Paul, The "ChElementHexaANCF_3813" element is really a traditional 8 node hexahedral element (nodes with only position coordinates). If you Google "sphere hexahedral mesh" and look at the images, you'll see some approaches to meshing a sphere with only hexahedral elements. If you are trying to mesh an ellipsoid, one approach would be to start with the hexahedral mesh of a sphere and then scale it along the three axes to match your ellipsoid's geometry. A FEA meshing program might help here depending on how fine a mesh you need.
As for other "solid" elements, there is code for the ChElementHexaANCF_3843 element (ChElementHexaANCF_3843_MR_Damp) that implements a 2-term Mooney-Rivlin material law with a non-linear single coefficient Kelvin-Voigt damping model in the fork I used for my PhD thesis (https://github.com/taylome/chrono/tree/thesis/hyperelastics). This is based on Chrono 7 and the code requires updates to use it in Chrono 9. Also note that the ChElementHexaANCF_3843 element uses 12 coordinates per node, 3 position coordinates and 3 position vector gradient coordinate sets. The position vector gradient coordinates can make the element a little harder to use from a meshing perspective. Long term, the goal is to merge the hyperelastic code developed in this fork into the main Chrono repository after some more additional development. Best Regards, Mike Taylor On Friday, May 3, 2024 at 5:07:33 AM UTC-5 [email protected] wrote: > Hello everyone, > > I want to include an ellipsoidal geometry in my model and simulate it with > finite elements. My problem now is that I want to use a hyperelastic > material model (e.g. Mooney-Rivlin), and only the > "ChElementHexaANCF_3813" element implements that. As I take it from the > examples, you need a structured mesh where the hexahedral elements have > known dimensions, which is difficult for an ellipsoid. > > I'm quite new to FEA and have only the following ideas: > > - divide the geometry into multiple simpler boxes (don't know how to do > this automatically yet) > > - add the hyperelastic material model to the other elements > > - use an external FEM solver and implement an interface to Chrono (can't > estimate how difficult this would be) > > Maybe you can help me find the best option. > > Thank you, and kind regards, > > Paul > -- You received this message because you are subscribed to the Google Groups "ProjectChrono" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/projectchrono/d5f2a664-e9ee-4cea-9cf1-73daf6e0c23dn%40googlegroups.com.
