Software Use > Analyzing & Optimizing Composite Layups

Hard to understand HyperSizer calculation in sandwich optimization

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iankim:
On the option tab, sandwich midplane(second one) is chosen.
So this is not the issue.

There wasn't big bending moment originally.
But I suppose moment gets to increase as iteration
progresses, to balance the uneven load between
top and bottom facesheet,
plus the effect of the increase of honeycomb thickness.

I attached the load distribution of the panel(A_3) I posted earlier
to comply your request.
They are external load, internal load and internal moment
calculated from Nastran freebody repectively.
All loads are just vertical nodal loads originally as shown in *ExtLoad.jpg.

The last one indicates the boundary condition on the whole wing
and A_3 is the part of yellow area.
You may think it is influenced by DOF 135 fixed nodes but it's not true,
because A_3 is not the only problematic panel.
A_7 and A_8 which are away from root BC are showing similar tendency
for example.

Do you think I have to ignore moment during iteration?
I tried to optimize the model with unstiffened and stiffened concept earlier
but there wasn't any problem in convergence.
(Total weight decreased gradually and rapidly converged to some value
after a couple of iterations)
Only this sandwich concept optimization produces this phenomenon
even with the same FE model.
What do you think I have to do to solve it?

Phil:
Its really hard to tell what could be causing this behavior.  I can see where a bending moment is being introduced from your forces but I'm not sure why it would not be converging.  If you send the FEM, I might be able to look at it.  I would only need the bulk data file and any include files, but would not need the *.F06 file.

iankim:
I sent you the bulk data file by email.
Please check your email box.
Thanks.

iankim:
While you're investigating the bulk data file,
I'm posting the convergence graph from HyperSizer analysis result of several design concepts.
While unstiffened and stiffened concepts show fast and downward convergence,
sandwich concept show slow and upward convergence.

I'm wondering if this is general phenomenon caused from HyperSizer calculation algorithm
or it's just specific to this model.
Any idea of yours?

Phil:
I think this behavior is specific to this particular model.  The loads on this particular panel are such that one facesheet wants to load up while the other face does not.  I could see from the forces you sent earlier that a substantial bending moment is introduced to the panels.  If you also have in-plane loads, this would mean that the loads on one face would be alleviated and the loads on the other face enhanced, which could cause this behavior.  I can see from your plots that the solution is essentially converged at about 7 iterations.

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