Mesh Control not Generating

[Construc01]

Hi All,

I am using Nastran 2024 and have an issue with locally refining mesh. When I apply a mesh control and then generate the mesh it does not change the mesh size. At first, I thought it was a visualization problem but have realized it is not changing the mesh for the analysis. 

I have this issue when using solid elements or shells. Recently working on a shell element, I created a point from a sketch to apply a load to it. I then used the mesh control to create a node at that point however, it does not change the mesh in this area and when I run the analysis it says "Could not find a node to apply a load. Please check FE mesh and loads!"

Is there something I am missing when creating mesh controls or is this a bug in the software/a corruption of my software? 

Thanks. 

[John_Holtz]

Hi @Construc01 

I do not do that often, but it has worked when I used it. If you model is a part file and can be shared, I suggest you attach it to the forum so that someone can check how you are doing it.  If you cannot share your specific model, maybe you can reproduce the problem in a test file.

If the model is an assembly, you can provide it and all the subassemblies and the part files. It just takes a few extra steps to create a pack and go file, and I have to find the instructions for how to do that. Oh,  here are the instructions 🙂 What files to provide when the model is needed - Autodesk Community.

John

[Construc01]

Hi John,

Please see attached assembly file. 

In the assembly are two different mesh controls: 

1. The mesh control for the point/load (Load 1)
2. A mesh control on an edge of a circle.

  I have also tried apply a load to the face of the surface (Load 3, currently not applied in the analysis) which also causes an error when trying to run the analysis. 

Thanks. 

[John_Holtz · Accepted solution]

Hi @Construc01 

Thanks for the model.

1. Mesh Control 1 applied to the sketch point is on the surface of the solid. It is not on the surface of the midplane. Maybe you were hoping the mesher would project the point onto the surface of the midplane, but it does not do that. As a result, the force is applied to a point in space that is not associated with any node, so the force is not created in the analysis. You should be able to create the sketch at the future position of the midplane. (I created a new analysis and used solids. The mesh control 1 does create a node on the surface of the solid. The force applied to the sketch point used for the mesh control is added to the analysis.)
2. Mesh Control 2 tries to create a mesh size of 10 mm around the edge of a 14 mm diameter hole. The holes are small enough that 6 sides are create around the perimeter which gives a mesh size of 7.3 mm. The mesh control is too large to make the mesh smaller than what is normally created.

I am not sure what problem you were getting with load 3. I copied it from the "Model > Loads" section of the model tree and pasted it into the analysis. It was applied to the surface of the midplane. (I thought maybe load 3 was applied to the surface of the solid instead of the surface of the shell, but it is correctly applied.) I ran the analysis, and the load is working.

Let me know what you find out.

John

[Construc01]

Thanks John,

Either the Nastran Gods are smiling on me today or it was just user error. I have fixed my issue with the mesh control applied to a point following your advice. However, the issues I was having with load 3 the last couple of days is now not an issue and works fine.   

Thanks for your help.