Abaqus FEM simulation of Pneunet Actuator

[sevs]

Hi guys, I'd like some help with a simulation of a flexible actuator. When I start the job after a while I get 3 errors like this: "INCOMPRESSIBLE HYPERELASTIC MATERIALS CAN ONLY BE USED WITH HYBRID, PLANE STRESS, OR 1D ELEMENTS." and the simulation doesn't run.

What I couldn't understand is that when creating the mesh I'm setting the element as a hybrid, I'll put a screenshot of the configuration here.

Thanks for the help!

 

[FEA way]

It’s Abaqus/Standard analysis, right ? Use Query or check the input file to make sure that all elemenets are hybrid.

 

[sevs]

Can you give me more instructions on how to do this? I followed a tutorial to make the simulation, I don't know where I can check if the elements are really hybridized

 

[FEA way]

Either use Tools —> Query —> Mesh in the Assembly module or write the input file (right-click on the name of the job and select Write Input), open it with any text editor, search for TYPE and check all the occurrences to see the element types (*ELEMENT, TYPE=…) used in your model.

 

[sevs]

Thanks for the reply, I found two types of elements in the file, C3D8R and C3D10H, the second one I think is the right one with the H for Hybrid and being the same one that appears in the images I posted above, right?

With that in mind, why did another type of element appear? What should I do, I don't think redoing the modeling will help since an element that wasn't specified is appearing

Thank you in advance for your help and sorry for the delay in providing more information

 

[FEA way]

C3D8R is a first-order hex element with reduced integration while C3D10H stands for hybrid second-order tet element. As you can see, the Element Type window has Hex, Wedge and Tet tabs where you can specify types of the elements of those shapes which is important if a mixed mesh is used. You can just add H to C3D8R in the input file or switch to the hex tab and enable hybrid formulation there.

 

[sevs]

When I go to the other Hex and Wedge tabs, the hybrid element option is enabled, even my hex element is actually C3D20H and not C3D8R as shown in the input file, below I attach the image, so I believe the only remaining solution is to change it in the .inp file, right? And then try running the job again?

 

[FEA way]

Yes, that's the most reliable way. Don't you have more parts/instances ? Or maybe you selected only one region of this part. Those C3D8R elements must be present somewhere. Do the aforementioned assembly query and enable coloring based on element types to find them.