Using SOFA to simulate Viscoelastic Behaviour

[Pasquale94]

Hello Everyone.
I am currently using for my research Sofa in Hyperelastic force field, and I find it very accurate.
But in future I will evolve my research treating viscoelastic material and so modeling the viscoelasticity.

There are viscoelastic models or Force fields in Sofa? Can you talk me about all the possibilities?

Thanks in advance!
Pasquale

[Hugo]

Hi @pasquale94

You can add Rayleigh damping which will mimic damping, i.e. viscosity based on Mass and Stiffness matrices.
You can also see :
– UniformVelocityDampingForceField
– and DiagonalVelocityDampingForceField

Do you have an idea of damping model you would be looking for?
Best wishes,

Hugo

[Pasquale94]

Hello @hugo,

I explain a bit how I am conducting my research.

I am basically demostrating on how the soft robotic controllers can be more accurate if we have a good model of the material that we generally use… Also because as you might know, I am working for particular materials.

For a kinematic control, i started from static test on my material (unaxial, shear test and so on), so for now the effect of viscosity in static condition is not so relevant, so i choose to model my material as an hyperelastic one. So i produced experimental data (mechanical test) fitted the curve in Abaqus and retrieve the constitutive law with material constant… Put everything in sofa and make the controller and so on.

Then, I want to pass to build a dynamic controller, so i need the dynamical behaviour of my material, uder creep and stress relaxation test for example. The material scientists working with me already know that our materials have a viscoelastic nature if it undergoes into dynamic test.

In abaqus, for the dynamic responce modeling of my material I have introduce the hyperelastic model already calculated from static test plus the creep test experimental data to calculate the viscoelastic calculation.

Then Abaqus made the fitting for viscoelastic parameters, basically he build a Prony series.

or if I use the stress relaxation test instead of a creep test, abaqus can make the Maxwell modeling parameter simulation.

So, I am asking, if it is possible to enter to define viscoelasticity of my material or using prony series parameters or Maxwell modeling. (Actually the maxwell modeling is such a mass spring-damping system, so i think that you Damping solution is near to the maxwell modeling of viscoelasticity).

I hope that is clear. Thanks you in advance. I link you wikipedia page about viscoelasticity to understand of what I am talking about.

[Hugo]

Hi @pasquale94

It’s been a long time I have not read about Prony series and Maxwell model!
In SOFA:
– the hyperelastic material is only in charge of the hyper-elastic forces and no damping is added
– no component is implementing damping based on Prony series to my best knowledge
– I think something that could be close to Maxwell modeling would be the Rayleigh stiffness damping coefficient
– finally, nothing prevent from implementing a new damping forcefield integrating in each finite element the damping model you would like

Let me know if this helps.
Best

Hugo

[Pasquale94]

Yes, i would like for example to add a Maxwell modeling to the Hyperelastic forcefield , to have the kinematic and Dynamic modeling of the material working toghether.
Is this possibile to add such Mass -spring – dumping model to my forcefield?

For example introducing a variabile “viscolelasticity” in the force field?

Thanks a lot for the answer Hugo!.

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