## Preprocessing

Topics relate to geometry, meshing, and CAD

#### Meshing Failure

• ishaniis
Subscriber

I am unable to work through this error.

The geometry file has been duly attached in IGS format

• peteroznewman
Subscriber

I opened the iges file and find a solid body that represents a tube with reinforcement at 24 stations around the tube.

This is an example of a structure that would best be converted to a midsurface model. You need the tube to be a separate solid to the reinforcement ribs.  Extract a midsurface of the tube, and a midsurface of each reinforcement rib. Then you can mesh them and bond the reinforcement ribs to the tube.

• ishaniis
Subscriber

I am new to this, I could not follow this effectively.

Can you help me with the same changes ?

• parkersheaffer
Subscriber

Your model is a tube with ribs welded inside of it, if you convert this to a midsurface model not only will it resolve your meshing issues but your model size is going to be significantly less. Anytime you have a constant thickness part(plates,tubes,etc) you can model it as a surface. When this surface is imported into mechanical and meshed it will be equivalent in thickness to the solid body you created it from.

ANSYS provides a tool in spaceclaim and design modeler to quickly create midsurfaces and assign the thickness of the solid to them. Its convientently called "Midsurface" and you will find it under the prepare tab in spaceclaim.

As i mentioned before you will need a constant thickness to correctly midsurface a part, your model in its current state does not have this so you will have to split the ribs from the tube. There are many ways to split the ribs from the tube, the method I used was creating a solid cylinder with the length and inner diameter equal to the tube and using the tool "combine" to split the bodies apart.

Due to the curvature of the tube your ribs cant be directly midsurfaced as the thickness isn't a constant 2mm anymore. These will need to be modified to midsurface. If you want you can leave the ribs as solid because it requires modifying the geometry a bit. If you choose to modify the ribs its important when you create the midsurfaces for the ribs that you select the same top(shown in blue) and bottom faces(in green) for each rib otherwise when you setup contacts you will have issues.

If you do not misurface them this does not apply.

When you import these surfaces(or surface and solids) into mechanical you will need to setup a contact to attach the ribs to the tube. To do this insert 1 bonded contact(delete any contacts automatically generated) select the tube as the target and the 48 faces of the ribs as the contact. In the window if the colored faces are not facing the each other you will need to reverse the shell face of one of the bodies, then turn on shell thickness effect.

Hopefully that helps explain the process a bit further. I have the cleaned up models if you need them but i think it might be useful to try it first yourself.

• peteroznewman
Subscriber

Welcome to the Community parkersheaffer! That is a very good and detailed explanation. I hope ishaniis can follow it.

• parkersheaffer
Subscriber

Thanks! I have used this as a resource for a while and figured I could contribute a little while i'm not busy.