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Minimum Ply Thickness ignored during optimization

Hello everyone,

Sorry for bothering you again, but I encountered another issue which I am not able to resolve.

I apply a thick Laminate of 72 plies to my part and let it run an optimization. However elements with no stresses should receive ply thicknesses of 0, alas 'deleting' them.

The Problem is, the lowest optistruct will go is 0.1% of the thickest ply. Say if my individual plies are is 5mm thick, the thinnest my plies will become is 0.05mm. This seems like to issue at first, but when working with 72 plies, this Comes out to a total of 0,36mm, which is indeed quite a lot!

Is there any workaroudn for this? Using the PLYMIN FUnction in the FreeSIze Design variable yields no success (Presumably because it is set to 0.0 by Default).

Any help would be greatly apprechiated.

Greetings,

Lenny

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Rahul Rajan_21763

Please refer below post for similar query.

Altair Forum User

Hello Rahul,,

Thank you for your answer!
Although I am sorry but this does not quite cover the issue that I am having. I understand that FreeSize Optimization does sometimes yield weird non-discrete ply thicknesses.

So I might rephrase my question:

is it a known phenomen that during optimization the minimum ply thickness doesnever go lower than 0.1% of the original ply thickness

OR
Is this a visualisation issue within HyperView? if you may, please look at some optimizations and the lowest displayed values in HyperView. Does it ever go to 0mm? If not, Optistruct either never reduces the plies to 0mm thickness or it is displayed inaccurately in HyperView.

Altair Forum User

Hi @Lenny

In OptiControls check the TMINPLY and set the same to zero and check if this helps.

Altair Forum User

Hello,

Thank you for your Suggestion, but that was not it. However, I found the Problem, which was kinda weird.

TMINPLY was set to Zero as Default. However, I noticed another value in the opticontrol Panel coinciding with the value that was off: The Minimum Density.

The Minimum Density is set to 0.01 as Default and thus, plies in the FreeSize-Optimization do not go lower than 1% of their original thickness.

This is however illogical and plain wrong. The density of the plies does never change in the FreeSize optimization.

So applying this Opti-Control Value to this optimization type is both illogical and confusing and I believe this should not be intentional.

Do you believe this is supposed to be this way, even though FreeSize does have nothing to do with element density?
I fixed it for me so it does not affect me anymore, but do you think I should contact Altair for a potential bug Report?

(I am not using the most recent Version so I am not sure if this happens in the recent Versions as well)

Thank you for your help! /emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20' />

Regards,

Lenny

Altair Forum User

Hi Lenny,

Thank you for sharing your findings. I am in an assumption that TMINPLY will overwrite Minimum Density factor.

I need to check if this is the way it is or a bug.