Midside nodes connected to corner nodes

[dtf82]

I'm not a Nastran user, but I'm looking at a plot of a Nastran model. It's using 2D plane stress elements. It appears that to go from a coarser to a finer mesh, there are corner nodes connected to midside nodes. I always thought that was wrong. Does it give good results?

 

[pjhype]

While I've never done this myself, I have seen it done in the past. It should be okay to connect larger 8-node plate elements to smaller 4-node plate elements using the midside nodes provided that you do not have any gaps along the interface. This modeling technique may give you some slight variations in the stress field along the interface, but these errors should be minor.

This modeling technique is not valid if you are trying to connect larger 8-node plate elements to smaller 8-node plate elements using the midside nodes on the larger elements, as you will end up with gaps in your model.

With either case, you should check for gaps with your pre/post processor. This is done by running a coincident node check and then looking at the free edge display to see if you have any gaps.

pj