Discussion Forum

I have the same question with you!

The viscoelastic Prony series constants (Gi and Ti) should be evaluated from a creep test using nonlinear least-square curve fitting. Your polymer's stress-strain response will determine whether a viscoelastic material model is more suitable than a hyperelastic one, or if a more advanced material model is required.

Nagi Elabbasi
Veryst Engineering

In case of viscoelastic material, the problem is almonst same. I’m in trouble with calculating instantaneous shear modulus and relaxation time for Generalized Maxwell Model. For example I would use viscoelastic material where Young modulus E = 8e10 Pal, Poison’s ratio v = 0.25, viscosity nu = 1e18 Pa s. From this I calculated total shear modulus G = E/{2(1+v)}, bulk modulud K =E/{3(1-2v)} at the first load limit and Maxwell relaxation time Lamda = nu/G.

Now how can I calculate instantaneous shear modulus and corresponding relaxation time for Generalized Maxwell Model?


--
Md. Tariqul Islam
Department of Earth Science
University of Gothenburg, Sweden
tariqul.islam@gvc.gu.se

Hi Tariqul! Which kind of problem are you attempting to simulate?

Hi Fabio,

I'm interested about Plate spreading model. If you have something to share please, knock me. Thanks.

Regards
Tariqul
-------------------
Md. Tariqul Islam
Department of Earth Science
University of Gothenburg, Sweden
tariqul.islam@gvc.gu.se

I am having trouble with modeling fluid flow over a viscoelastic material. The material doesnt seem to deform or show visco elastic deformation. Can someone please take a look at the model and tell me whats wrong? I am relatively new in COMSOL,

I tried constraining one side of the solid sphere but still it doesnt show any deformation. I think the object is behaving like a linearly elastic model although it has been over ridden with visco elastic model. Can you please suggest what is wrong? Why is it not deforming? (what are proper parameters which will make it deform?)

The relaxation time that you used for the viscoelastic term is very large 1e30. That effectively cancels the viscoelasticity except in a time frame of comparable magnitude to 1e30 seconds. The viscoelastic shear modulus is also much smaller than the long term shear modulus. If you set the Maxwell shear modulus = 1000[Pa], and relaxation time = 2[s] you should see the solution changing with time.

Nagi Elabbasi
Veryst Engineering

Hello,

I am trying to model a volcano with viscoelastic material. But I cannot find the linear viscoelastic material mode option in my interface (solid mechanics(solid)>material mode>). I am using COMSOL 5.0. Can you help me with it.

Bhuvan.

Hello Bhuvan,
Viscoelastic materials are available only if your license includes the Structural Mechanics Module. They are not available among the structural mechanics capabilities of the core COMSOL Multiphysics. More options are available if your license includes both the Structural Mechanics Module and the Nonlinear Structural Materials Module. See the attached exerpt from the online product specification chart (www.comsol.com/products/specifications/),
To determine whether your license includes either of those products, go to File > Used and Licensed Products.
Best,
Jeff

Dear Aseem,

I am also trying to use viscoelastic materials in COMSOL. But I only found the one material type named "linear viscoelastic materials" under the "solid mechanics" category (COMSOL 5.2). I wonder could you please tell me where is the viscoelastic material type whose inputs are Prony parameters Gi and Ti? Many thanks.

Best regards

Hai