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cquad4k elements in Hypermesh?

Hi there,

I'm trying to model a very thin plate, something around the order of w/d =~500. I understand that this falls well into the Kirchhoff plate theory range rather than a Mindlin plate theory application. It's also my understanding that cquad4k elements are preferable to cquad4 elements for very thin plates as they include membrane and bending stiffness, but do not include flexibility for transverse shear deformations.

So my questions are:

1) How do I use cquad4k elements in Hypermesh?

and 2) If it's not possible, what is the best way to model very thin plates in Hypermesh?

Thanks!

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Altair Forum User

no thoughts?

Altair Forum User

Hello,

only some common words:

Element types depending from solver, not Hypermesh.

Same answer for modelling thin plates.

Regards,

Mario

Altair Forum User

Thanks for the reply, but I don't really understand what you mean. Are you saying that this is a solver issue, not a hypermesh issue? If that's the case, could you please lend me your ears anyway?

I'm using hypermesh and optistruct to solve. I'm using cquad4 elements.

It's my understanding that for thin plates (kirchhoff plates) I set mid3 to blank in my pshell card, so that transverse shear stiffness isn't considered.

It's also my understanding that for very very thin plates (membranes) I also set mid2 to blank in my pshell card, so that material bending stiffness isn't considered either, I'm just left with the membrane stiffness.

Does that make sense? I get very junky results as soon as I set both mid2 and mid3 to blank. /emoticons/default_sad.png' alt=':(' srcset='/emoticons/sad@2x.png 2x' width='20' height='20'>

Altair Forum User

Hello,

for Optistruct the following behavior are valid:

- To model a membrane plate, use only MID1

- To model a plate with bending stiffness only, use only MID2

- For bending with transverse shear flexibility, use MID2 and MID3

- Use MID3 to include an extra shear term in the element stiffness calculations (i.e. includes transverse shear flexibility).

- For a solid homogeneous plate, MID1, MID2, and MID3 should reference the same material ID

- MID4: The MID4 field (bending and membrane deformation coupling) should be defined only if the element’s cross section is unsymmetric. Default is blank = symmetric cross section.

(Note: Mass is not calculated if MID1 is blank.)

In summary, the results of leaving an MID field blank are:
●MID1: No membrane or coupling stiffness or Mass
●MID2: No bending, coupling, or transverse shear stiffness
●MID3: No transverse shear flexibility
●MID4: No bending-membrane coupling

The standard for typical shells (thickness about 1/15 of size) is to use the same ID for MID1, MID2 and MID3.

Regards,

Mario