GiD forum

Dear,

I am reaching out to you regarding a problem I encountered while generating mesh for my model. The model is about a cube of concrete with a steel bar and an interface between them. I received an error message saying "There are elements with Negative Jacobian in some nodes issue".

I have previously created the same model without encountering this issue, and everything was fine. Could you please suggest some solutions to solve this problem? Additionally, I am curious if there are alternative ways to mesh the model, such as using a brick type mesh for the cube. What do you think?

For your reference, the problem type used is Atena, and I am using GID v 16.1.3d. I have attached the model in a ZIP format for your convenience.

Thank you for your time and assistance. I look forward to your response.

It is raising the message 'There are elements with negative Jacobian in some node'
because of the flat prism elements of the contact volumes.
It seems that the mesh of tetrahedra doesn't have any negative Jacobian.

You can see it with the tool: Mesh->Mesh quality
and set Quality criteria=Minimum Jacobian

the tab of Prism show Minimum Jacobian range from -5.39e-24 to 1.52e-24
this really is numerical noise, can be considered as 0 (this is normal, because the contact elements have volume zero)

About meshing it with cubes, in particular this case is topologically a prismatic shape (an extrusion), and it is possible to generate a semi-structured mesh of hexahedra: Mesh_>SemiStructured->Volumes (and a number of divisions in the extrusion direction),
by default the mesh will be of tetrahedra, can set
Mesh->Elemtype->Hexahedra I attach your GiD model meshed semi-structured:

Hello,
It seems there are some tetrahedra with jacobian negative (or almost zero). You can detect them using the Mesh-Mesh Quality tool.
They are in volume 2, and it seems that is due to streched elements in the contour surfaces. Checking it, if you assign a finner mesh to the surfaces (the long ones), the final mesh is ok.

Note that as these surfaces are part of contact volumes (the volumes number from 2 to 63), you should assign the size to the surfaces of that contact volumes. Assigning a size of 0.04 to these surfaces, for instance, the final mesh is ok.
Regards,
ABEL