POOR OFFSET / MIDSURFACE IN NASTRAN ( how to clean up or repair surfaces)

[Anonymous]

Hello, people. i have 3 part question guys. thanks in advance for helping me.

First Part : Attached image part 1, its an offseted geometry by using inventor nastran but it has small faces which is creating problem while meshing. i would like to refine the geometry. is it possible to carry the offseted geometry and edit in Autodesk inventor? 

second part: second part is the offseted geometry i generated of wheel rim but while 2D shell mesh, is it possible to mesh with mixed meshing ( tria + quad) automatically without having to choose the faces? 

Third part : please see attached part 3 figure, while generating midsurface the fillet surfaces are lost. how can we repair the midsurface in inventor nastran . is there a way to connect surface or atleast connect the elements ( like ruled option in Altair hypermesh)

[John_Holtz · Accepted solution]

Hi @Anonymous 

First part. You cannot transfer the surfaces created in Nastran to the modeling environment. Instead, use the Offset command in the modeling environment. (I have done it before but do not remember what needs to be done. You may need to delete a face first to convert the solid to a surface, and then move/offset the desired faces.) It will give you more flexibility to change the resulting surfaces.

Second part. A "quad" mesh is not 100% quad elements. It will create triangular elements as needed. (I see several triangles in your mesh.)

Third part. Inventor cannot create any meshes manually. Create the surfaces in the modeling environment using the "first part". (Also check this forum and the Inventor forum for creating a surface from a solid. @Roelof.Feijen may have a description or video that shows how to do it.)

[Anonymous]

thank you very much for the reply @John_Holtz . appreciate it.
-for the first part ,its a component with varying thickness ( from 2mm to 4mm) at different levels so i think what you are suggesting is , to try and make a surface in the inventor modelling environment rather than try offset option in inventor nastran. is that correct? and if i do convert it into surface, i dont think inventor nastran can allow me idealization for different thickness for same part , isn't it?
thank you in advance !!!!

[John_Holtz · Accepted solution]

"make a surface in the inventor modelling environment rather than try offset option in inventor nastran. is that correct?" Yes, that is correct.

"I don't think inventor nastran can allow me idealization for different thickness for same part , isn't it?" What's the difference between the surface model that you create in Inventor and the "surface" model that Nastran creates? If you create them both the same, then they are the same. You will assign different thicknesses to the different faces the same way that you assign different thicknesses to the offset surfaces.

When you create shell idealizations, you select the faces to define the shell. You are not selecting the part. A single part surface model can have as many different faces as needed so that you can define the proper thickness in Nastran. (For example, a cube has 6 faces. Each face can be a different idealization with a different thickness.) For you model that looks like a chimney or stack, you may need to split the 1 surface into different surfaces along the length so that you can define the different thicknesses.