Error #533 Composite Size Analysis

Altair Forum User

Hi,

 

I have been working on a laminate for a Formula SAE chassis with an optimisation approach in optistruct. 

 

Currently I am stuck at the beginning of the continuous size solve. After editing my plys and adjusting the stack to a manufacturable laminate I have come across the following error: 

ERROR # 533  Repeated independent DESVAR on DLINK -2. 

 

I am unsure what could be the cause of this issue and any advice would be greatly appreciated. 

 

Thanks

 

Daniel

 

 

Altair Forum User

Hi Daniel,

 

So you just changed the laminate thickness and everything is left as it is correct?

 

Does the total laminate thickness matches with the number plies*thickness of plies?

Altair Forum User

Hi Prakash,

 

The plys in the model match the laminate thickness, I have just changed the shape to make the shape more manufactuable and have left thickness as it was. 

 

I haven't removed any plys or attempted to enforce any additional manufacturing constraints (other than limits for the continuous size solve). After my free size solve the 200,300 and 400 level plys were lumped at the bottom of my laminate (underneath the base laminate which was not altered in free size) So all I mean by adjusting the stack is placing these plys in a symmetric lay up both sides of the core. 

 

Thanks,

 

Daniel

Altair Forum User

Daniel,

 

So you just moved the plies within the laminate correct?

 

I think this broke the link between Design varibales. 

 

You can actually do a shuffling optimization at the end to get the right layup. 

Altair Forum User

Prakash,

 

I had a previous version of the model from before I rearranged the laminate. In this case I get a new error # 532: Independent Desvar on DLINK -2 is also declared dependent through DCOMP BALANCE constraints. I think my confusion has come as a result of attempting to constrain the inner and outer plys of my model to be the same during free size. as it now tries to relate these balance constraints through sets? 

 

Thanks,

 

Daniel

Altair Forum User

Daniel,

 

Could be...

 

Can you check if you break the Balance link works?

Altair Forum User

Prakash,

 

Breaking the balance between sets and replacing it with a simple 45,-45 angle balance results in the original error. breaking the balance completely leads to a massive increase in the memory required for the job.

Altair Forum User

Hi Daniel,

 

Can you share the Freesize deck and the deck which you modified?

 

Please use the dropbox link to share the files. 

Altair Forum User

Thanks Prakash,

 

I have sent the files to you.

Altair Forum User

Hi Daniel,

I checked with experts and here are their comments:

 

The error is related to the fact that there is CONST constraint and at the same time BALANCE is created. Note: there are also DESVARs where the lower bound and upper bound are the same, in this case, we internally freeze the design variable, which is the same effect as BALANCE.

 

There are more 45 degree orientation than -45 degree orientation. What kind of balance constraints do you expect with 45/-45 balance in this case? Instead of using BYANG for balance, it may make sense to use BYPLAY to create the necessary BALANCE constraints for the pair of 45 and -45.

 

Thanks,