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About Galerkin

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    FEM, CFD, CAD, Aviation, Space
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  1. Any ideas how I can solve this problem? Here is the out-file, if it helps: freesize.txt It looks like the free-size optimization does not "see" the buckling constrain at all, the results are getting worse after iterations
  2. Hi Raul, thank you! I did exactly what the "how can I assign material fraction" FAQ is recommending. I don't see how this is helping, MATINIT in DOPTPRM is set to 0.3. What do you mean exactly? Best regards, Galerkin
  3. Hey, I'm using OptiStruct as solver and I want to do a topology optimization. The initial mass is about 2.9xx tons, I'm using a a MATINIT parameter of 0.3. The solver is obviously ignoring it. After the first iteration the solver is still using 2.9xx tons. What is going on here? Why is the parameter ignored? Thank you! Galerkin
  4. Hello, I tried to variate the input parameters of my current free-size optimization project. I used starting thickness values of the properties which have proven to be successful before, this is delivering a feasible result with a mass of 400 kg. The optimization goal is to minimize the mass with a constrained buckling factor above 1 and a stress parameter. Let's say my input thicknesses are not the ideal solution. For this purpose, I tried very large thickness parameters as input, so that the solver can vary them. Instead of 20 mm, I used 100 mm for instance. This is then leading to an unfeasible result, which is (not much but still) violating the buckling constraints. A mass of 200 kg can be achieved. Can anyone please help me to understand what went south here? I gave the solver more material and more freedom to variate the design variables (=elements), but it couldn't deliver a feasible result. The problem was less constrained than the initial problem. So I expected a better result. Thank you!
  5. Hi Prakash, the problem is the following: if I use a large thickness, buckling modes are not found in the optimization. If I use a small thickness, buckling is dominant and no feasible solution will be the output. What can I do to omit this problem? I didn't get any useful results. http://i.imgur.com/Ufniy0H.png Thank you Galerkin
  6. Hello, I would like to get right of the .res file automatically, since I have no use for it and it is using a lot of space. Is there any option available for this? Thank you, Galerkin
  7. Hi, can I merge these surfaces, like seen on the attached screenshot? Thank you!
  8. The load direction should exactly cause buckling. Most critical / relevant load cases were selected, like this |-. Sorry but this can't be the problem in this case.
  9. Can you please post the ".out" and ".stat" file of your FEM problem?
  10. Hello sbx626, thanks for your support! I think the setup is okay. Now I get displacement, stress and buckling values. The CBAR/STRESS under result type of the contour plot is showing negative values. What does that mean? Here are a few screenshots, with obtained results: Thank you! Dave
  11. What can I do in practice to solve the "-lambda" problem?
  12. Hi sbx626, linear buckling is defined. The buckling loadstep is working and delivers results for 2D elements. But there are no solutions for all used 1D elements Thanks for your support, Dave
  13. Thank you, that explains a lot. What I still don't get is the physical background. If we agree that lambda=Fref/Fact, and we have only magnitudes and not vectors in this equation, how can we possibly obtain a negative figure?
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