Using modal analysis result and submodelling result for topology optimization

- August 11, 2020 at 11:40 pm
  
  alvincsl97
  Subscriber
  
  Hi all,
  I am working on topology optimization of wing mid ribs and one of its function is to prevent buckling of the wing skin. So I wanted to perform modal analysis on the wing skin and use it as a constraints during the optimizing process.
  Because structure with large deflection cannot be optimized in ANSYS (the system told me it cannot solve it), so I opened a submodelling module and suppressed all unnecessary parts.
- August 12, 2020 at 4:23 pm
  
  John Doyle
  Ansys Employee
  
  Hi AlvinnThanks for the question. Topology Optimization does not support prestressed modal. It appears to me that this is what you are trying to do. Below is a screen shot of the documented limitations from our Mechanical Users Guide. Having said that, you can read in a static structural and modal analysis separately into a topology optimization run to minimize compliance and frequency together if that makes sense. I would recommend you focus on a model of just one wing mid rib feature for this purpose. You could try to apply displacements at cut boundary if that makes sense. The buckling analysis of the wing skin in full assembly would have to be done in a separate model after you finish optimizing the rib.nRegards,nJohnn n
- August 13, 2020 at 3:16 pm
  
  alvincsl97
  Subscriber
  
  HI, ArraynYes, topology optimization does not support when large-deflection effects is used in Static Structural analysis. And I just performed modal analysis on the submodelling module, it turned out mode 1-3 is 0Hz, while mode 4-6 has a very small frequency. When I tried to pre-stress the submodel (as seen in screenshot), an error message said Topology Optimization does not support a solution selection that has a pre-stress condition. nnSo I'm confused on how does it work? Without pre-stressing the model, the frequency is relatively low, does that mean it does not need to take natural frequency into consideration? When people perform topology optimization with maximum frequency, how do they do it?Regards,nAlvinn
- August 17, 2020 at 7:59 pm
  
  John Doyle
  Ansys Employee
  
  Hi Alvin:nUnfortunately it is a current limitation of Topology Optimization. You could perform an optimization to minimize compliance (maximize stiffness) on a structural analysis only.nThen perform a separate pre-stressed modal analysis to validate the resulting frequency is acceptable. nRegards,nJohnn
- August 21, 2020 at 2:50 pm
  
  alvincsl97
  Subscriber
  
  nThanks for clearing things up.Regards,nAlvinn