CQUAD4 elements for plane stress and/or plain strain analysis?

[nino_pesic]

Hello, I have just used Editor to manually create 2D analysis model featuring only a rectangular grid with CQUAD4 elements.

The problem I encountered is that I cannot find a way to change from the plane strain to plane stress analysis. I assume that Autodesk NASTRAN analysis run produced plane strain results; 2025 Reference Manual states in Section 4, p.88-93 that CQUAD4 elements can be used as shells for membrane-bending or plain strain elements, but nothing explicitly said about plane stress analysis.

(For example, with ABAQUS it would be a simple matter of changing the element type in the deck from generalised CPE4 to CPS4.)

The only other reference I found in Remark no. 11 on PSHELL (Section 4, p.335-337) which states that for "plain stress analysis MID2 value should be set to -1), but nothing about what it should be for the plane stress analysis. I tried -1 and 0 but found no obvious differences in obtained results.

What change to the input file would need to be made to use CQUAD4 elements for plane stress and plane strain analysis?

[John_Holtz · Accepted solution]

Hi @nino_pesic 

If the shell is not set to be plane strain, and if the loads cause no out-of-plane displacement, then the analysis is plane stress.

John

[nino_pesic]

Thanks @John_Holtz .

On the same topic, it appears that NASTRANs are diverging from each other in terms of commands/cards supported. For example: NX NASTRAN fact sheet mentions (among several other new features) PLOADE1 for definition of in-plane edge loads for plain stress/strain elements which does not exist in Autodesk NASTRAN.

Any plans within Autodesk to keep pace with these changes to maintain compatibility of input decks? (At least where implementation could be straightforward as might be the case with PLOADE1.)