×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

# Dissimlar Meshing of Congruent Surfaces

## Dissimlar Meshing of Congruent Surfaces

(OP)
Using Patran, I am experimenting with "Glueing" mismatched meshes.

Consider a 2D situation with 2 independent pairs of rectangular surfaces.
One pair (A) with a single common edge of the dissimilar length.
Method of surface generation was using a surface vector.
The other pair (B) with a common edge of same length, but each surface was generated
with their own set of points & curves, ie 2 points and 1 curve coincident at the common edge.
See Congruent_Meshes - Surfaces.

Mesh (A) left hand (LH) surface with Quad4 with Global Edge Length 1.
Mesh (A) right hand (RH) surface with Quad4 with Global Edge Length 0.4.
Meshes as expected.

Mesh (B) LH surface with Quad4 with Global Edge Length 1.
Mesh (B) RH surface with Quad4 with Global Edge Length 0.4.
Meshes not as expected.
See Congruent_Meshes - Meshes.

I have not found a method to get a 0.4 length rectangular mesh on the (B) RH surface.
The RH side is always influenced by the LH side mesh.
Generating B with 2 surface vectors or adding a mesh seed to the RH surface on LH side edge curve has no effect.

From Patran 2010 - Reference Manual Part 2: Geometry Modeling, page 14
Topological Congruency and Meshing

For a group of surfaces or solids to be congruent, the adjacent surfaces or solids must share common edges,
as well as common vertices.

MSC.Software Corporationâ€™s Patran software product required adjacent surfaces
or solids to share only the common vertices to be considered topologically congruent for meshing).

I see this as saying if common (coincident) points (as is the case in B) are used to define 2 surfaces, the surfaces are automatically congruent.

Anybody know how to get the meshes I require?
Any suggestions would be appreciated.

### RE: Dissimlar Meshing of Congruent Surfaces

Try disassociating the edge of surface 4 (curve 5, I think) that touches the boundary with surface 3 (curve 2).

Specifically, go to the Geometry menu and use Action: Disassociate, Object: Curve. Surfaces may be created using explicit curves or virtual curves (for example, a virtual curve going from point P to point Q, where an explicit curve is never generated). As you generated the surface from curves, you may need to disassociate both curve and surface edge. So in the Curve List dialogue, first try using "curve 5" (without quotes) and if that does not work, try "surface 4.x" where x will be the number 1,2,3 or 4 depending on the surface topology.

Once the edge of the meshable surface is disassociated, you can mesh it with impunity.

Another method we use to do this when sometimes the geometry does not want to disassociate (because other geometry depends upon it) is to create a duplicate surface at the same location as the original surface. To do this, simply use Action: Transform, Object: Surface, Method: Translate and enter <0,0,0> in the Direction Vector dialogue, and pick the surface to duplicate (surface 4 in your case).

Cheers.

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!