesh: 943277 nodes, 635291 elements
Job has finished successfully. Receiving results.

unconstrained_hyperelastic_plate_buckling v4: Simulation Model 1 - Study 1 - Nonlinear Static Stress
_____ 2018-03-21 14:04:56 _____

unconstrained_hyperelastic_plate_buckling v4: Simulation Model 1 - Study 1 - Nonlinear Static Stress
_____ 2018-03-21 14:04:57 _____
Document is being uploaded to cloud storage. Cloud job is pending.
Scheduling job.
Job scheduled successfully.
685686 Tetrahedra : 100.0% of elements (100.0% of volume)
       Face Angle min: 13.3, max : 135
       Dihedral Angle min: 12.7, max : 154
       Worst shape ratio : 6.9 on element 56740
       Worst aspect ratio : 4.2 on element 36831, shortest edge: 0.00227, longest : 0.0201
       Lowest collapse ratio : 0.206 on element 114767
       Worst Jacobian ratio : 1 on element 1
Base mesh: 1027448 nodes, 685686 elements
Solver mesh: 1027448 nodes, 685686 elements
Job has finished with errors. Receiving results.
Error: INSUFFICIENT ELEMENT STORAGE SPACE ALLOCATED
Cause : The number of internal elements generated exceeded the space allocated. This error will
              occur during the generation of slide line or surface contact segments if the
              MAXADJEDGE model parameter is set too low. The default AUTO setting will set
              MAXADJEDGE to 50 if SLINEMAXACTDIST is set to AUTO, and zero if set otherwise. A zero
              setting will attempt to allocate the required space but may overestimate the storage
              requirement and result in an S1110 memory allocation error.
Action : Increase the MAXADJEDGE setting in increments of 10.
Error: Solver Error
Error: An error occurred while solving the model.

Now, if I knew how to change the MAXADJEDGE parameter I could try to change it.. but actually this cannot be changed (http://help.autodesk.com/view/fusion360/ENU/?caas=caas/sfdcarticles/sfdcarticles/How-to-change-a-sim... ) so I don't know what to do..

I will now try with an event simulation and report the results.

Thanks

Marco

weltin2MMEW · ‎03-01-2021

Hi There

me too I want to simulate rubber loading unfortunately I am unexperienced in creating material models for Fusion360. How can I create my material model usig teh Mooney parameters i found? Material is natural rubber with a shore hardness of 50Sh(A). Hope you can help. KR Uwe Weltin