Learning Forum

[yspradhan]

Hello Everyone,

I am working to solve a hyperelastic model under bending dominated displacement loading. I am using solid 186 elements. The solution converges well but structure shows excessive stiffness. I tried the mesh refinement, full and reduced integration schemes and displacement as well as u-P formulation. I continue to get the response that is unrealistically stiff.

I would like to get your inputs on how best we can resolve this.

Sincere Regards,

Yadnyesh

[peteroznewman]

Please insert an image of the mesh.
What order are the elements: Linear or Quadratic?
How many elements are there across the thickness?
What shape are the elements Tet or Hex?

[yspradhan]

Thanks Peter for your response. Please find the images below
Attaching the stiffness calculations in the subsequent post.

[yspradhan]

Material input data is the stress-strain curve from ANSYS material database. Rest of the curves are the predicted responses from the FE model, Any further assistance on this will be greatly appreciated.

[peteroznewman]

Please show the material input data.
I assume you turned on Large Deflection.

[yspradhan]

I could figure it out. This is primarily because of the material model used for fitting the measured stress strain curve. ANSYS sample material data of Neoprene Rubber uses the Neo-Hookean model for fitting the data. It uses the initial shear modulus of 0.0271 MPa. (Note that the stress strain material input data given in the previous chart is the measured uniaxial stress vs strain curve) This value pretty much matches with the predicted shear modulus of the structure. The predicted shear stress vs strain curve is given below that has shear modulus in the range of 0.0273 MPa that stiffens to around 0.034 MPa towards the end of the loading. This explains the stiffness behavior of the model that is consistent with the input data and the material model used. It may be worthwhile to check if better results can be obtained by using some alternative material model.

Thanks for your responses that really made me review the model really critically.