Natural frequency constraint
Altair Employee Hi, i'm having a problem with my optimisation. I have created a panel mesh, and tried to constrain it's natural frequency to 0.1Hz,using the EIGRL card in load collectors. and want to optimise the volume fraction. But I always get errors.
Thank you
Answers
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Hi Rowan,
Can you share the error message?
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* ERROR # 24 ***
Eigenvalue SUBCASES or acceleration loads exist,
and all referenced material densities are zero.0 -
Hi Rowan,
Can you input density in the material cards along with E, G/Nu?
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Hi again, i have put density in. Now the error has changed to :
*** ERROR # 1861 ***
Equality constraints can only be defined when the SQP or BIGOPT
optimization method is selected on the DOPTPRM OPTMETH card.i don't know where to find these cards.
Thanks0 -
Hi Rowan,
I am not sure what the responses are but from the error message I can suggest the following:
Go to >> Analysis>> Optimization>> OptiConrtol>> OPTMETH and change it to SQP from MFD
<?xml version="1.0" encoding="UTF-8"?>
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OKay, thank you this has worked and gained some results, just i have one other problem now: I have a panel with two thin aluminium sheets either side of the aluminium panel core, i want to optimise the cores volume fraction, but when i got to the results it removes the whole core, which i need some to still be there. Is there any way i can tell hyper mesh not to remove the whole core?
Thank You0 -
Rowan,
What are the design constraints you have?
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The constraint is natural frequency, I want to keep it within a certain value, while reducing the volume. Yet I want to keep it's overall dimensions, just change the structure of the core.
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Hi Rowan,
Have you tried changing the ISO contour threshold value in HyperView?
Can you share the model if possible?
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I have changed the ISO contour values - and there is only either full panel core with no volume removed ( the first picture shows this, the top non designable sheet has been removed from view ) it shows no panel core which should be in blue. The second picture is the meshed model in HyperWorks.
Thank you, and sorry about late reply!
<?xml version="1.0" encoding="UTF-8"?>
<?xml version="1.0" encoding="UTF-8"?>
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Hi Rowan,
sorry for a late reply.
Can you share the model with me?
You can use the dropbox link in my signature below to share the model.
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Okay, Also i made a mistake in describing my problem - meant to say I want to minimise natural frequency.
I have shared the model0 -
Hi Rowan,
Can you share the .hm or .fem file instead of .mvw file?
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Yes, sorry.I have included the .hm one
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Rowan,
Do you want to reduce the natural frequency of the entire structure?
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yes, reduce natural frequency of the whole structure, with upper and lower boundary of the volume fraction as around 0.2 and 0.3 respectively
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you can add ribs to reduce NF.Since it is a simple model.you can easily add ribs. See attached screenshot.
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